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	diff --git a/bin/increment-version b/bin/increment-version
	index 169ffae..233b6e7 100755
	--- a/bin/increment-version
	+++ b/bin/increment-version
	@@ -1,95 +1,95 @@
	#!/bin/bash

	# Based on https://github.com/fmahnke/shell-semver
	# The MIT License (MIT)
	# Copyright (c) 2014 Fritz Mahnke
	# Increment a version string using Semantic Versioning (SemVer) terminology.
	# Parse command line options.


	while getopts ":Mmpa:" Option
	do
	case $Option in
	M ) major=true;;
	m ) minor=true;;
	p ) patch=true;;
	a ) alpha=${OPTARG};;
	esac
	done

	shift $(($OPTIND - 1))

	STAGED_COUNT=$(git diff --cached --numstat \| wc -l)
	UNSTAGED_COUNT=$(git diff --numstat \| wc -l)

	## TODO check we are on master
	if [ $STAGED_COUNT -ne "0" ]; then
	echo "you have staged changes. Aborting".
	exit 1
	fi

	if [ $UNSTAGED_COUNT -ne "0" ]; then
	echo "you have unstaged changes. Aborting".
	exit 1
	fi

	version="$(mix run --no-compile --no-start -e ":io.format('~s', [PrometheusEx.Mixfile.project()[:version]])")"

	echo "Old version: ${version}"

	# Build array from version string.
	oa=( ${version//./ } )
	a=( ${version//./ } )

	# If version string is missing or has the wrong number of members, show usage message.

	if [ ${#a[@]} -ne 3 ]
	then
	echo "usage: $(basename $0) [-Mmp] TAG_MESSAGE(optional)"
	exit 1
	fi

	# Increment version numbers as requested.

	if [ ! -z $major ]
	then
	((a[0]++))
	a[1]=0
	a[2]=0
	fi

	if [ ! -z $minor ]
	then
	((a[1]++))
	a[2]=0
	fi

	if [ ! -z $patch ]
	then
	((a[2]++))
	fi

	if [ -z ${alpha+x} ];
	then
	new_version="${a[0]}.${a[1]}.${a[2]}";
	else
	new_version="${a[0]}.${a[1]}.${a[2]}.alpha-$alpha";
	fi

	echo "New version: ${new_version}"

	-sed -i s/\"${oa[0]}\.${oa[1]}\.${oa[2]}\"/\"${a[0]}\.${a[1]}\.${a[2]}\"/g mix.exs
	+sed -i s/\"${oa[0]}\.${oa[1]}\.${oa[2]}\"/\"$new_version\"/g mix.exs
	sed -i s/\~\>\ ${oa[0]}\.${oa[1]}/\~\>\ ${a[0]}\.${a[1]}/g README.md

	git add mix.exs
	git add README.md
	git add doc
	git commit -m "Bump to v${new_version}"

	TAG_MESSAGE=${1:-"New version: v${new_version}"}

	git tag -a "v${new_version}" -m "${TAG_MESSAGE}"
	git push origin master
	git push origin "v${new_version}"

	mix hex.publish
	diff --git a/lib/prometheus.ex b/lib/prometheus.ex
	index 901ac30..8eff2f5 100644
	--- a/lib/prometheus.ex
	+++ b/lib/prometheus.ex
	@@ -1,119 +1,117 @@
	defmodule Prometheus do
	- @moduledoc"""
	+ @moduledoc """

	[Prometheus.io](https://prometheus.io) client library powered by
	[prometheus.erl](https://hexdocs.pm/prometheus)

	Prometheus.ex is a thin, mostly macro-based wrapper around prometheus.erl.
	While it's pretty straightforward to use prometheus.erl from Elixir,
	you might prefer prometheus.ex because it gives you:

	- native Elixir syntax;
	- native Elixir exceptions;
	- configuration helpers that are really handy if you plan to write your custom
	instrumenter.

	```elixir
	defmodule ExampleInstrumenter do
	use Prometheus ## require common Prometheus modules, also alias metrics.

	def setup do
	Histogram.new([name: :http_request_duration_milliseconds,
	labels: [:method],
	buckets: [100, 300, 500, 750, 1000],
	help: "Http Request execution time"])
	end

	def instrument(%{time: time, method: method}) do
	Histogram.observe([name: :http_request_duration_milliseconds,
	labels: [method]],
	time)
	end
	end

	```

	## Integrations
	- [Ecto Instrumenter](https://hex.pm/packages/prometheus_ecto);
	- [Elixir plugs Instrumenters and Exporter](https://hex.pm/packages/prometheus_plugs);
	- [Fuse plugin](https://github.com/jlouis/fuse#fuse_stats_prometheus)
	- [OS process info Collector](https://hex.pm/packages/prometheus_process_collector)
	(linux-only);
	- [Phoenix Instrumenter](https://hex.pm/packages/prometheus_phoenix);
	- [RabbitMQ Exporter](https://github.com/deadtrickster/prometheus_rabbitmq_exporter).

	## Erlang VM Collectors
	- [Memory Collector](vm-memory-collector.html);
	- [Statistics Collector](vm-statistics-collector.html);
	- [System Information Collector](vm-system-info-collector.html).

	## API

	API can be grouped like this:

	### Standard Metrics & Registry

	- `Prometheus.Metric.Counter` - counter metric, to track counts of events or running
	totals;
	- `Prometheus.Metric.Gauge` - gauge metric, to report instantaneous values;
	- `Prometheus.Metric.Histogram` - histogram metric, to track distributions of events;
	- `Prometheus.Metric.Summary` - summary metric, to track the size of events;
	- `Prometheus.Registry` - working with Prometheus registries.

	All metrics created via `new/1` or `declare/1` macros. The difference is that `new/1`
	actually wants metric to be new and raises `Prometheus.MFAlreadyExistsError`
	if it isn't.

	Both `new/1` and `declare/1` accept options as
	[Keyword](http://elixir-lang.org/docs/stable/elixir/Keyword.html).
	Common options are:

	- name - metric name, can be an atom or a string (required);
	- help - metric help, string (required);
	- labels - metric labels, label can be an atom or a string (default is []);
	- registry - Prometheus registry for the metric, can be any term. (default is :default)

	Histogram also accepts `buckets` option. Please refer to respective modules docs
	for the more information.

	### General Helpers

	- `Prometheus.Buckets` - linear or exponential bucket generators;
	- `Prometheus.Contrib.HTTP` - helpers for HTTP instrumenters.

	### Integration Helpers

	- `Prometheus.Config` - provides standard configuration mechanism
	for custom instrumenters/exporters.

	### Exposition Formats

	- `Prometheus.Format.Text` - renders metrics for a given registry
	(default is `:default`) in text format;
	- `Prometheus.Format.Protobuf` - renders metrics for a given registry
	(default is `:default`) in protobuf v2 format.

	### Advanced

	You will need this modules only if you're writing custom collector for app/lib
	that can't be instrumented directly.

	- `Prometheus.Collector` - exports macros for managing/creating collectors;
	- `Prometheus.Model` - provides API for working with underlying Prometheus models.
	You'll use that if you want to create custom collector.

	"""

	defmacro __using__(_opts) do
	-
	quote do
	require Prometheus.Collector
	require Prometheus.Registry
	require Prometheus.Buckets
	use Prometheus.Metric
	require Prometheus.Contrib.HTTP
	require Prometheus.Contrib.Mnesia
	end
	end
	-
	end
	diff --git a/lib/prometheus/buckets.ex b/lib/prometheus/buckets.ex
	index ff85427..b1973f5 100644
	--- a/lib/prometheus/buckets.ex
	+++ b/lib/prometheus/buckets.ex
	@@ -1,53 +1,21 @@
	defmodule Prometheus.Buckets do
	@moduledoc """
	Histogram buckets generators.
	"""

	use Prometheus.Erlang, :prometheus_buckets

	@doc """
	- Default histogram buckets:
	+ iex(2)> Prometheus.Buckets.new(:default)
	+ [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10, :infinity]

	- iex(2)> Prometheus.Buckets.default()
	- [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10]
	+ iex(3)> Prometheus.Buckets.new({:exponential, 100, 1.2, 3})
	+ [100, 120, 144, :infinity]

	- Please note these buckets are floats and represent seconds so you'll have to use
	- `Prometheus.Metric.Histogram.dobserve/2` or configure duration_unit as `:seconds`.
	-
	- """
	- defmacro default do
	- Erlang.call()
	- end
	-
	- @doc """
	- Creates `count` buckets, where the lowest bucket has an
	- upper bound of `start` and each following bucket's upper bound is `factor`
	- times the previous bucket's upper bound. The returned list is meant to be
	- used for the `:buckets` key of histogram constructors options.
	-
	- iex(2)> Prometheus.Buckets.exponential(100, 1.2, 3)
	- [100, 120, 144]
	-
	- The function raises `Prometheus.InvalidValueError` if `count` is 0 or negative,
	- if `start` is 0 or negative, or if `factor` is less than or equals to 1.
	+ iex(2)> Prometheus.Buckets.new({:linear, 10, 5, 6})
	+ [10, 15, 20, 25, 30, 35, :infinity]
	"""
	- defmacro exponential(start, factor, count) do
	- Erlang.call([start, factor, count])
	+ defmacro new(arg) do
	+ Erlang.call([arg])
	end
	-
	- @doc """
	- Creates `count` buckets, each `width` wide, where the lowest
	- bucket has an upper bound of `start`. The returned list is meant to be
	- used for the `:buckets` key of histogram constructors options.
	-
	- iex(2)> Prometheus.Buckets.linear(10, 5, 6)
	- [10, 15, 20, 25, 30, 35]
	-
	- The function raises `Prometheus.InvalidValueError` exception
	- if `count` is zero or negative.
	- """
	- defmacro linear(start, step, count) do
	- Erlang.call([start, step, count])
	- end
	-
	end
	diff --git a/lib/prometheus/collector.ex b/lib/prometheus/collector.ex
	index 9071cc0..b3d4bf8 100644
	--- a/lib/prometheus/collector.ex
	+++ b/lib/prometheus/collector.ex
	@@ -1,94 +1,90 @@
	defmodule Prometheus.Collector do
	@moduledoc """
	A collector for a set of metrics.

	Normal users should use `Prometheus.Metric.Gauge`, `Prometheus.Metric.Counter`,
	`Prometheus.Metric.Summary`
	and `Prometheus.Metric.Histogram`.

	Implementing `:prometheus_collector` behaviour is for advanced uses such as proxying
	metrics from another monitoring system.
	It is the responsibility of the implementer to ensure produced metrics are valid.

	You will be working with Prometheus data model directly (see `Prometheus.Model` ).

	Callbacks:
	- `collect_mf(registry, callback)` - called by exporters and formats.
	Should call `callback` for each `MetricFamily` of this collector;
	- `collect_metrics(name, data)` - called by `MetricFamily` constructor.
	Should return Metric list for each MetricFamily identified by `name`.
	`data` is a term associated with MetricFamily by collect_mf.
	- `deregister_cleanup(registry)` - called when collector unregistered by
	`registry`. If collector is stateful you can put cleanup code here.

	Example (simplified [`:prometheus_vm_memory_collector`](https://github.com/deadtrickster/prometheus.erl/blob/master/doc/prometheus_vm_memory_collector.md)):

	```
	iex(3)> defmodule Prometheus.VMMemoryCollector do
	...(3)> use Prometheus.Collector
	...(3)>
	...(3)> @labels [:processes, :atom, :binary, :code, :ets]
	...(3)>
	...(3)> def collect_mf(_registry, callback) do
	...(3)> memory = :erlang.memory()
	...(3)> callback.(create_gauge(
	...(3)> :erlang_vm_bytes_total,
	...(3)> "The total amount of memory currently allocated.",
	...(3)> memory))
	...(3)> :ok
	...(3)> end
	...(3)>
	...(3)> def collect_metrics(:erlang_vm_bytes_total, memory) do
	...(3)> Prometheus.Model.gauge_metrics(
	...(3)> for label <- @labels do
	...(3)> {[type: label], memory[label]}
	...(3)> end)
	...(3)> end
	...(3)>
	...(3)> defp create_gauge(name, help, data) do
	...(3)> Prometheus.Model.create_mf(name, help, :gauge, __MODULE__, data)
	...(3)> end
	...(3)> end
	iex(4)> Prometheus.Registry.register_collector(Prometheus.VMMemoryCollector)
	:ok
	iex(5)> r = ~r/# TYPE erlang_vm_bytes_total gauge
	...(5)> # HELP erlang_vm_bytes_total
	...(5)> The total amount of memory currently allocated.
	...(5)> erlang_vm_bytes_total{type=\"processes\"} [1-9]
	...(5)> erlang_vm_bytes_total{type=\"atom\"} [1-9]
	...(5)> erlang_vm_bytes_total{type=\"binary\"} [1-9]
	...(5)> erlang_vm_bytes_total{type=\"code\"} [1-9]
	...(5)> erlang_vm_bytes_total{type=\"ets\"} [1-9]/
	iex(6)> Regex.match?(r, Prometheus.Format.Text.format)
	true
	```
	"""

	defmacro __using__(_opts) do
	-
	quote location: :keep do
	@behaviour :prometheus_collector

	require Prometheus.Error
	require Prometheus.Model

	def deregister_cleanup(_registry) do
	:ok
	end

	- defoverridable [deregister_cleanup: 1]
	-
	+ defoverridable deregister_cleanup: 1
	end
	-
	end

	use Prometheus.Erlang, :prometheus_collector

	@doc """
	Calls `callback` for each MetricFamily of this collector.
	"""
	defmacro collect_mf(registry \\ :default, collector, callback) do
	Erlang.call([registry, collector, callback])
	end
	-
	end
	diff --git a/lib/prometheus/config.ex b/lib/prometheus/config.ex
	index 97ac266..76d9408 100644
	--- a/lib/prometheus/config.ex
	+++ b/lib/prometheus/config.ex
	@@ -1,91 +1,93 @@
	defmodule Prometheus.Config do
	-
	@moduledoc """

	Configuration templates for custom collectors/exporters.

	When `use`ed, generates accessor for each configuration option:

	iex(4)> defmodule MyInstrumenter do
	...(4)> use Prometheus.Config, [:required_option,
	...(4)> registry: :default]
	...(4)> end
	iex(5)> MyInstrumenter.Config.registry(MyInstrumenter)
	:default
	iex(6)> MyInstrumenter.Config.required_option!(MyInstrumenter)
	** (Prometheus.Config.KeyNotFoundError) mandatory option :required_option not found in PrometheusTest.MyInstrumenter instrumenter/collector config
	iex(7)> Application.put_env(:prometheus, MyInstrumenter,
	...(7)> [required_option: "Hello world!"])
	:ok
	iex(8)> MyInstrumenter.Config.required_option!(MyInstrumenter)
	"Hello world!"

	"""

	defmodule KeyNotFoundError do
	@moduledoc """
	Raised when mandatory configuration option not found in app env.
	"""
	defexception [:option, :key]

	def message(%{option: option, key: key}) do
	friendly_key_name = String.replace_leading("#{key}", "Elixir.", "")
	+
	"mandatory option :#{option} not found" <>
	" in #{friendly_key_name} instrumenter/collector config"
	end
	end

	defmacro __using__(default_config) do
	-
	- keyword_default_config = Enum.reject(default_config, fn(option) ->
	- case option do
	- {_, _} -> false
	- _ -> true
	- end
	- end)
	+ keyword_default_config =
	+ Enum.reject(default_config, fn option ->
	+ case option do
	+ {_, _} -> false
	+ _ -> true
	+ end
	+ end)

	quote do
	defmodule Config do
	@moduledoc false

	def config(key) do
	Application.get_env(:prometheus, key, unquote(keyword_default_config))
	end

	defp config(key, option, default) do
	key
	\|> config()
	\|> Keyword.get(option, default)
	end

	defp config(key, option) do
	key
	\|> config()
	\|> Keyword.fetch!(option)
	rescue
	- # credo:disable-for-next-line Credo.Check.Warning.RaiseInsideRescue
	- e in KeyError -> raise %KeyNotFoundError{key: key, option: option}
	+ e in KeyError ->
	+ # credo:disable-for-next-line Credo.Check.Warning.RaiseInsideRescue
	+ raise %KeyNotFoundError{key: key, option: option}
	end

	unquote do
	for config <- default_config do
	case config do
	{option, default} ->
	quote do
	def unquote(option)(key) do
	config(key, unquote(option), unquote(default))
	end
	end
	+
	option ->
	quote do
	def unquote(:"#{option}!")(key) do
	config(key, unquote(option))
	end
	end
	end
	end
	end
	end
	end
	end
	end
	diff --git a/lib/prometheus/contrib/http.ex b/lib/prometheus/contrib/http.ex
	index 26986d7..694c6a3 100644
	--- a/lib/prometheus/contrib/http.ex
	+++ b/lib/prometheus/contrib/http.ex
	@@ -1,34 +1,32 @@
	defmodule Prometheus.Contrib.HTTP do
	@moduledoc """
	HTTP instrumentation helpers
	"""

	@doc """
	Returns default microseconds buckets for measuring http requests duration:

	iex(6)> Prometheus.Contrib.HTTP.microseconds_duration_buckets
	[10, 25, 50, 100, 250, 500, 1000, 2500, 5000, 10000, 25000, 50000,
	100000, 250000, 500000, 1000000, 2500000, 5000000, 10000000]

	"""
	defmacro microseconds_duration_buckets do
	- :prometheus_http.microseconds_duration_buckets
	+ :prometheus_http.microseconds_duration_buckets()
	end

	@doc """
	Returns class of the http status code:

	iex(7)> Prometheus.Contrib.HTTP.status_class(202)
	'success'

	Raises `Prometheus.InvalidValueError` exception if `code` is not a positive integer.
	"""
	defmacro status_class(code) do
	quote do
	require Prometheus.Error
	- Prometheus.Error.with_prometheus_error(
	- :prometheus_http.status_class(unquote(code))
	- )
	+ Prometheus.Error.with_prometheus_error(:prometheus_http.status_class(unquote(code)))
	end
	end
	end
	diff --git a/lib/prometheus/contrib/mnesia.ex b/lib/prometheus/contrib/mnesia.ex
	index c333b09..5bdcec2 100644
	--- a/lib/prometheus/contrib/mnesia.ex
	+++ b/lib/prometheus/contrib/mnesia.ex
	@@ -1,35 +1,40 @@
	defmodule Prometheus.Contrib.Mnesia do
	@moduledoc """
	Mnesia instrumentation helpers.
	"""
	use Prometheus.Erlang, :prometheus_mnesia

	@doc """
	Returns sum of all mnesia files for the given `table` in bytes.
	Mnesia can create different files for each table:
	- .DAT - DETS files
	- .TMP - temp files
	- .DMP - dumped ets tables
	- .DCD - disc copies data
	- .DCL - disc copies log
	- .LOGTMP - disc copies log

	More on Mnesia files can be found in
	<a href="http://erlang.org/doc/apps/mnesia/Mnesia_chap7.html">
	Mnesia System Information chapter
	</a> of Mnesia User's Guide
	"""
	- defmacro table_disk_size(dir \\ quote do :mnesia.system_info(:directory) end, table) do
	+ defmacro table_disk_size(
	+ dir \\ quote do
	+ :mnesia.system_info(:directory)
	+ end,
	+ table
	+ ) do
	Erlang.call([dir, table])
	end

	@doc """
	Returns {pcount, ccount} tuple, where
	pcount is a number of participant transactions and
	ccount is a number of coordinator transactions.
	Can return {:undefined, :undefined} occasionally.
	"""
	defmacro tm_info() do
	Erlang.call()
	end
	end
	diff --git a/lib/prometheus/erlang.ex b/lib/prometheus/erlang.ex
	index 7a10f02..2de0043 100644
	--- a/lib/prometheus/erlang.ex
	+++ b/lib/prometheus/erlang.ex
	@@ -1,135 +1,153 @@
	defmodule Prometheus.Erlang do
	@moduledoc false

	require Prometheus.Metric
	alias Prometheus.Metric

	defmacro __using__(erlang_module) do
	quote do
	@erlang_module unquote(erlang_module)
	alias Prometheus.Erlang
	end
	end

	defmacro call(mf \\ false, arguments \\ []) do
	{module, function, arguments} = parse_mfa(__CALLER__, mf, arguments)

	quote do
	Prometheus.Erlang.call_body(unquote(module), unquote(function), unquote(arguments))
	end
	end

	def call_body(module, function, arguments) do
	quote do
	-
	require Prometheus.Error

	Prometheus.Error.with_prometheus_error(
	- unquote(module).unquote(function)(unquote_splicing(arguments)))
	-
	+ unquote(module).unquote(function)(unquote_splicing(arguments))
	+ )
	end
	end

	defmacro metric_call(mf_or_spec, spec \\ false, arguments \\ []) do
	-
	{mf, spec, arguments} = parse_metric_call_args(mf_or_spec, spec, arguments)

	{module, function, arguments} = parse_mfa(__CALLER__, mf, arguments)

	quote do
	- Prometheus.Erlang.metric_call_body(unquote(module), unquote(function),
	- unquote(spec), unquote(arguments))
	+ Prometheus.Erlang.metric_call_body(
	+ unquote(module),
	+ unquote(function),
	+ unquote(spec),
	+ unquote(arguments)
	+ )
	end
	end

	def metric_call_body(module, function, spec, arguments) do
	-
	case spec do
	_ when Metric.ct_parsable_spec?(spec) ->
	-
	{registry, name, labels} = Prometheus.Metric.parse_spec(spec)

	quote do
	-
	require Prometheus.Error

	Prometheus.Error.with_prometheus_error(
	- unquote(module).unquote(function)(unquote(registry), unquote(name),
	- unquote(labels), unquote_splicing(arguments)))
	-
	+ unquote(module).unquote(function)(
	+ unquote(registry),
	+ unquote(name),
	+ unquote(labels),
	+ unquote_splicing(arguments)
	+ )
	+ )
	end
	+
	_ ->
	quote do
	-
	require Prometheus.Error

	{registry, name, labels} = Metric.parse_spec(unquote(spec))

	Prometheus.Error.with_prometheus_error(
	- unquote(module).unquote(function)(registry, name, labels,
	- unquote_splicing(arguments)))
	-
	+ unquote(module).unquote(function)(
	+ registry,
	+ name,
	+ labels,
	+ unquote_splicing(arguments)
	+ )
	+ )
	end
	end
	end

	defp parse_metric_call_args(mf_or_spec, spec, arguments) do
	case mf_or_spec do
	## Erlang.metric_call({:prometheus_counter, :dinc}, spec, [value])
	- {_, _} -> {mf_or_spec, spec, arguments}
	+ {_, _} ->
	+ {mf_or_spec, spec, arguments}
	+
	## Erlang.metric_call(:inc, spec, [value])
	- _ when is_atom(mf_or_spec) -> {mf_or_spec, spec, arguments}
	+ _ when is_atom(mf_or_spec) ->
	+ {mf_or_spec, spec, arguments}
	+
	_ ->
	## args are 'shifted' to left
	[] = arguments
	+
	if spec == false do
	## only spec is needed, e.g. Erlang.metric_call(spec)
	{false, mf_or_spec, []}
	else
	## Erlang.metric_call(spec, [value])
	{false, mf_or_spec, spec}
	end
	end
	end

	defp parse_mfa(__CALLER__, mf, arguments) do
	- arguments = case mf do
	- _ when is_list(mf) ->
	- [] = arguments
	- mf
	- _ ->
	- arguments
	- end
	-
	- {module, function} = case mf do
	- false ->
	- {f, _arity} = __CALLER__.function
	- {Module.get_attribute(__CALLER__.module, :erlang_module), f}
	- _ when is_list(mf) ->
	- {f, _arity} = __CALLER__.function
	- {Module.get_attribute(__CALLER__.module, :erlang_module), f}
	- {_, _} ->
	- mf
	- _ when is_atom(mf) ->
	- {Module.get_attribute(__CALLER__.module, :erlang_module), mf}
	- end
	+ arguments =
	+ case mf do
	+ _ when is_list(mf) ->
	+ [] = arguments
	+ mf
	+
	+ _ ->
	+ arguments
	+ end
	+
	+ {module, function} =
	+ case mf do
	+ false ->
	+ {f, _arity} = __CALLER__.function
	+ {Module.get_attribute(__CALLER__.module, :erlang_module), f}
	+
	+ _ when is_list(mf) ->
	+ {f, _arity} = __CALLER__.function
	+ {Module.get_attribute(__CALLER__.module, :erlang_module), f}
	+
	+ {_, _} ->
	+ mf
	+
	+ _ when is_atom(mf) ->
	+ {Module.get_attribute(__CALLER__.module, :erlang_module), mf}
	+ end

	{module, function, arguments}
	end

	def ensure_fn(var) do
	case var do
	[do: block] ->
	quote do
	fn ->
	unquote(block)
	end
	end
	+
	fun ->
	quote do
	unquote(fun)
	end
	end
	end
	-
	end
	diff --git a/lib/prometheus/error.ex b/lib/prometheus/error.ex
	index 62e0037..749dc22 100644
	--- a/lib/prometheus/error.ex
	+++ b/lib/prometheus/error.ex
	@@ -1,206 +1,220 @@
	defmodule Prometheus.InvalidValueError do
	@moduledoc """
	Raised when given `value` is invalid i.e. when you pass a negative number to
	`Prometheus.Metric.Counter.inc/2`.
	"""
	defexception [:value, :orig_message]

	def message(%{value: value, orig_message: message}) do
	- "Invalid value: #{inspect value} (#{message})."
	+ "Invalid value: #{inspect(value)} (#{message})."
	end
	end

	defmodule Prometheus.InvalidMetricNameError do
	@moduledoc """
	Raised when given metric `name` is invalid i.e. can't be represented as printable utf-8
	string that matches `^[a-zA-Z_:][a-zA-Z0-9_:]*$` regular expression.
	"""
	defexception [:name]

	def message(%{name: name}) do
	"Invalid metric name: #{name}."
	end
	end

	defmodule Prometheus.InvalidMetricLabelsError do
	@moduledoc """
	Raised when `labels` isn't a list.
	"""
	defexception [:labels]

	def message(%{labels: labels}) do
	"Invalid metric labels: #{labels}."
	end
	end

	defmodule Prometheus.InvalidMetricHelpError do
	@moduledoc """
	Raised when given metric `help` is invalid i.e. isn't a printable utf-8 string.
	"""
	defexception [:help]

	def message(%{help: help}) do
	"Invalid metric help: #{help}."
	end
	end

	defmodule Prometheus.InvalidMetricArityError do
	@moduledoc """
	Raised when metric arity is invalid e.g. counter metric was created with two labels but
	only one label value is passed to `Prometheus.Metric.Counter.inc/2`.
	"""
	defexception [:present, :expected]

	def message(%{present: present, expected: expected}) do
	"Invalid metric arity: got #{present}, expected #{expected}."
	end
	end

	defmodule Prometheus.UnknownMetricError do
	defexception [:registry, :name]

	def message(%{registry: registry, name: name}) do
	"Unknown metric {registry: #{registry}, name: #{name}}."
	end
	end

	defmodule Prometheus.InvalidLabelNameError do
	@moduledoc """
	Raised when label `name` is invalid i.e. can't be represented as printable utf-8 string
	that matches `^[a-zA-Z_][a-zA-Z0-9_]*$` regular expression or starts with `__`.

	Metric can impose further restrictions on label names.
	"""
	defexception [:name, :orig_message]

	def message(%{name: name, orig_message: message}) do
	"Invalid label name: #{name} (#{message})."
	end
	end

	defmodule Prometheus.MFAlreadyExistsError do
	@moduledoc """
	Raised when one tries to create metric in `registry` with `name` it already exists.
	"""
	defexception [:registry, :name]

	def message(%{registry: registry, name: name}) do
	"Metric #{registry}:#{name} already exists."
	end
	end

	-defmodule Prometheus.HistogramNoBucketsError do
	+defmodule Prometheus.NoBucketsError do
	@moduledoc """
	Raised by histogram constructors when buckets can't be found in spec, or
	found value is empty list.
	"""
	defexception [:buckets]

	def message(%{buckets: buckets}) do
	"Invalid histogram buckets: #{buckets}."
	end
	end

	-defmodule Prometheus.HistogramInvalidBucketsError do
	+defmodule Prometheus.InvalidBucketsError do
	@moduledoc """
	Raised by histogram constructors when buckets are invalid i.e. not sorted in increasing
	order or generator spec is unknown.
	"""
	defexception [:buckets, :orig_message]

	def message(%{buckets: buckets, orig_message: message}) do
	buckets = :io_lib.format("~p", [buckets])
	"Invalid histogram buckets: #{buckets} (#{message})."
	end
	end

	-defmodule Prometheus.HistogramInvalidBoundError do
	+defmodule Prometheus.InvalidBoundError do
	@moduledoc """
	Raised by histogram constructors when bucket bound isn't a number.
	"""
	defexception [:bound]

	def message(%{bound: bound}) do
	"Invalid histogram bound: #{bound}."
	end
	end

	defmodule Prometheus.MissingMetricSpecKeyError do
	@moduledoc """
	Raised when required metric `spec` `key` is missing. All metrics
	require at least `name` and when metric created `help`.

	Metrics can have their specific required keys.
	"""
	defexception [:key, :spec]

	def message(%{key: key}) do
	"Required key #{key} is missing from metric spec."
	end
	end

	defmodule Prometheus.InvalidBlockArityError do
	@moduledoc """
	Raised when fn passed as block has more then 0 arguments
	"""
	defexception [:args]

	def message(%{args: args}) do
	insp = Enum.map_join(args, ", ", &inspect/1)
	"Fn with arity #{length(args)} (args: #{insp}) passed as block."
	end
	end

	defmodule Prometheus.Error do
	@moduledoc false

	# credo:disable-for-this-file Credo.Check.Refactor.ABCSize
	# credo:disable-for-this-file Credo.Check.Refactor.CyclomaticComplexity
	def normalize(erlang_error) do
	case erlang_error do
	%ErlangError{original: original} ->
	case original do
	{:invalid_value, value, message} ->
	%Prometheus.InvalidValueError{value: value, orig_message: message}
	+
	{:invalid_metric_name, name, _message} ->
	%Prometheus.InvalidMetricNameError{name: name}
	+
	{:invalid_metric_help, help, _message} ->
	%Prometheus.InvalidMetricHelpError{help: help}
	+
	{:invalid_metric_arity, present, expected} ->
	%Prometheus.InvalidMetricArityError{present: present, expected: expected}
	+
	{:unknown_metric, registry, name} ->
	%Prometheus.UnknownMetricError{registry: registry, name: name}
	+
	{:invalid_metric_labels, labels, _message} ->
	%Prometheus.InvalidMetricLabelsError{labels: labels}
	+
	{:invalid_metric_label_name, name, message} ->
	%Prometheus.InvalidLabelNameError{name: name, orig_message: message}
	+
	{:mf_already_exists, {registry, name}, _message} ->
	%Prometheus.MFAlreadyExistsError{registry: registry, name: name}
	- {:histogram_no_buckets, buckets} ->
	- %Prometheus.HistogramNoBucketsError{buckets: buckets}
	- {:histogram_invalid_buckets, buckets, message} ->
	- %Prometheus.HistogramInvalidBucketsError{buckets: buckets,
	- orig_message: message}
	- {:histogram_invalid_bound, bound} ->
	- %Prometheus.HistogramInvalidBoundError{bound: bound}
	+
	+ {:no_buckets, buckets} ->
	+ %Prometheus.NoBucketsError{buckets: buckets}
	+
	+ {:invalid_buckets, buckets, message} ->
	+ %Prometheus.InvalidBucketsError{
	+ buckets: buckets,
	+ orig_message: message
	+ }
	+
	+ {:invalid_bound, bound} ->
	+ %Prometheus.InvalidBoundError{bound: bound}
	+
	{:missing_metric_spec_key, key, spec} ->
	%Prometheus.MissingMetricSpecKeyError{key: key, spec: spec}
	+
	_ ->
	erlang_error
	end
	+
	_ ->
	erlang_error
	end
	end

	defmacro with_prometheus_error(block) do
	quote do
	try do
	unquote(block)
	rescue
	- e in ErlangError -> reraise Prometheus.Error.normalize(e), System.stacktrace
	+ e in ErlangError -> reraise Prometheus.Error.normalize(e), System.stacktrace()
	end
	end
	end
	-
	end
	diff --git a/lib/prometheus/format/protobuf.ex b/lib/prometheus/format/protobuf.ex
	index 1fb4b40..1399551 100644
	--- a/lib/prometheus/format/protobuf.ex
	+++ b/lib/prometheus/format/protobuf.ex
	@@ -1,28 +1,23 @@
	defmodule Prometheus.Format.Protobuf do
	@moduledoc """
	Serializes Prometheus registry using [protocol buffer format](http://bit.ly/2cxSuJP).
	"""

	require Prometheus.Error

	@doc """
	Content type of protocol buffer format.
	"""
	def content_type do
	require Prometheus.Error
	- Prometheus.Error.with_prometheus_error(
	- :prometheus_protobuf_format.content_type
	- )
	+ Prometheus.Error.with_prometheus_error(:prometheus_protobuf_format.content_type())
	end

	@doc """
	Format `registry` (default is `:default`) using protocol buffer format.
	"""
	def format(registry \\ :default) do
	require Prometheus.Error
	- Prometheus.Error.with_prometheus_error(
	- :prometheus_protobuf_format.format(registry)
	- )
	+ Prometheus.Error.with_prometheus_error(:prometheus_protobuf_format.format(registry))
	end
	-
	end
	diff --git a/lib/prometheus/format/text.ex b/lib/prometheus/format/text.ex
	index 3a886a7..395e602 100644
	--- a/lib/prometheus/format/text.ex
	+++ b/lib/prometheus/format/text.ex
	@@ -1,41 +1,36 @@
	defmodule Prometheus.Format.Text do
	@moduledoc """
	Serializes Prometheus registry using the latest [text format](http://bit.ly/2cxSuJP).

	Example output:
	```
	# TYPE http_request_duration_milliseconds histogram
	# HELP http_request_duration_milliseconds Http Request execution time
	http_request_duration_milliseconds_bucket{method="post",le="100"} 0
	http_request_duration_milliseconds_bucket{method="post",le="300"} 1
	http_request_duration_milliseconds_bucket{method="post",le="500"} 3
	http_request_duration_milliseconds_bucket{method="post",le="750"} 4
	http_request_duration_milliseconds_bucket{method="post",le="1000"} 5
	http_request_duration_milliseconds_bucket{method="post",le="+Inf"} 6
	http_request_duration_milliseconds_count{method="post"} 6
	http_request_duration_milliseconds_sum{method="post"} 4350
	```
	"""
	require Prometheus.Error

	@doc """
	Returns content type of the latest text format.
	"""
	def content_type do
	require Prometheus.Error
	- Prometheus.Error.with_prometheus_error(
	- :prometheus_text_format.content_type
	- )
	+ Prometheus.Error.with_prometheus_error(:prometheus_text_format.content_type())
	end

	@doc """
	Formats `registry` (default is `:default`) using the latest text format.
	"""
	def format(registry \\ :default) do
	require Prometheus.Error
	- Prometheus.Error.with_prometheus_error(
	- :prometheus_text_format.format(registry)
	- )
	+ Prometheus.Error.with_prometheus_error(:prometheus_text_format.format(registry))
	end
	-
	end
	diff --git a/lib/prometheus/injector.ex b/lib/prometheus/injector.ex
	index c5083fe..0881fa6 100644
	--- a/lib/prometheus/injector.ex
	+++ b/lib/prometheus/injector.ex
	@@ -1,94 +1,110 @@
	defmodule Prometheus.Injector do
	-
	def inject(callback, env, ast) do
	ast
	- \|> Macro.prewalk(fn (thing) ->
	+ \|> Macro.prewalk(fn thing ->
	case thing do
	- {:def, _, _} = defun -> defun
	- {:in, _, _} = arrow -> arrow #otherwise e in RuntimeError will be rewritten
	- _ -> Macro.expand(thing, env)
	+ {:def, _, _} = defun ->
	+ defun
	+
	+ # otherwise e in RuntimeError will be rewritten
	+ {:in, _, _} = arrow ->
	+ arrow
	+
	+ _ ->
	+ Macro.expand(thing, env)
	end
	end)
	- \|> inject_(callback)
	+ \|> inject_(callback)
	end

	# lambda
	def inject_({:fn, fn_meta, [{:->, arrow_meta, [args, do_block]}]}, callback) do
	case args do
	[] ->
	- callback.({{:., [],
	- [{:fn, fn_meta,
	- [{:->, arrow_meta,
	- [[], do_block]}]}]}, [],
	- []})
	+ callback.(
	+ {{:., [], [{:fn, fn_meta, [{:->, arrow_meta, [[], do_block]}]}]}, [], []}
	+ )
	+
	_ ->
	- names = args
	- \|> Enum.map(fn({name, _, _}) -> name end)
	+ names =
	+ args
	+ \|> Enum.map(fn {name, _, _} -> name end)
	+
	raise Prometheus.InvalidBlockArityError, args: names
	end
	end

	# do_blocks can be simple calls or defs
	def inject_([{:do, {:__block__, [], do_blocks}}], callback) do
	do_blocks = List.flatten(do_blocks)
	+
	if have_defs(do_blocks) do
	Enum.map(do_blocks, &inject_to_def(&1, callback))
	else
	- callback.({:__block__, [], do_blocks})
	+ callback.({:__block__, [], do_blocks})
	end
	end

	# just do
	def inject_([{:do, do_block}], callback) do
	inject_([{:do, {:__block__, [], [do_block]}}], callback)
	end

	# implicit try
	def inject_([{:do, _do_block} \| rest] = all, callback) do
	if is_try_unwrapped(rest) do
	callback.(
	quote do
	try unquote(all)
	- end)
	+ end
	+ )
	else
	- raise "Unexpected do block #{inspect rest}"
	+ raise "Unexpected do block #{inspect(rest)}"
	end
	end

	# single do, or other non-block stuff like function calls
	def inject_(thing, callback) do
	inject_([{:do, {:__block__, [], [thing]}}], callback)
	end

	defp is_try_unwrapped(block) do
	- Keyword.has_key?(block, :catch)
	- \|\| Keyword.has_key?(block, :rescue)
	- \|\| Keyword.has_key?(block, :after)
	- \|\| Keyword.has_key?(block, :else)
	+ Keyword.has_key?(block, :catch) \|\| Keyword.has_key?(block, :rescue) \|\|
	+ Keyword.has_key?(block, :after) \|\| Keyword.has_key?(block, :else)
	end

	defp have_defs(blocks) do
	- defs_count = Enum.count(blocks, fn
	- ({:def, _, _}) -> true
	- (_) -> false
	- end)
	+ defs_count =
	+ Enum.count(blocks, fn
	+ {:def, _, _} -> true
	+ _ -> false
	+ end)

	blocks_count = Enum.count(blocks)

	case defs_count do
	0 -> false
	^blocks_count -> true
	_ -> raise "Mixing defs and other blocks isn't allowed"
	end
	end

	defp inject_to_def({:def, def_meta, [head, [do: body]]}, callback) do
	{:def, def_meta, [head, [do: callback.(body)]]}
	end
	+
	defp inject_to_def({:def, def_meta, [head, [{:do, _do_block} \| _rest] = all]}, callback) do
	- {:def, def_meta, [head, [do: callback.(
	- quote do
	- try unquote(all)
	- end)]]}
	+ {:def, def_meta,
	+ [
	+ head,
	+ [
	+ do:
	+ callback.(
	+ quote do
	+ try unquote(all)
	+ end
	+ )
	+ ]
	+ ]}
	end
	end
	diff --git a/lib/prometheus/metric.ex b/lib/prometheus/metric.ex
	index fe5f9ab..50ead0a 100644
	--- a/lib/prometheus/metric.ex
	+++ b/lib/prometheus/metric.ex
	@@ -1,157 +1,176 @@
	defmodule Prometheus.Metric do
	@moduledoc """

	Prometheus metrics shortcuts.

	Aliases and requires respective metric modules so they are
	accessible without `Prometheus.Metric` prefix.

	Allows to automatically setup metrics with
	`@<type`> attributes. Metrics will be declared in
	the `@on_load` callback. If the module already
	has `@on_laod` callback, metrics will be declared
	iff the callback returns `:ok`.

	iex(1)> defmodule MyCoolModule do
	...(1)> use Prometheus.Metric
	...(1)>
	...(1)> @counter name: :test_counter3, labels: [], help: "qwe"
	...(1)> end
	iex(2)> require Prometheus.Metric.Counter
	Prometheus.Metric.Counter
	iex(3)> Prometheus.Metric.Counter.value(:test_counter3)
	0

	"""

	@metrics [:counter, :gauge, :boolean, :summary, :histogram]

	defmacro __using__(_opts) do
	module_name = __CALLER__.module

	quote do
	# credo:disable-for-next-line Credo.Check.Readability.SpaceAfterCommas
	- alias Prometheus.Metric.{Counter,Gauge,Histogram,Summary,Boolean}
	+ alias Prometheus.Metric.{Counter, Gauge, Histogram, Summary, Boolean}
	# credo:disable-for-next-line Credo.Check.Readability.SpaceAfterCommas
	- require Prometheus.Metric.{Counter,Gauge,Histogram,Summary,Boolean}
	+ require Prometheus.Metric.{Counter, Gauge, Histogram, Summary, Boolean}
	require Prometheus.Error

	unquote_splicing(
	for metric <- @metrics do
	quote do
	- Module.register_attribute(unquote(module_name), unquote(metric),
	- accumulate: true)
	+ Module.register_attribute(
	+ unquote(module_name),
	+ unquote(metric),
	+ accumulate: true
	+ )
	end
	- end)
	+ end
	+ )

	@before_compile unquote(__MODULE__)
	end
	end

	defmacro __before_compile__(env) do
	quote do
	def __declare_prometheus_metrics__() do
	if List.keymember?(Application.started_applications(), :prometheus, 0) do
	- unquote_splicing(
	- for metric <- @metrics do
	- declarations = Module.get_attribute(env.module, metric)
	- Module.delete_attribute(env.module, metric)
	- quote do
	- unquote_splicing(
	- for params <- declarations do
	- emit_create_metric(metric, params)
	- end)
	- :ok
	- end
	- end)
	+ (unquote_splicing(
	+ for metric <- @metrics do
	+ declarations = Module.get_attribute(env.module, metric)
	+ Module.delete_attribute(env.module, metric)
	+
	+ quote do
	+ unquote_splicing(
	+ for params <- declarations do
	+ emit_create_metric(metric, params)
	+ end
	+ )
	+
	+ :ok
	+ end
	+ end
	+ ))
	else
	:ok
	end
	end

	unquote(gen_on_load(env))
	end
	end

	defp gen_on_load(env) do
	case get_on_load_attribute(env.module) do
	nil ->
	quote do
	@on_load :__declare_prometheus_metrics__
	end
	+
	on_load ->
	Module.delete_attribute(env.module, :on_load)
	Module.put_attribute(env.module, :on_load, :__prometheus_on_load_override__)
	+
	quote do
	def __prometheus_on_load_override__() do
	case unquote(on_load)() do
	:ok -> __declare_prometheus_metrics__()
	result -> result
	end
	end
	end
	end
	end

	defp get_on_load_attribute(module) do
	case Module.get_attribute(module, :on_load) do
	[] ->
	nil
	+
	nil ->
	nil
	+
	atom when is_atom(atom) ->
	atom
	+
	{atom, 0} when is_atom(atom) ->
	atom
	+
	[{atom, 0}] when is_atom(atom) ->
	atom
	+
	other ->
	raise ArgumentError,
	- "expected the @on_load attribute to be an atom or a " <>
	- "{atom, 0} tuple, got: #{inspect(other)}"
	+ "expected the @on_load attribute to be an atom or a " <>
	+ "{atom, 0} tuple, got: #{inspect(other)}"
	end
	end

	defp emit_create_metric(:counter, params) do
	quote do
	Prometheus.Metric.Counter.declare(unquote(params))
	end
	end
	+
	defp emit_create_metric(:gauge, params) do
	quote do
	Prometheus.Metric.Gauge.declare(unquote(params))
	end
	end
	+
	defp emit_create_metric(:boolean, params) do
	quote do
	Prometheus.Metric.Boolean.declare(unquote(params))
	end
	end
	+
	defp emit_create_metric(:summary, params) do
	quote do
	Prometheus.Metric.Summary.declare(unquote(params))
	end
	end
	+
	defp emit_create_metric(:histogram, params) do
	quote do
	Prometheus.Metric.Histogram.declare(unquote(params))
	end
	end

	defmacro ct_parsable_spec?(spec) do
	quote do
	is_list(unquote(spec)) or is_atom(unquote(spec))
	end
	end

	def parse_spec(spec) when is_list(spec) do
	registry = Keyword.get(spec, :registry, :default)
	name = Keyword.fetch!(spec, :name)
	labels = Keyword.get(spec, :labels, [])
	{registry, name, labels}
	end
	+
	def parse_spec(spec) when is_atom(spec) do
	{:default, spec, []}
	end
	-
	end
	diff --git a/lib/prometheus/metric/counter.ex b/lib/prometheus/metric/counter.ex
	index 874c550..b524424 100644
	--- a/lib/prometheus/metric/counter.ex
	+++ b/lib/prometheus/metric/counter.ex
	@@ -1,222 +1,223 @@
	defmodule Prometheus.Metric.Counter do
	@moduledoc """
	Counter is a Metric that represents a single numerical value that only ever
	goes up. That implies that it cannot be used to count items whose number can
	also go down, e.g. the number of currently running processes. Those
	"counters" are represented by `Prometheus.Metric.Gauge`.

	A Counter is typically used to count requests served, tasks completed, errors
	occurred, etc.

	Example use cases for Counters:
	- Number of requests processed;
	- Number of items that were inserted into a queue;
	- Total amount of data that a system has processed.

	Use the [`rate()`](https://prometheus.io/docs/querying/functions/#rate())/
	[`irate()`](https://prometheus.io/docs/querying/functions/#irate())
	functions in Prometheus to calculate the rate of increase of a Counter.
	By convention, the names of Counters are suffixed by `_total`.

	To create a counter use either `new/1` or `declare/1`, the difference is that
	`new/` will raise `Prometheus.MFAlreadyExistsError` exception if counter with
	the same `registry`, `name` and `labels` combination already exists.
	Both accept `spec` `Keyword` with the same set of keys:

	- `:registry` - optional, default is `:default`;
	- `:name` - required, can be an atom or a string;
	- `:help` - required, must be a string;
	- `:labels` - optional, default is `[]`.

	Example:

	```
	defmodule MyServiceInstrumenter do

	use Prometheus.Metric

	## to be called at app/supervisor startup.
	## to tolerate restarts use declare.
	def setup() do
	Counter.declare([name: :my_service_requests_total,
	help: "Requests count.",
	labels: [:caller]])
	end

	def inc(caller) do
	Counter.inc([name: :my_service_requests_total,
	labels: [caller]])
	end

	end

	```

	"""

	use Prometheus.Erlang, :prometheus_counter

	@doc """
	Creates a counter using `spec`.

	Raises `Prometheus.MissingMetricSpecKeyError` if required `spec` key is missing.<br>
	Raises `Prometheus.InvalidMetricNameError` if metric name is invalid.<br>
	Raises `Prometheus.InvalidMetricHelpError` if help is invalid.<br>
	Raises `Prometheus.InvalidMetricLabelsError` if labels isn't a list.<br>
	Raises `Prometheus.InvalidLabelNameError` if label name is invalid.<br>
	Raises `Prometheus.MFAlreadyExistsError` if a counter with
	the same `spec` already exists.
	"""
	defmacro new(spec) do
	Erlang.call([spec])
	end

	@doc """
	Creates a counter using `spec`.
	If a counter with the same `spec` exists returns `false`.

	Raises `Prometheus.MissingMetricSpecKeyError` if required `spec` key is missing.<br>
	Raises `Prometheus.InvalidMetricNameError` if metric name is invalid.<br>
	Raises `Prometheus.InvalidMetricHelpError` if help is invalid.<br>
	Raises `Prometheus.InvalidMetricLabelsError` if labels isn't a list.<br>
	Raises `Prometheus.InvalidLabelNameError` if label name is invalid.
	"""
	defmacro declare(spec) do
	Erlang.call([spec])
	end

	@doc """
	Increments the counter identified by `spec` by `value`.

	- Raises `Prometheus.InvalidValueError` exception if `value` isn't a positive integer.<br>
	+ Raises `Prometheus.InvalidValueError` exception if `value` isn't a positive number.<br>
	Raises `Prometheus.UnknownMetricError` exception if a counter
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro inc(spec, value \\ 1) do
	Erlang.metric_call(:inc, spec, [value])
	end

	@doc """
	Increments the counter identified by `spec` by 1 when `body` executed.

	Read more about bodies: `Prometheus.Injector`.

	- Raises `Prometheus.InvalidValueError` exception if `value` isn't a positive integer.<br>
	Raises `Prometheus.UnknownMetricError` exception if a counter
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro count(spec, body) do
	env = __CALLER__
	- Prometheus.Injector.inject(fn(block) ->
	- quote do
	- Prometheus.Metric.Counter.inc(unquote(spec), 1)
	- unquote(block)
	- end
	- end, env, body)
	+
	+ Prometheus.Injector.inject(
	+ fn block ->
	+ quote do
	+ Prometheus.Metric.Counter.inc(unquote(spec), 1)
	+ unquote(block)
	+ end
	+ end,
	+ env,
	+ body
	+ )
	end

	@doc """
	Increments the counter identified by `spec` by 1 when `body` raises `exception`.

	Read more about bodies: `Prometheus.Injector`.

	- Raises `Prometheus.InvalidValueError` exception if `value` isn't a positive integer.<br>
	Raises `Prometheus.UnknownMetricError` exception if a counter
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro count_exceptions(spec, exception \\ :_, body) do
	env = __CALLER__
	- Prometheus.Injector.inject(fn(block) ->
	- quote do
	- require Prometheus.Error
	- Prometheus.Error.with_prometheus_error(
	- try do
	- unquote(block)
	- rescue
	- e in unquote(exception) ->
	- stacktrace = System.stacktrace()
	- {registry, name, labels} = Prometheus.Metric.parse_spec(unquote(spec))
	- :prometheus_counter.inc(registry, name, labels, 1)
	- reraise(e, stacktrace)
	- end)
	- end
	- end, env, body)
	+
	+ Prometheus.Injector.inject(
	+ fn block ->
	+ quote do
	+ require Prometheus.Error
	+
	+ Prometheus.Error.with_prometheus_error(
	+ try do
	+ unquote(block)
	+ rescue
	+ e in unquote(exception) ->
	+ stacktrace = System.stacktrace()
	+ {registry, name, labels} = Prometheus.Metric.parse_spec(unquote(spec))
	+ :prometheus_counter.inc(registry, name, labels, 1)
	+ reraise(e, stacktrace)
	+ end
	+ )
	+ end
	+ end,
	+ env,
	+ body
	+ )
	end

	@doc """
	Increments the counter identified by `spec` by 1 when `body` raises no exceptions.

	Read more about bodies: `Prometheus.Injector`.

	- Raises `Prometheus.InvalidValueError` exception if `value` isn't a positive integer.<br>
	Raises `Prometheus.UnknownMetricError` exception if a counter
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro count_no_exceptions(spec, body) do
	env = __CALLER__
	- Prometheus.Injector.inject(fn(block) ->
	- quote do
	- require Prometheus.Error
	- try do
	- unquote(block)
	- else
	- value ->
	- Prometheus.Metric.Counter.inc(unquote(spec), 1)
	- value
	- end
	- end
	- end, env, body)
	- end

	- @doc """
	- Increments the counter identified by `spec` by `value`.
	- If `value` happened to be a float number even one time(!) you
	- shouldn't use `inc/2` after dinc.
	+ Prometheus.Injector.inject(
	+ fn block ->
	+ quote do
	+ require Prometheus.Error

	- Raises `Prometheus.InvalidValueError` exception if `value` isn't a positive number.<br>
	- Raises `Prometheus.UnknownMetricError` exception if a counter
	- for `spec` can't be found.<br>
	- Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	- """
	- defmacro dinc(spec, value \\ 1) do
	- Erlang.metric_call({:prometheus_counter, :dinc}, spec, [value])
	+ try do
	+ unquote(block)
	+ else
	+ value ->
	+ Prometheus.Metric.Counter.inc(unquote(spec), 1)
	+ value
	+ end
	+ end
	+ end,
	+ env,
	+ body
	+ )
	end

	@doc """
	Removes counter series identified by spec.

	Raises `Prometheus.UnknownMetricError` exception if a counter
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro remove(spec) do
	Erlang.metric_call(spec)
	end

	@doc """
	Resets the value of the counter identified by `spec`.

	Raises `Prometheus.UnknownMetricError` exception if a counter
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro reset(spec) do
	Erlang.metric_call(spec)
	end

	@doc """
	Returns the value of the counter identified by `spec`. If there is no counter for
	given labels combination, returns `:undefined`.

	Raises `Prometheus.UnknownMetricError` exception if a counter
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro value(spec) do
	Erlang.metric_call(spec)
	end
	end
	diff --git a/lib/prometheus/metric/gauge.ex b/lib/prometheus/metric/gauge.ex
	index 1760b53..5da09be 100644
	--- a/lib/prometheus/metric/gauge.ex
	+++ b/lib/prometheus/metric/gauge.ex
	@@ -1,247 +1,231 @@
	defmodule Prometheus.Metric.Gauge do
	@moduledoc """
	Gauge metric, to report instantaneous values.

	Gauge is a metric that represents a single numerical value that can
	arbitrarily go up and down.

	A Gauge is typically used for measured values like temperatures or current
	memory usage, but also "counts" that can go up and down, like the number of
	running processes.

	Example use cases for Gauges:
	- Inprogress requests;
	- Number of items in a queue;
	- Free memory;
	- Total memory;
	- Temperature.

	Example:

	```
	defmodule MyPoolInstrumenter do

	use Prometheus.Metric

	## to be called at app/supervisor startup.
	## to tolerate restarts use declare.
	def setup() do
	Gauge.declare([name: :my_pool_size,
	help: "Pool size."])

	Gauge.declare([name: :my_pool_checked_out,
	help: "Number of sockets checked out from the pool"])
	end

	def set_size(size) do
	Gauge.set([name: :my_pool_size], size)
	end

	def track_checked_out_sockets(checkout_fun) do
	Gauge.track_inprogress([name: :my_pool_checked_out], checkout_fun.())
	end

	def track_checked_out_sockets_block(socket) do
	Gauge.track_inprogress([name: :my_pool_checked_out]) do
	# checkout code
	socket
	end
	end

	end

	```

	"""

	use Prometheus.Erlang, :prometheus_gauge

	@doc """
	Creates a gauge using `spec`.

	Raises `Prometheus.MissingMetricSpecKeyError` if required `spec` key is missing.<br>
	Raises `Prometheus.InvalidMetricNameError` if metric name is invalid.<br>
	Raises `Prometheus.InvalidMetricHelpError` if help is invalid.<br>
	Raises `Prometheus.InvalidMetricLabelsError` if labels isn't a list.<br>
	Raises `Prometheus.InvalidMetricNameError` if label name is invalid.<br>
	Raises `Prometheus.InvalidValueError` exception if duration_unit is unknown or
	doesn't match metric name.<br>
	Raises `Prometheus.MFAlreadyExistsError` if a gauge with the same `spec` exists.
	"""
	defmacro new(spec) do
	Erlang.call([spec])
	end

	@doc """
	Creates a gauge using `spec`.
	If a gauge with the same `spec` exists returns `false`.

	Raises `Prometheus.MissingMetricSpecKeyError` if required `spec` key is missing.<br>
	Raises `Prometheus.InvalidMetricNameError` if metric name is invalid.<br>
	Raises `Prometheus.InvalidMetricHelpError` if help is invalid.<br>
	Raises `Prometheus.InvalidMetricLabelsError` if labels isn't a list.<br>
	Raises `Prometheus.InvalidMetricNameError` if label name is invalid.<br>
	Raises `Prometheus.InvalidValueError` exception if duration_unit is unknown or
	doesn't match metric name.
	"""
	defmacro declare(spec) do
	Erlang.call([spec])
	end

	@doc """
	Sets the gauge identified by `spec` to `value`.

	Raises `Prometheus.InvalidValueError` exception if `value` isn't
	a number or `:undefined`.<br>
	Raises `Prometheus.UnknownMetricError` exception if a gauge for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro set(spec, value) do
	Erlang.metric_call(spec, [value])
	end

	@doc """
	Increments the gauge identified by `spec` by `value`.

	- Raises `Prometheus.InvalidValueError` exception if `value` isn't an integer.<br>
	+ Raises `Prometheus.InvalidValueError` exception if `value` isn't a number.<br>
	Raises `Prometheus.UnknownMetricError` exception if a gauge for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro inc(spec, value \\ 1) do
	Erlang.metric_call(spec, [value])
	end

	@doc """
	Decrements the gauge identified by `spec` by `value`.

	- Raises `Prometheus.InvalidValueError` exception if `value` isn't an integer.<br>
	+ Raises `Prometheus.InvalidValueError` exception if `value` isn't a number.<br>
	Raises `Prometheus.UnknownMetricError` exception if a gauge for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro dec(spec, value \\ 1) do
	Erlang.metric_call(spec, [value])
	end

	- @doc """
	- Increments the gauge identified by `spec` by `value`.
	- If `value` happened to be a float number even one time(!) you shouldn't
	- use `inc/2` or `dec/2` after dinc.
	-
	- Raises `Prometheus.InvalidValueError` exception if `value` isn't a number.<br>
	- Raises `Prometheus.UnknownMetricError` exception if a gauge
	- for `spec` can't be found.<br>
	- Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	- """
	- defmacro dinc(spec, value \\ 1) do
	- Erlang.metric_call(spec, [value])
	- end
	-
	- @doc """
	- Decrements the gauge identified by `spec` by `value`.
	- If `value` happened to be a float number even one time(!) you shouldn't
	- use `inc/2` or `dec/2` after ddec.
	-
	- Raises `Prometheus.InvalidValueError` exception if `value` isn't a number.<br>
	- Raises `Prometheus.UnknownMetricError` exception if a gauge
	- for `spec` can't be found.<br>
	- Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	- """
	- defmacro ddec(spec, value \\ 1) do
	- Erlang.metric_call(spec, [value])
	- end
	-
	@doc """
	Sets the gauge identified by `spec` to the current unixtime.

	Raises `Prometheus.UnknownMetricError` exception if a gauge
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro set_to_current_time(spec) do
	Erlang.metric_call(spec)
	end

	@doc """
	Sets the gauge identified by `spec` to the number of currently executing `body`s.

	Raises `Prometheus.UnknownMetricError` exception if a gauge
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	Raises `Prometheus.InvalidValueError` exception if fun isn't a function or block.
	"""
	defmacro track_inprogress(spec, body) do
	env = __CALLER__
	- Prometheus.Injector.inject(fn(block) ->
	- quote do
	- Prometheus.Metric.Gauge.inc(unquote(spec))
	- try do
	- unquote(block)
	- after
	- Prometheus.Metric.Gauge.dec(unquote(spec))
	+
	+ Prometheus.Injector.inject(
	+ fn block ->
	+ quote do
	+ Prometheus.Metric.Gauge.inc(unquote(spec))
	+
	+ try do
	+ unquote(block)
	+ after
	+ Prometheus.Metric.Gauge.dec(unquote(spec))
	+ end
	end
	- end
	- end, env, body)
	+ end,
	+ env,
	+ body
	+ )
	end

	@doc """
	Tracks the amount of time spent executing `body`.

	Raises `Prometheus.UnknownMetricError` exception if a gauge
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	Raises `Prometheus.InvalidValueError` exception if `fun` isn't a function or block.
	"""
	defmacro set_duration(spec, body) do
	env = __CALLER__
	- Prometheus.Injector.inject(fn(block) ->
	- quote do
	- start_time = :erlang.monotonic_time()
	- try do
	- unquote(block)
	- after
	- end_time = :erlang.monotonic_time()
	- Prometheus.Metric.Gauge.set(unquote(spec), end_time - start_time)
	+
	+ Prometheus.Injector.inject(
	+ fn block ->
	+ quote do
	+ start_time = :erlang.monotonic_time()
	+
	+ try do
	+ unquote(block)
	+ after
	+ end_time = :erlang.monotonic_time()
	+ Prometheus.Metric.Gauge.set(unquote(spec), end_time - start_time)
	+ end
	end
	- end
	- end, env, body)
	+ end,
	+ env,
	+ body
	+ )
	end

	@doc """
	Removes gauge series identified by spec.

	Raises `Prometheus.UnknownMetricError` exception if a gauge
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro remove(spec) do
	Erlang.metric_call(spec)
	end

	@doc """
	Resets the value of the gauge identified by `spec`.

	Raises `Prometheus.UnknownMetricError` exception if a gauge
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro reset(spec) do
	Erlang.metric_call(spec)
	end

	@doc """
	Returns the value of the gauge identified by `spec`.

	If duration unit set, value will be converted to the duration unit.
	[Read more here.](time.html)

	Raises `Prometheus.UnknownMetricError` exception if a gauge
	for `spec` can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro value(spec) do
	Erlang.metric_call(spec)
	end
	end
	diff --git a/lib/prometheus/metric/histogram.ex b/lib/prometheus/metric/histogram.ex
	index 9fbb6c4..dc6fbe1 100644
	--- a/lib/prometheus/metric/histogram.ex
	+++ b/lib/prometheus/metric/histogram.ex
	@@ -1,180 +1,171 @@
	defmodule Prometheus.Metric.Histogram do
	@moduledoc """
	A Histogram tracks the size and number of events in buckets.
	You can use Histograms for aggregatable calculation of quantiles.

	Example use cases for Histograms:
	- Response latency;
	- Request size.

	Histogram expects `buckets` key in a metric spec. Buckets can be:
	- a list of numbers in increasing order;
	- one of the generate specs (shortcuts for `Prometheus.Buckets` macros)
	- :default;
	- {:linear, start, step, count};
	- {:exponential, start, step, count}.

	Example:

	```

	defmodule ExampleInstrumenter do
	use Prometheus.Metric

	## to be called at app/supervisor startup.
	## to tolerate restarts use declare.
	def setup do
	Histogram.new([name: :http_request_duration_milliseconds,
	labels: [:method],
	buckets: [100, 300, 500, 750, 1000],
	help: "Http Request execution time."])
	end

	def instrument(%{time: time, method: method}) do
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [method]],
	time)
	end
	end

	```

	"""

	use Prometheus.Erlang, :prometheus_histogram

	@doc """
	Creates a histogram using `spec`.
	Histogram cannot have a label named "le".

	Raises `Prometheus.MissingMetricSpecKeyError` if required `spec` key is missing.<br>
	Raises `Prometheus.InvalidMetricNameError` if metric name is invalid.<br>
	Raises `Prometheus.InvalidMetricHelpError` if help is invalid.<br>
	Raises `Prometheus.InvalidMetricLabelsError` if labels isn't a list.<br>
	Raises `Prometheus.InvalidMetricNameError` if label name is invalid.<br>
	Raises `Prometheus.InvalidValueError` exception if duration_unit is unknown or
	doesn't match metric name.<br>
	Raises `Prometheus.MFAlreadyExistsError` if a histogram with the same `spec` exists.

	Histogram-specific exceptions:

	Raises `Prometheus.HistogramNoBucketsError` if buckets are missing, not a list,
	empty list or not known buckets spec.<br>
	Raises `Prometheus.HistogramInvalidBucketsError` if buckets aren't
	in increasing order.<br>
	Raises `Prometheus.HistogramInvalidBoundError` if bucket bound isn't a number.
	"""
	defmacro new(spec) do
	Erlang.call([spec])
	end

	@doc """
	Creates a histogram using `spec`.
	Histogram cannot have a label named "le".

	If a histogram with the same `spec` exists returns `false`.

	Raises `Prometheus.MissingMetricSpecKeyError` if required `spec` key is missing.<br>
	Raises `Prometheus.InvalidMetricNameError` if metric name is invalid.<br>
	Raises `Prometheus.InvalidMetricHelpError` if help is invalid.<br>
	Raises `Prometheus.InvalidMetricLabelsError` if labels isn't a list.<br>
	Raises `Prometheus.InvalidMetricNameError` if label name is invalid.<br>
	Raises `Prometheus.InvalidValueError` exception if duration_unit is unknown or
	doesn't match metric name.

	Histogram-specific exceptions:

	Raises `Prometheus.HistogramNoBucketsError` if buckets are missing, not a list,
	empty list or not known buckets spec.<br>
	Raises `Prometheus.HistogramInvalidBucketsError` if buckets aren't
	in increasing order.<br>
	Raises `Prometheus.HistogramInvalidBoundError` if bucket bound isn't a number.
	"""
	defmacro declare(spec) do
	Erlang.call([spec])
	end

	@doc """
	Observes the given amount.

	Raises `Prometheus.InvalidValueError` exception if `amount` isn't
	- a positive integer.<br>
	+ a number.<br>
	Raises `Prometheus.UnknownMetricError` exception if a histogram for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro observe(spec, amount \\ 1) do
	Erlang.metric_call(spec, [amount])
	end

	- @doc """
	- Observes the given amount.
	- If `amount` happened to be a float number even one time(!) you shouldn't
	- use `observe/2` after dobserve.
	-
	- Raises `Prometheus.InvalidValueError` exception if `amount` isn't
	- a positive integer.<br>
	- Raises `Prometheus.UnknownMetricError` exception if a histogram for `spec`
	- can't be found.<br>
	- Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	- """
	- defmacro dobserve(spec, amount \\ 1) do
	- Erlang.metric_call(spec, [amount])
	- end
	-
	@doc """
	Observes the amount of time spent executing `body`.

	Raises `Prometheus.UnknownMetricError` exception if a histogram for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	Raises `Prometheus.InvalidValueError` exception if fun isn't a function or block.
	"""
	defmacro observe_duration(spec, body) do
	env = __CALLER__
	- Prometheus.Injector.inject(fn(block) ->
	- quote do
	- start_time = :erlang.monotonic_time()
	- try do
	- unquote(block)
	- after
	- end_time = :erlang.monotonic_time()
	- Prometheus.Metric.Histogram.observe(unquote(spec), end_time - start_time)
	+
	+ Prometheus.Injector.inject(
	+ fn block ->
	+ quote do
	+ start_time = :erlang.monotonic_time()
	+
	+ try do
	+ unquote(block)
	+ after
	+ end_time = :erlang.monotonic_time()
	+ Prometheus.Metric.Histogram.observe(unquote(spec), end_time - start_time)
	+ end
	end
	- end
	- end, env, body)
	+ end,
	+ env,
	+ body
	+ )
	end

	@doc """
	Removes histogram series identified by spec.

	Raises `Prometheus.UnknownMetricError` exception if a histogram for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro remove(spec) do
	Erlang.metric_call(spec)
	end

	@doc """
	Resets the value of the histogram identified by `spec`.

	Raises `Prometheus.UnknownMetricError` exception if a histogram for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro reset(spec) do
	Erlang.metric_call(spec)
	end

	@doc """
	Returns the value of the histogram identified by `spec`. If there is no histogram for
	given labels combination, returns `:undefined`.

	Raises `Prometheus.UnknownMetricError` exception if a histogram for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro value(spec) do
	Erlang.metric_call(spec)
	end
	end
	diff --git a/lib/prometheus/metric/summary.ex b/lib/prometheus/metric/summary.ex
	index 87957c0..0aa082a 100644
	--- a/lib/prometheus/metric/summary.ex
	+++ b/lib/prometheus/metric/summary.ex
	@@ -1,162 +1,154 @@
	defmodule Prometheus.Metric.Summary do
	@moduledoc """
	Summary metric, to track the size of events.

	Example use cases for Summaries:
	- Response latency;
	- Request size;
	- Response size.

	Example:

	```
	defmodule MyProxyInstrumenter do

	use Prometheus.Metric

	## to be called at app/supervisor startup.
	## to tolerate restarts use declare.
	def setup() do
	Summary.declare([name: :request_size_bytes,
	help: "Request size in bytes."])

	Summary.declare([name: :response_size_bytes,
	help: "Response size in bytes."])
	end

	def observe_request(size) do
	Summary.observe([name: :request_size_bytes], size)
	end

	def observe_response(size) do
	Summary.observe([name: :response_size_bytes], size)
	end
	end
	```

	"""

	use Prometheus.Erlang, :prometheus_summary

	@doc """
	Creates a summary using `spec`.
	Summary cannot have a label named "quantile".

	Raises `Prometheus.MissingMetricSpecKeyError` if required `spec` key is missing.<br>
	Raises `Prometheus.InvalidMetricNameError` if metric name is invalid.<br>
	Raises `Prometheus.InvalidMetricHelpError` if help is invalid.<br>
	Raises `Prometheus.InvalidMetricLabelsError` if labels isn't a list.<br>
	Raises `Prometheus.InvalidMetricNameError` if label name is invalid.<br>
	Raises `Prometheus.InvalidValueError` exception if duration_unit is unknown or
	doesn't match metric name.<br>
	Raises `Prometheus.MFAlreadyExistsError` if a summary with the same `spec`
	already exists.
	"""
	defmacro new(spec) do
	Erlang.call([spec])
	end

	@doc """
	Creates a summary using `spec`.
	Summary cannot have a label named "quantile".

	If a summary with the same `spec` exists returns `false`.

	Raises `Prometheus.MissingMetricSpecKeyError` if required `spec` key is missing.<br>
	Raises `Prometheus.InvalidMetricNameError` if metric name is invalid.<br>
	Raises `Prometheus.InvalidMetricHelpError` if help is invalid.<br>
	Raises `Prometheus.InvalidMetricLabelsError` if labels isn't a list.<br>
	Raises `Prometheus.InvalidMetricNameError` if label name is invalid;<br>
	Raises `Prometheus.InvalidValueError` exception if duration_unit is unknown or
	doesn't match metric name.
	"""
	defmacro declare(spec) do
	Erlang.call([spec])
	end

	@doc """
	Observes the given amount.

	- Raises `Prometheus.InvalidValueError` exception if `amount` isn't an integer.<br>
	- Raises `Prometheus.UnknownMetricError` exception if a summary for `spec`
	- can't be found.<br>
	- Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	- """
	- defmacro observe(spec, amount \\ 1) do
	- Erlang.metric_call(spec, [amount])
	- end
	-
	- @doc """
	- Observes the given amount.
	- If `amount` happened to be a float number even one time(!) you shouldn't use `observe/2`
	- after dobserve.
	-
	Raises `Prometheus.InvalidValueError` exception if `amount` isn't a number.<br>
	Raises `Prometheus.UnknownMetricError` exception if a summary for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	- defmacro dobserve(spec, amount \\ 1) do
	+ defmacro observe(spec, amount \\ 1) do
	Erlang.metric_call(spec, [amount])
	end

	@doc """
	Observes the amount of time spent executing `body`.

	Raises `Prometheus.UnknownMetricError` exception if a summary for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	Raises `Prometheus.InvalidValueError` exception if `fun` isn't a function or block.
	"""
	defmacro observe_duration(spec, body) do
	env = __CALLER__
	- Prometheus.Injector.inject(fn(block) ->
	- quote do
	- start_time = :erlang.monotonic_time()
	- try do
	- unquote(block)
	- after
	- end_time = :erlang.monotonic_time()
	- Prometheus.Metric.Summary.observe(unquote(spec), end_time - start_time)
	+
	+ Prometheus.Injector.inject(
	+ fn block ->
	+ quote do
	+ start_time = :erlang.monotonic_time()
	+
	+ try do
	+ unquote(block)
	+ after
	+ end_time = :erlang.monotonic_time()
	+ Prometheus.Metric.Summary.observe(unquote(spec), end_time - start_time)
	+ end
	end
	- end
	- end, env, body)
	+ end,
	+ env,
	+ body
	+ )
	end

	@doc """
	Removes summary series identified by spec.

	Raises `Prometheus.UnknownMetricError` exception if a summary for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro remove(spec) do
	Erlang.metric_call(spec)
	end

	@doc """
	Resets the value of the summary identified by `spec`.

	Raises `Prometheus.UnknownMetricError` exception if a summary for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro reset(spec) do
	Erlang.metric_call(spec)
	end

	@doc """
	Returns the value of the summary identified by `spec`. If there is no summary for
	given labels combination, returns `:undefined`.

	If duration unit set, sum will be converted to the duration unit.
	[Read more here.](time.html)

	Raises `Prometheus.UnknownMetricError` exception if a summary for `spec`
	can't be found.<br>
	Raises `Prometheus.InvalidMetricArityError` exception if labels count mismatch.
	"""
	defmacro value(spec) do
	Erlang.metric_call(spec)
	end
	end
	diff --git a/lib/prometheus/model.ex b/lib/prometheus/model.ex
	index 75637ea..cf6e3e0 100644
	--- a/lib/prometheus/model.ex
	+++ b/lib/prometheus/model.ex
	@@ -1,151 +1,150 @@
	defmodule Prometheus.Model do
	@moduledoc """
	Helpers for working with Prometheus data model. For advanced users.

	`Prometheus.Collector` example demonstrates how to use this module.
	"""

	use Prometheus.Erlang, :prometheus_model_helpers

	@doc """
	Creates Metric Family of `type`, `name` and `help`.
	`collector.collect_metrics/2` callback will be called and expected to
	return individual metrics list.
	"""
	defmacro create_mf(name, help, type, collector, collector_data) do
	Erlang.call([name, help, type, collector, collector_data])
	end

	@doc """
	Creates gauge metrics from `mdata` {label, value} tuple list.

	iex(11)> Prometheus.Model.gauge_metrics([{[host: "example.com"], 100}])
	[{:Metric, [{:LabelPair, "host", "example.com"}], {:Gauge, 100}, :undefined,
	:undefined, :undefined, :undefined, :undefined}]

	"""
	defmacro gauge_metrics(mdata) do
	Erlang.call([mdata])
	end

	@doc """
	Creates gauge metric with `labels` and `value`.

	iex(13)> Prometheus.Model.gauge_metric([host: "example.com"], 100)
	{:Metric, [{:LabelPair, "host", "example.com"}], {:Gauge, 100}, :undefined,
	:undefined, :undefined, :undefined, :undefined}

	"""
	defmacro gauge_metric(labels \\ [], value) do
	Erlang.call([labels, value])
	end

	@doc """
	Creates untyped metrics from `mdata` {label, value} tuple list.

	iex(11)> Prometheus.Model.untyped_metrics([{[host: "example.com"], 100}])
	[{:Metric, [{:LabelPair, "host", "example.com"}], :undefined,
	:undefined, :undefined, {:Untyped, 100}, :undefined, :undefined}]

	"""
	defmacro untyped_metrics(mdata) do
	Erlang.call([mdata])
	end

	@doc """
	Creates untyped metric with `labels` and `value`.

	iex(13)> Prometheus.Model.untyped_metric([host: "example.com"], 100)
	{:Metric, [{:LabelPair, "host", "example.com"}], :undefined,
	:undefined, :undefined, {:Untyped, 100}, :undefined, :undefined}

	"""
	defmacro untyped_metric(labels \\ [], value) do
	Erlang.call([labels, value])
	end

	@doc """
	Creates counter metrics from `mdata` {labels, value} tuple list.

	iex(14)> Prometheus.Model.counter_metrics([{[host: "example.com"], 100}])
	[{:Metric, [{:LabelPair, "host", "example.com"}], :undefined, {:Counter, 100},
	:undefined, :undefined, :undefined, :undefined}]

	"""
	defmacro counter_metrics(mdata) do
	Erlang.call([mdata])
	end

	@doc """
	Creates counter metric with `labels` and `value`.

	iex(15)> Prometheus.Model.counter_metric([host: "example.com"], 100)
	{:Metric, [{:LabelPair, "host", "example.com"}], :undefined, {:Counter, 100},
	:undefined, :undefined, :undefined, :undefined}

	"""
	defmacro counter_metric(labels \\ [], value) do
	Erlang.call([labels, value])
	end

	@doc """
	Creates summary metrics from `mdata` {labels, count, sum} tuple list.

	iex(7)> Prometheus.Model.summary_metrics([{[{:method, :get}], 2, 10.5}])
	[{:Metric, [{:LabelPair, "method", "get"}], :undefined, :undefined,
	{:Summary, 2, 10.5, []}, :undefined, :undefined, :undefined}]

	"""
	defmacro summary_metrics(mdata) do
	Erlang.call([mdata])
	end

	@doc """
	Creates summary metric with `labels`, `count`, and `sum`.

	iex(3)> Prometheus.Model.summary_metric([{:method, :get}], 2, 10.5)
	{:Metric, [{:LabelPair, "method", "get"}], :undefined, :undefined,
	{:Summary, 2, 10.5, []}, :undefined, :undefined, :undefined}

	"""
	defmacro summary_metric(labels \\ [], count, sum) do
	Erlang.call([labels, count, sum])
	end

	@doc """
	Creates histogram metrics from `mdata` {labels, buckets, count, sum} tuple list.

	iex(2)> Prometheus.Model.histogram_metrics([{[{:method, :get}],
	...(2)> [{2, 1}, {5, 1}, {:infinity, 2}],
	...(2)> 2, 10.5}])
	[{:Metric, [{:LabelPair, "method", "get"}], :undefined, :undefined, :undefined,
	:undefined,
	{:Histogram, 2, 10.5,
	[{:Bucket, 1, 2}, {:Bucket, 1, 5}, {:Bucket, 2, :infinity}]}, :undefined}]

	"""
	defmacro histogram_metrics(mdata) do
	Erlang.call([mdata])
	end

	@doc """
	Creates histogram metric with `labels`, `buckets`, `count`, and `sum`.

	iex(4)> Prometheus.Model.histogram_metric([{:method, :get}],
	...(4)> [{2, 1}, {5, 1}, {:infinity, 2}],
	...(4)> 2, 10.5)
	{:Metric, [{:LabelPair, "method", "get"}], :undefined, :undefined, :undefined,
	:undefined,
	{:Histogram, 2, 10.5,
	[{:Bucket, 1, 2}, {:Bucket, 1, 5}, {:Bucket, 2, :infinity}]}, :undefined}

	Buckets is a list of pairs {upper_bound, cumulative_count}.
	Cumulative count is a sum of all cumulative_counts of previous buckets + counter of
	current bucket.

	"""
	defmacro histogram_metric(labels \\ [], buckets, count, sum) do
	Erlang.call([labels, buckets, count, sum])
	end
	-
	end
	diff --git a/lib/prometheus/registry.ex b/lib/prometheus/registry.ex
	index 4f1dadb..b81a1a6 100644
	--- a/lib/prometheus/registry.ex
	+++ b/lib/prometheus/registry.ex
	@@ -1,74 +1,73 @@
	defmodule Prometheus.Registry do
	@moduledoc """
	A registry of Collectors.

	The majority of users should use the `:default`, rather than their own.

	Creating a registry other than the default is primarily useful for
	unit tests, or pushing a subset of metrics to the
	[Pushgateway](https://github.com/prometheus/pushgateway) from batch jobs.
	"""

	use Prometheus.Erlang, :prometheus_registry

	@doc """
	Tries to find registry with the `name`.
	Assumes that registry name is always an atom.
	If `Name` is an atom `ets:lookup/2` is used
	If `Name` is an iolist performs safe search (to avoid interning
	atoms) and returns atom or false. This operation is O(n).
	"""
	defmacro exists(name) do
	Erlang.call([name])
	end

	@doc """
	Calls `callback` for each collector with two arguments: `registry` and `collector`.
	"""
	defmacro collect(callback, registry \\ :default) do
	Erlang.call([registry, callback])
	end

	@doc """
	Returns collectors registered in `registry`.
	"""
	defmacro collectors(registry \\ :default) do
	Erlang.call([registry])
	end

	@doc """
	Registers a collector.
	"""
	defmacro register_collector(registry \\ :default, collector) do
	Erlang.call([registry, collector])
	end

	@doc """
	Registers collectors list.
	"""
	defmacro register_collectors(registry \\ :default, collectors) do
	Erlang.call([registry, collectors])
	end

	@doc """
	Unregisters a collector.
	"""
	defmacro deregister_collector(registry \\ :default, collector) do
	Erlang.call([registry, collector])
	end

	@doc """
	Unregisters all collectors.
	"""
	defmacro clear(registry \\ :default) do
	Erlang.call([registry])
	end

	@doc """
	Checks whether `collector` is registered.
	"""
	defmacro collector_registered?(registry \\ :default, collector) do
	Erlang.call(:collector_registeredp, [registry, collector])
	end
	-
	end
	diff --git a/mix.exs b/mix.exs
	index 4e99166..1d9e12d 100644
	--- a/mix.exs
	+++ b/mix.exs
	@@ -1,58 +1,72 @@
	defmodule PrometheusEx.Mixfile do
	use Mix.Project

	@version "2.0.0"

	def project do
	- [app: :prometheus_ex,
	- version: @version,
	- elixir: "~> 1.3",
	- build_embedded: Mix.env == :prod,
	- start_permanent: Mix.env == :prod,
	- description: description(),
	- package: package(),
	- name: "Prometheus.ex",
	- deps: deps(),
	- test_coverage: [tool: ExCoveralls],
	- preferred_cli_env: ["coveralls": :test, "coveralls.html": :test],
	- docs: [main: Prometheus,
	- source_ref: "v#{@version}",
	- source_url: "https://github.com/deadtrickster/prometheus.ex",
	- extras: ["pages/Mnesia Collector.md",
	- "pages/VM Memory Collector.md",
	- "pages/VM Statistics Collector.md",
	- "pages/VM System Info Collector.md",
	- "pages/Time.md"]]]
	+ [
	+ app: :prometheus_ex,
	+ version: @version,
	+ elixir: "~> 1.6",
	+ build_embedded: Mix.env() == :prod,
	+ start_permanent: Mix.env() == :prod,
	+ description: description(),
	+ package: package(),
	+ name: "Prometheus.ex",
	+ deps: deps(),
	+ test_coverage: [tool: ExCoveralls],
	+ preferred_cli_env: [coveralls: :test, "coveralls.html": :test],
	+ docs: [
	+ main: Prometheus,
	+ source_ref: "v#{@version}",
	+ source_url: "https://github.com/deadtrickster/prometheus.ex",
	+ extras: [
	+ "pages/Mnesia Collector.md",
	+ "pages/VM Memory Collector.md",
	+ "pages/VM Statistics Collector.md",
	+ "pages/VM System Info Collector.md",
	+ "pages/Time.md"
	+ ]
	+ ]
	+ ]
	end

	def application do
	- [applications: [:logger,
	- :prometheus]]
	+ [applications: [:logger, :prometheus]]
	end

	defp description do
	"""
	Elixir-friendly Prometheus monitoring system client.
	"""
	end

	defp package do
	- [maintainers: ["Ilya Khaprov"],
	- licenses: ["MIT"],
	- links: %{"GitHub" => "https://github.com/deadtrickster/prometheus.ex",
	- "Prometheus.erl" => "https://hex.pm/packages/prometheus",
	- "Inets HTTPD Exporter" => "https://hex.pm/packages/prometheus_httpd",
	- "Ecto Instrumenter" => "https://hex.pm/packages/prometheus_ecto",
	- "Phoenix Instrumenter" => "https://hex.pm/packages/prometheus_phoenix",
	- "Plugs Instrumenter/Exporter" => "https://hex.pm/packages/prometheus_plugs",
	- "Process info Collector" => "https://hex.pm/packages/prometheus_process_collector"}]
	+ [
	+ maintainers: ["Ilya Khaprov"],
	+ licenses: ["MIT"],
	+ links: %{
	+ "GitHub" => "https://github.com/deadtrickster/prometheus.ex",
	+ "Prometheus.erl" => "https://hex.pm/packages/prometheus",
	+ "Inets HTTPD Exporter" => "https://hex.pm/packages/prometheus_httpd",
	+ "Ecto Instrumenter" => "https://hex.pm/packages/prometheus_ecto",
	+ "Phoenix Instrumenter" => "https://hex.pm/packages/prometheus_phoenix",
	+ "Plugs Instrumenter/Exporter" => "https://hex.pm/packages/prometheus_plugs",
	+ "Process info Collector" => "https://hex.pm/packages/prometheus_process_collector"
	+ }
	+ ]
	end

	defp deps do
	- [{:prometheus, "~> 3.4"},
	- {:credo, "~> 0.8", only: :test},
	- {:excoveralls, "~> 0.7", only: :test},
	- {:ex_doc, "~> 0.11", only: :dev},
	- {:earmark, ">= 0.0.0", only: :dev}]
	+ [
	+ {:prometheus, "~> 4.0"},
	+
	+ ## test
	+ {:credo, "~> 0.8", only: [:dev, :test]},
	+ {:dialyxir, "~> 0.5", only: [:dev]},
	+ {:earmark, "~> 1.2", only: [:dev]},
	+ {:ex_doc, "~> 0.18", only: [:dev]},
	+ {:excoveralls, "~> 0.8", only: [:test]},
	+ ]
	end
	end
	diff --git a/mix.lock b/mix.lock
	index 5df2510..3f2e1d6 100644
	--- a/mix.lock
	+++ b/mix.lock
	@@ -1,15 +1,18 @@
	-%{"bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], []},
	- "certifi": {:hex, :certifi, "2.0.0", "a0c0e475107135f76b8c1d5bc7efb33cd3815cb3cf3dea7aefdd174dabead064", [:rebar3], []},
	- "credo": {:hex, :credo, "0.8.6", "335f723772d35da499b5ebfdaf6b426bfb73590b6fcbc8908d476b75f8cbca3f", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, optional: false]}]},
	- "earmark": {:hex, :earmark, "1.2.3", "206eb2e2ac1a794aa5256f3982de7a76bf4579ff91cb28d0e17ea2c9491e46a4", [:mix], []},
	- "ex_doc": {:hex, :ex_doc, "0.16.2", "3b3e210ebcd85a7c76b4e73f85c5640c011d2a0b2f06dcdf5acdb2ae904e5084", [:mix], [{:earmark, "~> 1.1", [hex: :earmark, optional: false]}]},
	- "excoveralls": {:hex, :excoveralls, "0.7.2", "f69ede8c122ccd3b60afc775348a53fc8c39fe4278aee2f538f0d81cc5e7ff3a", [:mix], [{:exjsx, ">= 3.0.0", [hex: :exjsx, optional: false]}, {:hackney, ">= 0.12.0", [hex: :hackney, optional: false]}]},
	- "exjsx": {:hex, :exjsx, "4.0.0", "60548841e0212df401e38e63c0078ec57b33e7ea49b032c796ccad8cde794b5c", [:mix], [{:jsx, "~> 2.8.0", [hex: :jsx, optional: false]}]},
	- "hackney": {:hex, :hackney, "1.9.0", "51c506afc0a365868469dcfc79a9d0b94d896ec741cfd5bd338f49a5ec515bfe", [:rebar3], [{:certifi, "2.0.0", [hex: :certifi, optional: false]}, {:idna, "5.1.0", [hex: :idna, optional: false]}, {:metrics, "1.0.1", [hex: :metrics, optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, optional: false]}, {:ssl_verify_fun, "1.1.1", [hex: :ssl_verify_fun, optional: false]}]},
	- "idna": {:hex, :idna, "5.1.0", "d72b4effeb324ad5da3cab1767cb16b17939004e789d8c0ad5b70f3cea20c89a", [:rebar3], [{:unicode_util_compat, "0.3.1", [hex: :unicode_util_compat, optional: false]}]},
	- "jsx": {:hex, :jsx, "2.8.2", "7acc7d785b5abe8a6e9adbde926a24e481f29956dd8b4df49e3e4e7bcc92a018", [:mix, :rebar3], []},
	- "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [], []},
	- "mimerl": {:hex, :mimerl, "1.0.2", "993f9b0e084083405ed8252b99460c4f0563e41729ab42d9074fd5e52439be88", [], []},
	- "prometheus": {:hex, :prometheus, "3.4.0", "91759726f2e384df2ef48daf039d506705a7aa81dcbbb2dbffee1fd0c5431d32", [:mix, :rebar3], []},
	- "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.1", "28a4d65b7f59893bc2c7de786dec1e1555bd742d336043fe644ae956c3497fbe", [:make, :rebar], []},
	- "unicode_util_compat": {:hex, :unicode_util_compat, "0.3.1", "a1f612a7b512638634a603c8f401892afbf99b8ce93a45041f8aaca99cadb85e", [:rebar3], []}}
	+%{
	+ "bunt": {:hex, :bunt, "0.2.0", "951c6e801e8b1d2cbe58ebbd3e616a869061ddadcc4863d0a2182541acae9a38", [:mix], [], "hexpm"},
	+ "certifi": {:hex, :certifi, "2.0.0", "a0c0e475107135f76b8c1d5bc7efb33cd3815cb3cf3dea7aefdd174dabead064", [:rebar3], [], "hexpm"},
	+ "credo": {:hex, :credo, "0.8.10", "261862bb7363247762e1063713bb85df2bbd84af8d8610d1272cd9c1943bba63", [:mix], [{:bunt, "~> 0.2.0", [hex: :bunt, repo: "hexpm", optional: false]}], "hexpm"},
	+ "dialyxir": {:hex, :dialyxir, "0.5.1", "b331b091720fd93e878137add264bac4f644e1ddae07a70bf7062c7862c4b952", [:mix], [], "hexpm"},
	+ "earmark": {:hex, :earmark, "1.2.4", "99b637c62a4d65a20a9fb674b8cffb8baa771c04605a80c911c4418c69b75439", [:mix], [], "hexpm"},
	+ "ex_doc": {:hex, :ex_doc, "0.18.3", "f4b0e4a2ec6f333dccf761838a4b253d75e11f714b85ae271c9ae361367897b7", [:mix], [{:earmark, "~> 1.1", [hex: :earmark, repo: "hexpm", optional: false]}], "hexpm"},
	+ "excoveralls": {:hex, :excoveralls, "0.8.1", "0bbf67f22c7dbf7503981d21a5eef5db8bbc3cb86e70d3798e8c802c74fa5e27", [:mix], [{:exjsx, ">= 3.0.0", [hex: :exjsx, repo: "hexpm", optional: false]}, {:hackney, ">= 0.12.0", [hex: :hackney, repo: "hexpm", optional: false]}], "hexpm"},
	+ "exjsx": {:hex, :exjsx, "4.0.0", "60548841e0212df401e38e63c0078ec57b33e7ea49b032c796ccad8cde794b5c", [:mix], [{:jsx, "~> 2.8.0", [hex: :jsx, repo: "hexpm", optional: false]}], "hexpm"},
	+ "hackney": {:hex, :hackney, "1.11.0", "4951ee019df102492dabba66a09e305f61919a8a183a7860236c0fde586134b6", [:rebar3], [{:certifi, "2.0.0", [hex: :certifi, repo: "hexpm", optional: false]}, {:idna, "5.1.0", [hex: :idna, repo: "hexpm", optional: false]}, {:metrics, "1.0.1", [hex: :metrics, repo: "hexpm", optional: false]}, {:mimerl, "1.0.2", [hex: :mimerl, repo: "hexpm", optional: false]}, {:ssl_verify_fun, "1.1.1", [hex: :ssl_verify_fun, repo: "hexpm", optional: false]}], "hexpm"},
	+ "idna": {:hex, :idna, "5.1.0", "d72b4effeb324ad5da3cab1767cb16b17939004e789d8c0ad5b70f3cea20c89a", [:rebar3], [{:unicode_util_compat, "0.3.1", [hex: :unicode_util_compat, repo: "hexpm", optional: false]}], "hexpm"},
	+ "jsx": {:hex, :jsx, "2.8.3", "a05252d381885240744d955fbe3cf810504eb2567164824e19303ea59eef62cf", [:mix, :rebar3], [], "hexpm"},
	+ "metrics": {:hex, :metrics, "1.0.1", "25f094dea2cda98213cecc3aeff09e940299d950904393b2a29d191c346a8486", [], [], "hexpm"},
	+ "mimerl": {:hex, :mimerl, "1.0.2", "993f9b0e084083405ed8252b99460c4f0563e41729ab42d9074fd5e52439be88", [], [], "hexpm"},
	+ "prometheus": {:hex, :prometheus, "4.1.0", "3bb851df031c204d1c94bf55fff2ecc9ab834f0236e64c080c9d5945b48d428d", [:mix, :rebar3], [], "hexpm"},
	+ "ssl_verify_fun": {:hex, :ssl_verify_fun, "1.1.1", "28a4d65b7f59893bc2c7de786dec1e1555bd742d336043fe644ae956c3497fbe", [:make, :rebar], [], "hexpm"},
	+ "unicode_util_compat": {:hex, :unicode_util_compat, "0.3.1", "a1f612a7b512638634a603c8f401892afbf99b8ce93a45041f8aaca99cadb85e", [:rebar3], [], "hexpm"},
	+}
	diff --git a/test/buckets_test.exs b/test/buckets_test.exs
	index 656bf25..4e0f37a 100644
	--- a/test/buckets_test.exs
	+++ b/test/buckets_test.exs
	@@ -1,34 +1,38 @@
	defmodule Prometheus.BucketsTest do
	use ExUnit.Case

	use Prometheus

	doctest Prometheus.Buckets

	test "linear buckets generator tests" do
	assert_raise Prometheus.InvalidValueError, fn ->
	- Prometheus.Buckets.linear(-15, 5, 0)
	+ Prometheus.Buckets.new({:linear, -15, 5, 0})
	end

	- assert [-15, -10, -5, 0, 5, 10] == Prometheus.Buckets.linear(-15, 5, 6)
	+ assert [-15, -10, -5, 0, 5, 10, :infinity] ==
	+ Prometheus.Buckets.new({:linear, -15, 5, 6})
	end

	test "exponential buckets generator tests" do
	assert_raise Prometheus.InvalidValueError, fn ->
	- Prometheus.Buckets.exponential(-15, 5, 0)
	+ Prometheus.Buckets.new({:exponential, -15, 5, 0})
	end
	+
	assert_raise Prometheus.InvalidValueError, fn ->
	- Prometheus.Buckets.exponential(-15, 5, 2)
	+ Prometheus.Buckets.new({:exponential, -15, 5, 2})
	end
	+
	assert_raise Prometheus.InvalidValueError, fn ->
	- Prometheus.Buckets.exponential(15, 0.5, 3)
	+ Prometheus.Buckets.new({:exponential, 15, 0.5, 3})
	end

	- assert [100, 120, 144] == Prometheus.Buckets.exponential(100, 1.2, 3)
	+ assert [100, 120, 144, :infinity] ==
	+ Prometheus.Buckets.new({:exponential, 100, 1.2, 3})
	end

	test "default buckets test" do
	- assert [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10] ==
	- Prometheus.Buckets.default
	+ assert [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10, :infinity] ==
	+ Prometheus.Buckets.new(:default)
	end
	end
	diff --git a/test/collector_test.exs b/test/collector_test.exs
	index ca440cf..6ce9c10 100644
	--- a/test/collector_test.exs
	+++ b/test/collector_test.exs
	@@ -1,44 +1,47 @@
	defmodule Prometheus.CollectorTest do
	-
	use Prometheus.Case

	import ExUnit.CaptureIO

	def deregister_cleanup(_), do: :ok

	test "Collector tests" do
	## test collecting metrics from collector in default registry
	- Counter.declare([name: :test_counter,
	- help: "qwe_qwe"])
	+ Counter.declare(
	+ name: :test_counter,
	+ help: "qwe_qwe"
	+ )

	- Counter.inc([name: :test_counter])
	+ Counter.inc(name: :test_counter)

	assert capture_io(fn ->
	- Prometheus.Collector.collect_mf(:prometheus_counter, fn(mf) ->
	- :io.format("~p", [mf])
	- end)
	- end) ==
	-"{'MetricFamily',<<\"test_counter\">>,\"qwe_qwe\",'COUNTER',
	+ Prometheus.Collector.collect_mf(:prometheus_counter, fn mf ->
	+ :io.format("~p", [mf])
	+ end)
	+ end) == "{'MetricFamily',<<\"test_counter\">>,\"qwe_qwe\",'COUNTER',
	[{'Metric',[],undefined,
	{'Counter',1},
	undefined,undefined,undefined,undefined}]}"

	## test collecting metrics from collector in custom registry
	- Counter.declare([name: :test_counter_qwe,
	- help: "qwe_qwe",
	- registry: :qwe])
	+ Counter.declare(
	+ name: :test_counter_qwe,
	+ help: "qwe_qwe",
	+ registry: :qwe
	+ )

	- Counter.inc([name: :test_counter_qwe,
	- registry: :qwe])
	+ Counter.inc(
	+ name: :test_counter_qwe,
	+ registry: :qwe
	+ )

	assert capture_io(fn ->
	- Prometheus.Collector.collect_mf(:qwe, :prometheus_counter, fn(mf) ->
	- :io.format("~p", [mf])
	- end)
	- end) ==
	-"{'MetricFamily',<<\"test_counter_qwe\">>,\"qwe_qwe\",'COUNTER',
	+ Prometheus.Collector.collect_mf(:qwe, :prometheus_counter, fn mf ->
	+ :io.format("~p", [mf])
	+ end)
	+ end) == "{'MetricFamily',<<\"test_counter_qwe\">>,\"qwe_qwe\",'COUNTER',
	[{'Metric',[],undefined,
	{'Counter',1},
	undefined,undefined,undefined,undefined}]}"
	end
	end
	diff --git a/test/contrib/http_test.exs b/test/contrib/http_test.exs
	index fdcb7b0..3b34371 100644
	--- a/test/contrib/http_test.exs
	+++ b/test/contrib/http_test.exs
	@@ -1,24 +1,41 @@
	defmodule Prometheus.Contrib.HTTPTest do
	use ExUnit.Case
	## alias Prometheus.Error %% FIXME: status_class should throw invalid_value.
	use Prometheus

	doctest Prometheus.Contrib.HTTP

	test "microseconds_duration_buckets" do
	- assert [10, 25, 50, 100, 250, 500, 1_000, 2_500, 5_000, 10_000, 25_000, 50_000,
	- 100_000, 250_000, 500_000, 1_000_000, 2_500_000, 5_000_000, 10_000_000] ==
	- Prometheus.Contrib.HTTP.microseconds_duration_buckets
	+ assert [
	+ 10,
	+ 25,
	+ 50,
	+ 100,
	+ 250,
	+ 500,
	+ 1_000,
	+ 2_500,
	+ 5_000,
	+ 10_000,
	+ 25_000,
	+ 50_000,
	+ 100_000,
	+ 250_000,
	+ 500_000,
	+ 1_000_000,
	+ 2_500_000,
	+ 5_000_000,
	+ 10_000_000
	+ ] == Prometheus.Contrib.HTTP.microseconds_duration_buckets()
	end

	test "status_class" do
	assert 'unknown' == Prometheus.Contrib.HTTP.status_class(50)
	assert 'informational' == Prometheus.Contrib.HTTP.status_class(150)
	assert 'success' == Prometheus.Contrib.HTTP.status_class(250)
	assert 'redirection' == Prometheus.Contrib.HTTP.status_class(350)
	assert 'client-error' == Prometheus.Contrib.HTTP.status_class(450)
	assert 'server-error' == Prometheus.Contrib.HTTP.status_class(550)
	assert 'unknown' == Prometheus.Contrib.HTTP.status_class(650)
	end
	-
	end
	diff --git a/test/contrib/mnesia_test.exs b/test/contrib/mnesia_test.exs
	index 4ba8123..374fd51 100644
	--- a/test/contrib/mnesia_test.exs
	+++ b/test/contrib/mnesia_test.exs
	@@ -1,34 +1,33 @@
	defmodule Prometheus.Contrib.MnesiaTest do
	use ExUnit.Case

	use Prometheus

	test "table disk size" do
	{:ok, root} = :file.get_cwd()
	mnesia_dir = root ++ '/test/mnesia'
	set_custom_mnesia_dir(mnesia_dir)

	assert mnesia_dir == :mnesia.system_info(:directory)

	assert 3 = Prometheus.Contrib.Mnesia.table_disk_size(mnesia_dir, :table)
	assert 21 = Prometheus.Contrib.Mnesia.table_disk_size(:my_table)
	end

	test "tm info test" do
	try do
	:mnesia.start()
	assert {_, _} = Prometheus.Contrib.Mnesia.tm_info()
	after
	:mnesia.stop()
	end
	end

	defp set_custom_mnesia_dir(dir) do
	:ets.lookup_element(:mnesia_gvar, :dir, 2)
	:ets.update_element(:mnesia_gvar, :dir, dir)
	rescue
	ArgumentError ->
	:application.set_env(:mnesia, :dir, dir)
	end
	-
	end
	diff --git a/test/error_test.exs b/test/error_test.exs
	index 32951e5..e3a7d84 100644
	--- a/test/error_test.exs
	+++ b/test/error_test.exs
	@@ -1,21 +1,18 @@
	defmodule Prometheus.ErrorTest do
	-
	use Prometheus.Case
	require Prometheus.Error

	def erlang_error do
	raise ErlangError
	end

	test "properly proxies unknown exceptions" do
	- assert_raise ArgumentError,
	- fn ->
	- Prometheus.Error.with_prometheus_error :ets.tab2list(:qweqweqwe)
	+ assert_raise ArgumentError, fn ->
	+ Prometheus.Error.with_prometheus_error(:ets.tab2list(:qweqweqwe))
	end

	- assert_raise ErlangError,
	- fn ->
	- Prometheus.Error.with_prometheus_error erlang_error()
	+ assert_raise ErlangError, fn ->
	+ Prometheus.Error.with_prometheus_error(erlang_error())
	end
	end
	end
	diff --git a/test/format/protobuf_test.exs b/test/format/protobuf_test.exs
	index 32b6928..2c678e1 100644
	--- a/test/format/protobuf_test.exs
	+++ b/test/format/protobuf_test.exs
	@@ -1,126 +1,149 @@
	# credo:disable-for-this-file Credo.Check.Readability.SpaceAfterCommas
	defmodule Prometheus.Format.ProtobufTest do
	use Prometheus.Case

	require Prometheus.Format.Protobuf

	test "content_type" do
	assert "application/vnd.google.protobuf; " <>
	- "proto=io.prometheus.client.MetricFamily; " <>
	- "encoding=delimited" == Prometheus.Format.Protobuf.content_type
	+ "proto=io.prometheus.client.MetricFamily; " <> "encoding=delimited" ==
	+ Prometheus.Format.Protobuf.content_type()
	end

	test "gauge" do
	- Gauge.new([name: :pool_size, help: "MongoDB Connections pool size"])
	+ Gauge.new(name: :pool_size, help: "MongoDB Connections pool size")
	Gauge.set([name: :pool_size], 365)
	- assert <<57,10,9,112,111,111,108,95,115,105,122,101,18,29,77,111,
	- 110,103,111,68,66,32,67,111,110,110,101,99,116,105,111,
	- 110,115,32,112,111,111,108,32,115,105,122,101,24,1,34,
	- 11,18,9,9,0,0,0,0,0,208,118,64>> == Prometheus.Format.Protobuf.format()
	+
	+ assert <<57, 10, 9, 112, 111, 111, 108, 95, 115, 105, 122, 101, 18, 29, 77, 111, 110,
	+ 103, 111, 68, 66, 32, 67, 111, 110, 110, 101, 99, 116, 105, 111, 110, 115,
	+ 32, 112, 111, 111, 108, 32, 115, 105, 122, 101, 24, 1, 34, 11, 18, 9, 9, 0,
	+ 0, 0, 0, 0, 208, 118, 64>> == Prometheus.Format.Protobuf.format()
	end

	test "counter" do
	- Counter.new([name: :http_requests_total, help: "Http request count"])
	- Counter.inc([name: :http_requests_total])
	- assert <<56,10,19,104,116,116,112,95,114,101,113,117,101,115,116,
	- 115,95,116,111,116,97,108,18,18,72,116,116,112,32,114,
	- 101,113,117,101,115,116,32,99,111,117,110,116,24,0,34,
	- 11,26,9,9,0,0,0,0,0,0,240,63>> == Prometheus.Format.Protobuf.format()
	+ Counter.new(name: :http_requests_total, help: "Http request count")
	+ Counter.inc(name: :http_requests_total)
	+
	+ assert <<56, 10, 19, 104, 116, 116, 112, 95, 114, 101, 113, 117, 101, 115, 116, 115,
	+ 95, 116, 111, 116, 97, 108, 18, 18, 72, 116, 116, 112, 32, 114, 101, 113,
	+ 117, 101, 115, 116, 32, 99, 111, 117, 110, 116, 24, 0, 34, 11, 26, 9, 9, 0,
	+ 0, 0, 0, 0, 0, 240, 63>> == Prometheus.Format.Protobuf.format()
	end

	test "dcounter" do
	- Counter.new([name: :dtest, help: "qw\"\\e"])
	- Counter.dinc([name: :dtest], 1.5)
	- Counter.dinc([name: :dtest], 3.5)
	- Counter.dinc([name: :dtest], 1.5)
	- :timer.sleep(10)
	- assert <<29,10,5,100,116,101,115,116,18,5,113,119,34,92,101,24,0,
	- 34,11,26,9,9,0,0,0,0,0,0,26,64>> == Prometheus.Format.Protobuf.format()
	+ Counter.new(name: :dtest, help: "qw\"\\e")
	+ Counter.inc([name: :dtest], 1.5)
	+ Counter.inc([name: :dtest], 3.5)
	+ Counter.inc([name: :dtest], 1.5)
	+
	+ assert <<29, 10, 5, 100, 116, 101, 115, 116, 18, 5, 113, 119, 34, 92, 101, 24, 0, 34,
	+ 11, 26, 9, 9, 0, 0, 0, 0, 0, 0, 26,
	+ 64>> == Prometheus.Format.Protobuf.format()
	end

	test "summary" do
	- Summary.new([name: :orders_summary, help: "Track orders count/total sum"])
	+ Summary.new(name: :orders_summary, help: "Track orders count/total sum")
	Summary.observe([name: :orders_summary], 10)
	Summary.observe([name: :orders_summary], 15)
	- assert <<63,10,14,111,114,100,101,114,115,95,115,117,109,109,97,
	- 114,121,18,28,84,114,97,99,107,32,111,114,100,101,114,
	- 115,32,99,111,117,110,116,47,116,111,116,97,108,32,115,
	- 117,109,24,2,34,13,34,11,8,2,17,0,0,0,0,0,0,57,64>> ==
	- Prometheus.Format.Protobuf.format()
	+
	+ assert <<63, 10, 14, 111, 114, 100, 101, 114, 115, 95, 115, 117, 109, 109, 97, 114,
	+ 121, 18, 28, 84, 114, 97, 99, 107, 32, 111, 114, 100, 101, 114, 115, 32, 99,
	+ 111, 117, 110, 116, 47, 116, 111, 116, 97, 108, 32, 115, 117, 109, 24, 2, 34,
	+ 13, 34, 11, 8, 2, 17, 0, 0, 0, 0, 0, 0, 57,
	+ 64>> == Prometheus.Format.Protobuf.format()
	end

	test "dsummary" do
	- Summary.new([name: :dsummary, help: "qwe"])
	- Summary.dobserve([name: :dsummary], 1.5)
	- Summary.dobserve([name: :dsummary], 2.7)
	- :timer.sleep(10)
	- assert <<32,10,8,100,115,117,109,109,97,114,121,18,3,113,119,101,
	- 24,2,34,13,34,11,8,2,17,205,204,204,204,204,204,16,64>> ==
	- Prometheus.Format.Protobuf.format()
	+ Summary.new(name: :dsummary, help: "qwe")
	+ Summary.observe([name: :dsummary], 1.5)
	+ Summary.observe([name: :dsummary], 2.7)
	+
	+ assert <<32, 10, 8, 100, 115, 117, 109, 109, 97, 114, 121, 18, 3, 113, 119, 101, 24,
	+ 2, 34, 13, 34, 11, 8, 2, 17, 205, 204, 204, 204, 204, 204, 16,
	+ 64>> == Prometheus.Format.Protobuf.format()
	end

	test "histogram" do
	- Histogram.new([name: :http_request_duration_milliseconds,
	- labels: [:method],
	- buckets: [100, 300, 500, 750, 1000],
	- help: "Http Request execution time",
	- duration_unit: false])
	+ Histogram.new(
	+ name: :http_request_duration_milliseconds,
	+ labels: [:method],
	+ buckets: [100, 300, 500, 750, 1000],
	+ help: "Http Request execution time",
	+ duration_unit: false
	+ )
	+
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 95)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 100)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 102)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 150)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 250)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 75)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 350)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 550)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 950)

	- assert <<175,1,10,34,104,116,116,112,95,114,101,113,117,101,115,
	- 116,95,100,117,114,97,116,105,111,110,95,109,105,108,
	- 108,105,115,101,99,111,110,100,115,18,27,72,116,116,112,
	- 32,82,101,113,117,101,115,116,32,101,120,101,99,117,116,
	- 105,111,110,32,116,105,109,101,24,4,34,106,10,13,10,6,
	- 109,101,116,104,111,100,18,3,103,101,116,58,89,8,9,17,0,
	- 0,0,0,0,124,164,64,26,11,8,3,17,0,0,0,0,0,0,89,64,26,11,
	- 8,6,17,0,0,0,0,0,192,114,64,26,11,8,7,17,0,0,0,0,0,64,
	- 127,64,26,11,8,8,17,0,0,0,0,0,112,135,64,26,11,8,9,17,0,
	- 0,0,0,0,64,143,64,26,11,8,9,17,0,0,0,0,0,0,240,127>> ==
	- Prometheus.Format.Protobuf.format()
	-
	+ assert <<175, 1, 10, 34, 104, 116, 116, 112, 95, 114, 101, 113, 117, 101, 115, 116,
	+ 95, 100, 117, 114, 97, 116, 105, 111, 110, 95, 109, 105, 108, 108, 105, 115,
	+ 101, 99, 111, 110, 100, 115, 18, 27, 72, 116, 116, 112, 32, 82, 101, 113,
	+ 117, 101, 115, 116, 32, 101, 120, 101, 99, 117, 116, 105, 111, 110, 32, 116,
	+ 105, 109, 101, 24, 4, 34, 106, 10, 13, 10, 6, 109, 101, 116, 104, 111, 100,
	+ 18, 3, 103, 101, 116, 58, 89, 8, 9, 17, 0, 0, 0, 0, 0, 124, 164, 64, 26, 11,
	+ 8, 3, 17, 0, 0, 0, 0, 0, 0, 89, 64, 26, 11, 8, 6, 17, 0, 0, 0, 0, 0, 192,
	+ 114, 64, 26, 11, 8, 7, 17, 0, 0, 0, 0, 0, 64, 127, 64, 26, 11, 8, 8, 17, 0,
	+ 0, 0, 0, 0, 112, 135, 64, 26, 11, 8, 9, 17, 0, 0, 0, 0, 0, 64, 143, 64, 26,
	+ 11, 8, 9, 17, 0, 0, 0, 0, 0, 0, 240,
	+ 127>> == Prometheus.Format.Protobuf.format()
	end

	test "dhistogram" do
	- Histogram.new([name: :http_request_duration_milliseconds,
	- labels: [:method],
	- buckets: [100, 300, 500, 750, 1000],
	- help: "Http Request execution time",
	- duration_unit: false])
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 500.2)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 150.4)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 450.5)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 850.3)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 750.9)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 1650.23)
	-
	- :timer.sleep(10)
	-
	- assert <<176,1,10,34,104,116,116,112,95,114,101,113,117,101,115,
	- 116,95,100,117,114,97,116,105,111,110,95,109,105,108,
	- 108,105,115,101,99,111,110,100,115,18,27,72,116,116,112,
	- 32,82,101,113,117,101,115,116,32,101,120,101,99,117,116,
	- 105,111,110,32,116,105,109,101,24,4,34,107,10,14,10,6,
	- 109,101,116,104,111,100,18,4,112,111,115,116,58,89,8,6,
	- 17,225,122,20,174,135,0,177,64,26,11,8,0,17,0,0,0,0,0,0,
	- 89,64,26,11,8,1,17,0,0,0,0,0,192,114,64,26,11,8,2,17,0,
	- 0,0,0,0,64,127,64,26,11,8,3,17,0,0,0,0,0,112,135,64,26,
	- 11,8,5,17,0,0,0,0,0,64,143,64,26,11,8,6,17,0,0,0,0,0,0,
	- 240,127>> == Prometheus.Format.Protobuf.format()
	+ Histogram.new(
	+ name: :http_request_duration_milliseconds,
	+ labels: [:method],
	+ buckets: [100, 300, 500, 750, 1000],
	+ help: "Http Request execution time",
	+ duration_unit: false
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 500.2
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 150.4
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 450.5
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 850.3
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 750.9
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 1650.23
	+ )

	+ assert <<176, 1, 10, 34, 104, 116, 116, 112, 95, 114, 101, 113, 117, 101, 115, 116,
	+ 95, 100, 117, 114, 97, 116, 105, 111, 110, 95, 109, 105, 108, 108, 105, 115,
	+ 101, 99, 111, 110, 100, 115, 18, 27, 72, 116, 116, 112, 32, 82, 101, 113,
	+ 117, 101, 115, 116, 32, 101, 120, 101, 99, 117, 116, 105, 111, 110, 32, 116,
	+ 105, 109, 101, 24, 4, 34, 107, 10, 14, 10, 6, 109, 101, 116, 104, 111, 100,
	+ 18, 4, 112, 111, 115, 116, 58, 89, 8, 6, 17, 225, 122, 20, 174, 135, 0, 177,
	+ 64, 26, 11, 8, 0, 17, 0, 0, 0, 0, 0, 0, 89, 64, 26, 11, 8, 1, 17, 0, 0, 0, 0,
	+ 0, 192, 114, 64, 26, 11, 8, 2, 17, 0, 0, 0, 0, 0, 64, 127, 64, 26, 11, 8, 3,
	+ 17, 0, 0, 0, 0, 0, 112, 135, 64, 26, 11, 8, 5, 17, 0, 0, 0, 0, 0, 64, 143,
	+ 64, 26, 11, 8, 6, 17, 0, 0, 0, 0, 0, 0, 240,
	+ 127>> == Prometheus.Format.Protobuf.format()
	end
	end
	diff --git a/test/format/text_test.exs b/test/format/text_test.exs
	index 823718e..e7118b3 100644
	--- a/test/format/text_test.exs
	+++ b/test/format/text_test.exs
	@@ -1,142 +1,151 @@
	defmodule Prometheus.Format.TextTest do
	use Prometheus.Case

	require Prometheus.Format.Text

	test "content_type" do
	- assert "text/plain; version=0.0.4" == Prometheus.Format.Text.content_type
	+ assert "text/plain; version=0.0.4" == Prometheus.Format.Text.content_type()
	end

	test "gauge" do
	- Gauge.new([name: :pool_size, help: "MongoDB Connections pool size"])
	+ Gauge.new(name: :pool_size, help: "MongoDB Connections pool size")
	Gauge.set([name: :pool_size], 365)
	+
	assert ~s"""
	- # TYPE pool_size gauge
	- # HELP pool_size MongoDB Connections pool size
	- pool_size 365
	+ # TYPE pool_size gauge
	+ # HELP pool_size MongoDB Connections pool size
	+ pool_size 365

	- """
	- == Prometheus.Format.Text.format()
	+ """ == Prometheus.Format.Text.format()
	end

	test "counter" do
	- Counter.new([name: :http_requests_total, help: "Http request count"])
	- Counter.inc([name: :http_requests_total])
	+ Counter.new(name: :http_requests_total, help: "Http request count")
	+ Counter.inc(name: :http_requests_total)
	+
	assert ~s"""
	- # TYPE http_requests_total counter
	- # HELP http_requests_total Http request count
	- http_requests_total 1
	+ # TYPE http_requests_total counter
	+ # HELP http_requests_total Http request count
	+ http_requests_total 1

	- """ == Prometheus.Format.Text.format()
	+ """ == Prometheus.Format.Text.format()
	end

	test "dcounter" do
	- Counter.new([name: :dtest, help: "qw\"\\e"])
	- Counter.dinc([name: :dtest], 1.5)
	- Counter.dinc([name: :dtest], 3.5)
	- Counter.dinc([name: :dtest], 1.5)
	- :timer.sleep(10)
	+ Counter.new(name: :dtest, help: "qw\"\\e")
	+ Counter.inc([name: :dtest], 1.5)
	+ Counter.inc([name: :dtest], 3.5)
	+ Counter.inc([name: :dtest], 1.5)
	+
	assert ~s"""
	- # TYPE dtest counter
	- # HELP dtest qw\"\\\\e
	- dtest 6.5
	+ # TYPE dtest counter
	+ # HELP dtest qw\"\\\\e
	+ dtest 6.5

	- """ == Prometheus.Format.Text.format()
	+ """ == Prometheus.Format.Text.format()
	end

	test "summary" do
	- Summary.new([name: :orders_summary, help: "Track orders count/total sum"])
	+ Summary.new(name: :orders_summary, help: "Track orders count/total sum")
	Summary.observe([name: :orders_summary], 10)
	Summary.observe([name: :orders_summary], 15)
	- assert ~s"""
	- # TYPE orders_summary summary
	- # HELP orders_summary Track orders count/total sum
	- orders_summary_count 2
	- orders_summary_sum 25
	+ Summary.observe([name: :orders_summary], 1.5)
	+ Summary.observe([name: :orders_summary], 2.7)

	- """ == Prometheus.Format.Text.format()
	- end
	-
	- test "dsummary" do
	- Summary.new([name: :dsummary, help: "qwe"])
	- Summary.dobserve([name: :dsummary], 1.5)
	- Summary.dobserve([name: :dsummary], 2.7)
	- :timer.sleep(10)
	assert ~s"""
	- # TYPE dsummary summary
	- # HELP dsummary qwe
	- dsummary_count 2
	- dsummary_sum 4.2
	+ # TYPE orders_summary summary
	+ # HELP orders_summary Track orders count/total sum
	+ orders_summary_count 4
	+ orders_summary_sum 29.2

	- """ == Prometheus.Format.Text.format()
	+ """ == Prometheus.Format.Text.format()
	end

	test "histogram" do
	- Histogram.new([name: :http_request_duration_milliseconds,
	- labels: [:method],
	- buckets: [100, 300, 500, 750, 1000],
	- help: "Http Request execution time",
	- duration_unit: false])
	+ Histogram.new(
	+ name: :http_request_duration_milliseconds,
	+ labels: [:method],
	+ buckets: [100, 300, 500, 750, 1000],
	+ help: "Http Request execution time",
	+ duration_unit: false
	+ )
	+
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 95)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 100)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 102)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 150)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 250)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 75)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 350)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 550)
	Histogram.observe([name: :http_request_duration_milliseconds, labels: [:get]], 950)

	assert ~s"""
	- # TYPE http_request_duration_milliseconds histogram
	- # HELP http_request_duration_milliseconds Http Request execution time
	- http_request_duration_milliseconds_bucket{method="get",le="100"} 3
	- http_request_duration_milliseconds_bucket{method="get",le="300"} 6
	- http_request_duration_milliseconds_bucket{method="get",le="500"} 7
	- http_request_duration_milliseconds_bucket{method="get",le="750"} 8
	- http_request_duration_milliseconds_bucket{method="get",le="1000"} 9
	- http_request_duration_milliseconds_bucket{method="get",le="+Inf"} 9
	- http_request_duration_milliseconds_count{method="get"} 9
	- http_request_duration_milliseconds_sum{method="get"} 2622
	-
	- """ == Prometheus.Format.Text.format()
	-
	+ # TYPE http_request_duration_milliseconds histogram
	+ # HELP http_request_duration_milliseconds Http Request execution time
	+ http_request_duration_milliseconds_bucket{method="get",le="100"} 3
	+ http_request_duration_milliseconds_bucket{method="get",le="300"} 6
	+ http_request_duration_milliseconds_bucket{method="get",le="500"} 7
	+ http_request_duration_milliseconds_bucket{method="get",le="750"} 8
	+ http_request_duration_milliseconds_bucket{method="get",le="1000"} 9
	+ http_request_duration_milliseconds_bucket{method="get",le="+Inf"} 9
	+ http_request_duration_milliseconds_count{method="get"} 9
	+ http_request_duration_milliseconds_sum{method="get"} 2622
	+
	+ """ == Prometheus.Format.Text.format()
	end

	test "dhistogram" do
	- Histogram.new([name: :http_request_duration_milliseconds,
	- labels: [:method],
	- buckets: [100, 300, 500, 750, 1000],
	- help: "Http Request execution time",
	- duration_unit: false])
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 500.2)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 150.4)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 450.5)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 850.3)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 750.9)
	- Histogram.dobserve(
	- [name: :http_request_duration_milliseconds, labels: [:post]], 1650.23)
	-
	- :timer.sleep(10)
	+ Histogram.new(
	+ name: :http_request_duration_milliseconds,
	+ labels: [:method],
	+ buckets: [100, 300, 500, 750, 1000],
	+ help: "Http Request execution time",
	+ duration_unit: false
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 500.2
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 150.4
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 450.5
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 850.3
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 750.9
	+ )
	+
	+ Histogram.observe(
	+ [name: :http_request_duration_milliseconds, labels: [:post]],
	+ 1650.23
	+ )

	assert ~s"""
	- # TYPE http_request_duration_milliseconds histogram
	- # HELP http_request_duration_milliseconds Http Request execution time
	- http_request_duration_milliseconds_bucket{method=\"post\",le=\"100\"} 0
	- http_request_duration_milliseconds_bucket{method=\"post\",le=\"300\"} 1
	- http_request_duration_milliseconds_bucket{method=\"post\",le=\"500\"} 2
	- http_request_duration_milliseconds_bucket{method=\"post\",le=\"750\"} 3
	- http_request_duration_milliseconds_bucket{method=\"post\",le=\"1000\"} 5
	- http_request_duration_milliseconds_bucket{method=\"post\",le=\"+Inf\"} 6
	- http_request_duration_milliseconds_count{method=\"post\"} 6
	- http_request_duration_milliseconds_sum{method=\"post\"} 4352.53
	-
	- """ == Prometheus.Format.Text.format()
	-
	+ # TYPE http_request_duration_milliseconds histogram
	+ # HELP http_request_duration_milliseconds Http Request execution time
	+ http_request_duration_milliseconds_bucket{method=\"post\",le=\"100\"} 0
	+ http_request_duration_milliseconds_bucket{method=\"post\",le=\"300\"} 1
	+ http_request_duration_milliseconds_bucket{method=\"post\",le=\"500\"} 2
	+ http_request_duration_milliseconds_bucket{method=\"post\",le=\"750\"} 3
	+ http_request_duration_milliseconds_bucket{method=\"post\",le=\"1000\"} 5
	+ http_request_duration_milliseconds_bucket{method=\"post\",le=\"+Inf\"} 6
	+ http_request_duration_milliseconds_count{method=\"post\"} 6
	+ http_request_duration_milliseconds_sum{method=\"post\"} 4352.53
	+
	+ """ == Prometheus.Format.Text.format()
	end
	end
	diff --git a/test/injector_test.exs b/test/injector_test.exs
	index c697cdd..ade3193 100644
	--- a/test/injector_test.exs
	+++ b/test/injector_test.exs
	@@ -1,158 +1,160 @@
	defmodule Injector do
	-
	defmacro test(ast) do
	- Prometheus.Injector.inject(fn(block) ->
	- quote do
	- try do
	- IO.puts("before block")
	- unquote(block)
	- after
	- IO.puts("after block")
	+ Prometheus.Injector.inject(
	+ fn block ->
	+ quote do
	+ try do
	+ IO.puts("before block")
	+ unquote(block)
	+ after
	+ IO.puts("after block")
	+ end
	end
	- end
	- end, __CALLER__, ast)
	+ end,
	+ __CALLER__,
	+ ast
	+ )
	end
	-
	end

	defmodule Prometheus.InjectorTest do
	use Prometheus.Case

	require Injector

	Injector.test do
	def fun1() do
	IO.puts("fun1")
	end

	def fun2() do
	IO.puts("fun2")
	end

	Injector.test do
	def fun3() do
	IO.puts("fun3")
	rescue
	e in RuntimeError ->
	IO.puts(e)
	end
	end
	end

	def do_dangerous_work(x) do
	Injector.test do
	IO.puts("Doing dangerous work #{x}")
	rescue
	_ -> IO.puts("Died")
	after
	IO.puts("Done anyway")
	end
	end

	test "fn" do
	assert capture_io(fn ->
	- Injector.test(fn () -> IO.puts("qwe") end)
	- end) ==
	- "before block\nqwe\nafter block\n"
	+ Injector.test(fn -> IO.puts("qwe") end)
	+ end) == "before block\nqwe\nafter block\n"
	end

	test "blocks" do
	- assert capture_io(fn () ->
	- Injector.test IO.puts("qwe")
	- end) == "before block\nqwe\nafter block\n"
	-
	- assert capture_io(fn () ->
	- Injector.test do: IO.puts("qwe")
	- end) == "before block\nqwe\nafter block\n"
	-
	- assert capture_io(fn () ->
	- Injector.test do
	- IO.puts("qwe")
	- IO.puts("qwa")
	- end
	- end) == "before block\nqwe\nqwa\nafter block\n"
	+ assert capture_io(fn ->
	+ Injector.test(IO.puts("qwe"))
	+ end) == "before block\nqwe\nafter block\n"
	+
	+ assert capture_io(fn ->
	+ Injector.test(do: IO.puts("qwe"))
	+ end) == "before block\nqwe\nafter block\n"
	+
	+ assert capture_io(fn ->
	+ Injector.test do
	+ IO.puts("qwe")
	+ IO.puts("qwa")
	+ end
	+ end) == "before block\nqwe\nqwa\nafter block\n"
	end

	test "implicit try" do
	- assert capture_io(fn () ->
	- do_dangerous_work(5)
	- end) == "before block\nDoing dangerous work 5\nDone anyway\nafter block\n"
	+ assert capture_io(fn ->
	+ do_dangerous_work(5)
	+ end) == "before block\nDoing dangerous work 5\nDone anyway\nafter block\n"

	- assert capture_io(fn () ->
	- do_dangerous_work({})
	- end) == "before block\nDied\nDone anyway\nafter block\n"
	+ assert capture_io(fn ->
	+ do_dangerous_work({})
	+ end) == "before block\nDied\nDone anyway\nafter block\n"
	end

	test "defs" do
	- assert capture_io(fn () ->
	- fun1()
	- end) == "before block\nfun1\nafter block\n"
	+ assert capture_io(fn ->
	+ fun1()
	+ end) == "before block\nfun1\nafter block\n"

	- assert capture_io(fn () ->
	- fun2()
	- end) == "before block\nfun2\nafter block\n"
	+ assert capture_io(fn ->
	+ fun2()
	+ end) == "before block\nfun2\nafter block\n"

	- assert capture_io(fn () ->
	- fun3()
	- end) == "before block\nbefore block\nfun3\nafter block\nafter block\n"
	+ assert capture_io(fn ->
	+ fun3()
	+ end) == "before block\nbefore block\nfun3\nafter block\nafter block\n"
	end

	defmodule QweInjector do
	defmacro inject_(body) do
	- Prometheus.Injector.inject_(body, fn(b) ->
	+ Prometheus.Injector.inject_(body, fn b ->
	quote do
	IO.puts("qwe")
	+
	try do
	unquote(b)
	after
	IO.puts("after_qwe")
	end
	end
	end)
	end
	+
	defmacro inject1(body) do
	body
	end
	end

	defmodule UsefulModule do
	require QweInjector

	def do_work(x) do
	QweInjector.inject_ do
	- IO.puts("Doing work #{inspect x}")
	+ IO.puts("Doing work #{inspect(x)}")
	end
	end

	def do_dangerous_work(x) do
	QweInjector.inject_ do
	IO.puts("Doing dangerous work #{x}")
	rescue
	_ -> IO.puts("Died")
	after
	IO.puts("Done anyway")
	end
	end

	QweInjector.inject_ do
	def mildly_interesting(what) do
	IO.puts("#{what} is mildly interesting")
	end

	def wtf(what) do
	IO.puts("#{what} is wtf")
	rescue
	- _ -> IO.puts("Oh my, #{inspect what} is real wtf")
	+ _ -> IO.puts("Oh my, #{inspect(what)} is real wtf")
	else
	_ -> IO.puts("Saw wtf and still stronk")
	end
	end
	end

	test "UsefulModule" do
	- assert capture_io(fn () ->
	- UsefulModule.wtf({})
	- end) ==
	- "qwe\nOh my, {} is real wtf\nafter_qwe\n"
	+ assert capture_io(fn ->
	+ UsefulModule.wtf({})
	+ end) == "qwe\nOh my, {} is real wtf\nafter_qwe\n"
	end
	end
	diff --git a/test/metric/boolean_test.exs b/test/metric/boolean_test.exs
	index 94a5ba9..20d5943 100644
	--- a/test/metric/boolean_test.exs
	+++ b/test/metric/boolean_test.exs
	@@ -1,210 +1,193 @@
	defmodule Prometheus.BooleanTest do
	use Prometheus.Case

	test "registration" do
	- spec = [name: :name,
	- help: "",
	- registry: :qwe]
	+ spec = [name: :name, help: "", registry: :qwe]

	assert true == Boolean.declare(spec)
	assert false == Boolean.declare(spec)
	- assert_raise Prometheus.MFAlreadyExistsError,
	- "Metric qwe:name already exists.",
	- fn ->
	+
	+ assert_raise Prometheus.MFAlreadyExistsError, "Metric qwe:name already exists.", fn ->
	Boolean.new(spec)
	end
	end

	test "spec errors" do
	assert_raise Prometheus.MissingMetricSpecKeyError,
	- "Required key name is missing from metric spec.",
	- fn ->
	- Boolean.new([help: ""])
	- end
	- assert_raise Prometheus.InvalidMetricNameError,
	- "Invalid metric name: 12.",
	- fn ->
	- Boolean.new([name: 12, help: ""])
	+ "Required key name is missing from metric spec.",
	+ fn ->
	+ Boolean.new(help: "")
	+ end
	+
	+ assert_raise Prometheus.InvalidMetricNameError, "Invalid metric name: 12.", fn ->
	+ Boolean.new(name: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricLabelsError,
	- "Invalid metric labels: 12.",
	- fn ->
	- Boolean.new([name: "qwe", labels: 12, help: ""])
	+
	+ assert_raise Prometheus.InvalidMetricLabelsError, "Invalid metric labels: 12.", fn ->
	+ Boolean.new(name: "qwe", labels: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricHelpError,
	- "Invalid metric help: 12.",
	- fn ->
	- Boolean.new([name: "qwe", help: 12])
	+
	+ assert_raise Prometheus.InvalidMetricHelpError, "Invalid metric help: 12.", fn ->
	+ Boolean.new(name: "qwe", help: 12)
	end
	end

	test "boolean specific errors" do
	- spec = [name: :fuse_state,
	- labels: [:qwe],
	- help: ""]
	+ spec = [name: :fuse_state, labels: [:qwe], help: ""]

	Boolean.declare(spec)

	## set
	assert_raise Prometheus.InvalidValueError,
	- "Invalid value: %{} (value is not boolean).",
	- fn ->
	- Boolean.set(spec, %{})
	- end
	+ "Invalid value: %{} (value is not boolean).",
	+ fn ->
	+ Boolean.set(spec, %{})
	+ end

	## toggle

	Boolean.set(spec, :undefined)
	+
	assert_raise Prometheus.InvalidValueError,
	- "Invalid value: :undefined (can't toggle undefined boolean).",
	- fn ->
	- Boolean.toggle(spec)
	- end
	+ "Invalid value: :undefined (can't toggle undefined boolean).",
	+ fn ->
	+ Boolean.toggle(spec)
	+ end
	end

	test "mf/arity errors" do
	- spec = [name: :metric_with_label,
	- labels: [:label],
	- help: ""]
	+ spec = [name: :metric_with_label, labels: [:label], help: ""]
	Boolean.declare(spec)

	## set
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Boolean.set(:unknown_metric, true)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Boolean.set(:unknown_metric, true)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Boolean.set([name: :metric_with_label, labels: [:l1, :l2]], true)
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Boolean.set([name: :metric_with_label, labels: [:l1, :l2]], true)
	+ end

	## toggle
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Boolean.toggle(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Boolean.toggle(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Boolean.toggle([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Boolean.toggle(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## remove
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Boolean.remove(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Boolean.remove(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Boolean.remove([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Boolean.remove(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## reset
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Boolean.reset(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Boolean.reset(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Boolean.reset([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Boolean.reset(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## value
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Boolean.value(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Boolean.value(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Boolean.value([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Boolean.value(name: :metric_with_label, labels: [:l1, :l2])
	+ end
	end

	test "set" do
	- spec = [name: :fuse_state,
	- labels: [:name],
	- help: ""]
	+ spec = [name: :fuse_state, labels: [:name], help: ""]
	Boolean.new(spec)

	Boolean.set(spec, 110)
	assert true == Boolean.value(spec)
	Boolean.set(spec, 0)
	assert false == Boolean.value(spec)
	Boolean.set(spec, true)
	assert true == Boolean.value(spec)
	Boolean.set(spec, false)
	assert false == Boolean.value(spec)
	Boolean.set(spec, [1])
	assert true == Boolean.value(spec)
	Boolean.set(spec, [])
	assert false == Boolean.value(spec)
	Boolean.reset(spec)
	assert false == Boolean.value(spec)
	end

	test "toggle" do
	- spec = [name: :fuse_state,
	- labels: [:name],
	- help: ""]
	+ spec = [name: :fuse_state, labels: [:name], help: ""]
	Boolean.new(spec)

	Boolean.set(spec, 110)
	assert true == Boolean.value(spec)
	Boolean.toggle(spec)
	assert false == Boolean.value(spec)
	Boolean.toggle(spec)
	assert true == Boolean.value(spec)
	end

	test "remove" do
	- fuse_state = [name: :fuse_state,
	- labels: [:name],
	- help: ""]
	+ fuse_state = [name: :fuse_state, labels: [:name], help: ""]
	Boolean.new(fuse_state)

	- simple_boolean = [name: :simple_boolean,
	- labels: [],
	- help: ""]
	+ simple_boolean = [name: :simple_boolean, labels: [], help: ""]
	Boolean.new(simple_boolean)

	Boolean.set(fuse_state, true)
	Boolean.set(simple_boolean, true)

	assert true == Boolean.value(fuse_state)
	assert true == Boolean.value(simple_boolean)

	assert true == Boolean.remove(fuse_state)
	assert true == Boolean.remove(simple_boolean)

	assert :undefined == Boolean.value(fuse_state)
	assert :undefined == Boolean.value(simple_boolean)

	assert false == Boolean.remove(fuse_state)
	assert false == Boolean.remove(simple_boolean)
	end

	test "default value" do
	- fuse_state = [name: :fuse_state,
	- labels: [:name],
	- help: ""]
	+ fuse_state = [name: :fuse_state, labels: [:name], help: ""]
	Boolean.new(fuse_state)

	- simple_boolean = [name: :simple_boolean,
	- labels: [],
	- help: ""]
	+ simple_boolean = [name: :simple_boolean, labels: [], help: ""]
	Boolean.new(simple_boolean)

	assert :undefined == Boolean.value(fuse_state)
	assert :undefined == Boolean.value(simple_boolean)
	end
	-
	end
	diff --git a/test/metric/counter_test.exs b/test/metric/counter_test.exs
	index 3b96625..d1f66bd 100644
	--- a/test/metric/counter_test.exs
	+++ b/test/metric/counter_test.exs
	@@ -1,312 +1,261 @@
	defmodule Prometheus.CounterTest do
	use Prometheus.Case

	test "registration" do
	- spec = [name: :name,
	- help: "",
	- registry: :qwe]
	+ spec = [name: :name, help: "", registry: :qwe]

	assert true == Counter.declare(spec)
	assert false == Counter.declare(spec)
	- assert_raise Prometheus.MFAlreadyExistsError,
	- "Metric qwe:name already exists.",
	- fn ->
	+
	+ assert_raise Prometheus.MFAlreadyExistsError, "Metric qwe:name already exists.", fn ->
	Counter.new(spec)
	end
	end

	test "spec errors" do
	assert_raise Prometheus.MissingMetricSpecKeyError,
	- "Required key name is missing from metric spec.",
	- fn ->
	- Counter.new([help: ""])
	- end
	- assert_raise Prometheus.InvalidMetricNameError,
	- "Invalid metric name: 12.",
	- fn ->
	- Counter.new([name: 12, help: ""])
	+ "Required key name is missing from metric spec.",
	+ fn ->
	+ Counter.new(help: "")
	+ end
	+
	+ assert_raise Prometheus.InvalidMetricNameError, "Invalid metric name: 12.", fn ->
	+ Counter.new(name: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricLabelsError,
	- "Invalid metric labels: 12.",
	- fn ->
	- Counter.new([name: "qwe", labels: 12, help: ""])
	+
	+ assert_raise Prometheus.InvalidMetricLabelsError, "Invalid metric labels: 12.", fn ->
	+ Counter.new(name: "qwe", labels: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricHelpError,
	- "Invalid metric help: 12.",
	- fn ->
	- Counter.new([name: "qwe", help: 12])
	+
	+ assert_raise Prometheus.InvalidMetricHelpError, "Invalid metric help: 12.", fn ->
	+ Counter.new(name: "qwe", help: 12)
	end
	end

	test "counter specific errors" do
	- spec = [name: :http_requests_total,
	- help: ""]
	+ spec = [name: :http_requests_total, help: ""]

	## inc
	assert_raise Prometheus.InvalidValueError,
	- "Invalid value: -1 (inc accepts only non-negative integers).",
	- fn ->
	- Counter.inc(spec, -1)
	- end
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: 1.5 (inc accepts only non-negative integers).",
	- fn ->
	- Counter.inc(spec, 1.5)
	- end
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (inc accepts only non-negative integers).",
	- fn ->
	- Counter.inc(spec, "qwe")
	- end
	+ "Invalid value: -1 (inc accepts only non-negative numbers).",
	+ fn ->
	+ Counter.inc(spec, -1)
	+ end

	- ## dinc
	assert_raise Prometheus.InvalidValueError,
	- "Invalid value: -1 (dinc accepts only non-negative numbers).",
	- fn ->
	- Counter.dinc(spec, -1)
	- end
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (dinc accepts only non-negative numbers).",
	- fn ->
	- Counter.dinc(spec, "qwe")
	- end
	+ "Invalid value: \"qwe\" (inc accepts only non-negative numbers).",
	+ fn ->
	+ Counter.inc(spec, "qwe")
	+ end
	end

	test "mf/arity errors" do
	- spec = [name: :metric_with_label,
	- labels: [:label],
	- help: ""]
	+ spec = [name: :metric_with_label, labels: [:label], help: ""]
	Counter.declare(spec)

	## inc
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Counter.inc(:unknown_metric)
	- end
	- assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Counter.inc([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Counter.inc(:unknown_metric)
	+ end

	- ## dinc
	- assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Counter.dinc(:unknown_metric)
	- end
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Counter.dinc([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Counter.inc(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## remove
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Counter.remove(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Counter.remove(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Counter.remove([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Counter.remove(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## reset
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Counter.reset(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Counter.reset(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Counter.reset([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Counter.reset(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## value
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Counter.value(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Counter.value(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Counter.value([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Counter.value(name: :metric_with_label, labels: [:l1, :l2])
	+ end
	end

	test "inc" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	Counter.new(spec)

	Counter.inc(spec)
	Counter.inc(spec, 3)
	- assert 4 == Counter.value(spec)
	-
	- Counter.reset(spec)
	-
	- assert 0 == Counter.value(spec)
	- end
	-
	- test "dinc" do
	- spec = [name: :http_requests_total,
	- help: ""]
	- Counter.new(spec)
	-
	- Counter.dinc(spec)
	- Counter.dinc(spec, 3.5)
	+ Counter.inc(spec)
	+ Counter.inc(spec, 3.5)

	- ## dinc is async. let's make sure gen_server processed our request
	- Process.sleep(10)
	- assert 4.5 == Counter.value(spec)
	+ assert 8.5 == Counter.value(spec)

	Counter.reset(spec)

	assert 0 == Counter.value(spec)
	end

	test "remove" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	- wl_spec = [name: :simple_counter,
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	+ wl_spec = [name: :simple_counter, help: ""]

	Counter.new(spec)
	Counter.new(wl_spec)

	Counter.inc(spec)
	Counter.inc(wl_spec)

	assert 1 == Counter.value(spec)
	assert 1 == Counter.value(wl_spec)

	assert true == Counter.remove(spec)
	assert true == Counter.remove(wl_spec)

	assert :undefined == Counter.value(spec)
	assert :undefined == Counter.value(wl_spec)

	assert false == Counter.remove(spec)
	assert false == Counter.remove(wl_spec)
	end

	test "default value" do
	- lspec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	+ lspec = [name: :http_requests_total, labels: [:method], help: ""]
	Counter.new(lspec)

	assert :undefined == Counter.value(lspec)

	- spec = [name: :something_total,
	- labels: [],
	- help: ""]
	+ spec = [name: :something_total, labels: [], help: ""]
	Counter.new(spec)

	assert 0 == Counter.value(spec)
	end

	defmodule CounterInjectorsTest do
	-
	use Prometheus.Metric

	@counter name: :calls_total, help: ""
	@counter name: :sometimes_total, help: ""
	@counter name: :exceptions_total, help: ""
	@counter name: :no_exceptions_total, help: ""

	Counter.count name: :calls_total do
	def decorated_fun() do
	IO.puts("I'm decorated fun")
	end

	def decorated_fun1() do
	IO.puts("I'm decorated fun1")
	IO.puts("I'm decorated fun1")
	end
	end

	def sometimes_count(arg) do
	if arg do
	- Counter.count [name: :sometimes_total], do: IO.puts "Called indeed!"
	+ Counter.count([name: :sometimes_total], do: IO.puts("Called indeed!"))
	else
	IO.puts("Not this time")
	end
	end

	- Counter.count_no_exceptions [name: :no_exceptions_total] do
	+ Counter.count_no_exceptions name: :no_exceptions_total do
	Counter.count_exceptions [name: :exceptions_total], ArithmeticError do
	def sometimes_raise(arg) do
	5 / arg
	end
	end

	def sometimes_raise1(arg) when is_list(arg) do
	5 / arg
	end
	end

	- def qwe () do
	- Counter.count_no_exceptions [name: :no_exceptions_total], fn () ->
	- IO.puts 1
	- IO.puts 2
	- end
	+ def qwe() do
	+ Counter.count_no_exceptions([name: :no_exceptions_total], fn ->
	+ IO.puts(1)
	+ IO.puts(2)
	+ end)
	end

	- Counter.count_exceptions [name: :exceptions_total] do
	+ Counter.count_exceptions name: :exceptions_total do
	def sometimes_raise_any(arg) do
	5 / arg
	end
	end
	end

	test "decorators test" do
	-
	CounterInjectorsTest.__declare_prometheus_metrics__()

	- assert 0 == Counter.value name: :calls_total
	+ assert 0 == Counter.value(name: :calls_total)
	+
	assert capture_io(fn -> CounterInjectorsTest.decorated_fun() end) ==
	- "I'm decorated fun\n"
	- assert 1 == Counter.value name: :calls_total
	+ "I'm decorated fun\n"
	+
	+ assert 1 == Counter.value(name: :calls_total)
	+
	assert capture_io(fn -> CounterInjectorsTest.decorated_fun1() end) ==
	- "I'm decorated fun1\nI'm decorated fun1\n"
	- assert 2 == Counter.value name: :calls_total
	+ "I'm decorated fun1\nI'm decorated fun1\n"
	+
	+ assert 2 == Counter.value(name: :calls_total)
	+
	+ assert 0 == Counter.value(name: :sometimes_total)

	- assert 0 == Counter.value name: :sometimes_total
	assert capture_io(fn -> CounterInjectorsTest.sometimes_count(true) end) ==
	- "Called indeed!\n"
	+ "Called indeed!\n"
	+
	assert capture_io(fn -> CounterInjectorsTest.sometimes_count(false) end) ==
	- "Not this time\n"
	- assert 1 == Counter.value name: :sometimes_total
	+ "Not this time\n"
	+
	+ assert 1 == Counter.value(name: :sometimes_total)

	- assert 0 == Counter.value name: :exceptions_total
	- assert 0 == Counter.value name: :no_exceptions_total
	+ assert 0 == Counter.value(name: :exceptions_total)
	+ assert 0 == Counter.value(name: :no_exceptions_total)
	assert 1 == CounterInjectorsTest.sometimes_raise(5)
	- assert 0 == Counter.value name: :exceptions_total
	- assert 1 == Counter.value name: :no_exceptions_total
	- assert_raise ArithmeticError,
	- fn ->
	+ assert 0 == Counter.value(name: :exceptions_total)
	+ assert 1 == Counter.value(name: :no_exceptions_total)
	+
	+ assert_raise ArithmeticError, fn ->
	CounterInjectorsTest.sometimes_raise(0)
	end
	- assert 1 == Counter.value name: :exceptions_total
	- assert 1 == Counter.value name: :no_exceptions_total

	- assert 1 == Counter.value name: :exceptions_total
	+ assert 1 == Counter.value(name: :exceptions_total)
	+ assert 1 == Counter.value(name: :no_exceptions_total)
	+
	+ assert 1 == Counter.value(name: :exceptions_total)
	assert 1 == CounterInjectorsTest.sometimes_raise(5)
	- assert 1 == Counter.value name: :exceptions_total
	- assert_raise ArithmeticError,
	- fn ->
	+ assert 1 == Counter.value(name: :exceptions_total)
	+
	+ assert_raise ArithmeticError, fn ->
	CounterInjectorsTest.sometimes_raise(0)
	end
	- assert 2 == Counter.value name: :exceptions_total

	+ assert 2 == Counter.value(name: :exceptions_total)
	end
	-
	end
	diff --git a/test/metric/gauge_test.exs b/test/metric/gauge_test.exs
	index c9709f0..7f7f95c 100644
	--- a/test/metric/gauge_test.exs
	+++ b/test/metric/gauge_test.exs
	@@ -1,461 +1,383 @@
	defmodule Prometheus.GaugeTest do
	use Prometheus.Case

	test "registration" do
	- spec = [name: :name,
	- help: "",
	- registry: :qwe]
	+ spec = [name: :name, help: "", registry: :qwe]

	assert true == Gauge.declare(spec)
	assert false == Gauge.declare(spec)
	- assert_raise Prometheus.MFAlreadyExistsError,
	- "Metric qwe:name already exists.",
	- fn ->
	+
	+ assert_raise Prometheus.MFAlreadyExistsError, "Metric qwe:name already exists.", fn ->
	Gauge.new(spec)
	end
	end

	test "spec errors" do
	assert_raise Prometheus.MissingMetricSpecKeyError,
	- "Required key name is missing from metric spec.",
	- fn ->
	- Gauge.new([help: ""])
	- end
	- assert_raise Prometheus.InvalidMetricNameError,
	- "Invalid metric name: 12.",
	- fn ->
	- Gauge.new([name: 12, help: ""])
	+ "Required key name is missing from metric spec.",
	+ fn ->
	+ Gauge.new(help: "")
	+ end
	+
	+ assert_raise Prometheus.InvalidMetricNameError, "Invalid metric name: 12.", fn ->
	+ Gauge.new(name: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricLabelsError,
	- "Invalid metric labels: 12.",
	- fn ->
	- Gauge.new([name: "qwe", labels: 12, help: ""])
	+
	+ assert_raise Prometheus.InvalidMetricLabelsError, "Invalid metric labels: 12.", fn ->
	+ Gauge.new(name: "qwe", labels: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricHelpError,
	- "Invalid metric help: 12.",
	- fn ->
	- Gauge.new([name: "qwe", help: 12])
	+
	+ assert_raise Prometheus.InvalidMetricHelpError, "Invalid metric help: 12.", fn ->
	+ Gauge.new(name: "qwe", help: 12)
	end
	end

	test "gauge specific errors" do
	- spec = [name: :http_requests_total,
	- help: ""]
	+ spec = [name: :http_requests_total, help: ""]

	## set
	assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (set accepts only numbers).",
	- fn ->
	- Gauge.set(spec, "qwe")
	- end
	+ "Invalid value: \"qwe\" (set accepts only numbers and 'undefined').",
	+ fn ->
	+ Gauge.set(spec, "qwe")
	+ end

	## inc
	assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (inc accepts only integers).",
	- fn ->
	- Gauge.inc(spec, "qwe")
	- end
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: -1.5 (inc accepts only integers).",
	- fn ->
	- Gauge.inc(spec, -1.5)
	- end
	+ "Invalid value: \"qwe\" (inc accepts only numbers).",
	+ fn ->
	+ Gauge.inc(spec, "qwe")
	+ end

	## dec
	assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (dec accepts only integers).",
	- fn ->
	- Gauge.dec(spec, "qwe")
	- end
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: -1.5 (dec accepts only integers).",
	- fn ->
	- Gauge.dec(spec, -1.5)
	- end
	-
	- ## dinc
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (dinc accepts only numbers).",
	- fn ->
	- Gauge.dinc(spec, "qwe")
	- end
	-
	- ## ddec
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (ddec accepts only numbers).",
	- fn ->
	- Gauge.ddec(spec, "qwe")
	- end
	+ "Invalid value: \"qwe\" (dec accepts only numbers).",
	+ fn ->
	+ Gauge.dec(spec, "qwe")
	+ end

	## track_inprogress
	assert_raise Prometheus.InvalidBlockArityError,
	- "Fn with arity 2 (args: :x, :y) passed as block.",
	- fn ->
	- Macro.expand(quote do
	- Gauge.track_inprogress(spec, fn(x, y) -> 1 + x + y end)
	- end, __ENV__)
	- end
	+ "Fn with arity 2 (args: :x, :y) passed as block.",
	+ fn ->
	+ Macro.expand(
	+ quote do
	+ Gauge.track_inprogress(spec, fn x, y -> 1 + x + y end)
	+ end,
	+ __ENV__
	+ )
	+ end

	## set_duration
	assert_raise Prometheus.InvalidBlockArityError,
	- "Fn with arity 2 (args: :x, :y) passed as block.",
	- fn ->
	- Macro.expand(quote do
	- Gauge.set_duration(spec, fn(x, y) -> 1 + x + y end)
	- end, __ENV__)
	- end
	+ "Fn with arity 2 (args: :x, :y) passed as block.",
	+ fn ->
	+ Macro.expand(
	+ quote do
	+ Gauge.set_duration(spec, fn x, y -> 1 + x + y end)
	+ end,
	+ __ENV__
	+ )
	+ end
	end

	test "mf/arity errors" do
	- spec = [name: :metric_with_label,
	- labels: [:label],
	- help: ""]
	+ spec = [name: :metric_with_label, labels: [:label], help: ""]
	Gauge.declare(spec)

	## set
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.set(:unknown_metric, 1)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Gauge.set(:unknown_metric, 1)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.set([name: :metric_with_label, labels: [:l1, :l2]], 1)
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Gauge.set([name: :metric_with_label, labels: [:l1, :l2]], 1)
	+ end

	## inc
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.inc(:unknown_metric)
	- end
	- assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.inc([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Gauge.inc(:unknown_metric)
	+ end

	- ## dinc
	- assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.dinc(:unknown_metric)
	- end
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.dinc([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Gauge.inc(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## dec
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.dec(:unknown_metric)
	- end
	- assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.dec([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Gauge.dec(:unknown_metric)
	+ end

	- ## ddec
	- assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.ddec(:unknown_metric)
	- end
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.ddec([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Gauge.dec(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## set_to_current_time
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.set_to_current_time(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Gauge.set_to_current_time(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.set_to_current_time([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Gauge.set_to_current_time(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## track_inprogress
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.track_inprogress(:unknown_metric, fn -> 1 end)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Gauge.track_inprogress(:unknown_metric, fn -> 1 end)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.track_inprogress([name: :metric_with_label, labels: [:l1, :l2]], fn -> 1 end)
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Gauge.track_inprogress(
	+ [name: :metric_with_label, labels: [:l1, :l2]],
	+ fn -> 1 end
	+ )
	+ end

	## set_duration
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.set_duration(:unknown_metric, fn -> 1 end)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Gauge.set_duration(:unknown_metric, fn -> 1 end)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.set_duration([name: :metric_with_label, labels: [:l1, :l2]], fn -> 1 end)
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Gauge.set_duration(
	+ [name: :metric_with_label, labels: [:l1, :l2]],
	+ fn -> 1 end
	+ )
	+ end

	## remove
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.remove(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Gauge.remove(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.remove([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Gauge.remove(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## reset
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.reset(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Gauge.reset(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.reset([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Gauge.reset(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## value
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Gauge.value(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Gauge.value(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Gauge.value([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Gauge.value(name: :metric_with_label, labels: [:l1, :l2])
	+ end
	end

	test "set" do
	- spec = [name: :metric_with_label,
	- labels: [:label],
	- help: ""]
	+ spec = [name: :metric_with_label, labels: [:label], help: ""]
	Gauge.declare(spec)

	Gauge.set(spec, 100)
	assert 100 == Gauge.value(spec)

	Gauge.set(spec, 105)
	assert 105 == Gauge.value(spec)

	Gauge.reset(spec)
	assert 0 == Gauge.value(spec)
	-
	end

	test "inc" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	Gauge.new(spec)

	Gauge.inc(spec)
	Gauge.inc(spec, 3)
	- assert 4 == Gauge.value(spec)
	-
	- Gauge.reset(spec)
	-
	- assert 0 == Gauge.value(spec)
	- end
	-
	- test "dinc" do
	- spec = [name: :http_requests_total,
	- help: ""]
	- Gauge.new(spec)
	-
	- Gauge.dinc(spec)
	- Gauge.dinc(spec, 3.5)
	-
	- ## dinc is async. let's make sure gen_server processed our request
	- Process.sleep(10)
	- assert 4.5 == Gauge.value(spec)
	+ Gauge.inc(spec)
	+ Gauge.inc(spec, 3.5)
	+ assert 8.5 == Gauge.value(spec)

	Gauge.reset(spec)

	assert 0 == Gauge.value(spec)
	end

	test "dec" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	Gauge.new(spec)

	Gauge.dec(spec)
	Gauge.dec(spec, 3)
	- assert (-4 == Gauge.value(spec))
	-
	- Gauge.reset(spec)
	-
	- assert 0 == Gauge.value(spec)
	- end
	-
	- test "ddec" do
	- spec = [name: :http_requests_total,
	- help: ""]
	- Gauge.new(spec)
	-
	- Gauge.ddec(spec)
	- Gauge.ddec(spec, 3.5)
	+ Gauge.dec(spec)
	+ Gauge.dec(spec, 3.5)

	- ## ddec is async. let's make sure gen_server processed our request
	- Process.sleep(10)
	- assert (-4.5 == Gauge.value(spec))
	+ assert -8.5 == Gauge.value(spec)

	Gauge.reset(spec)

	assert 0 == Gauge.value(spec)
	end

	test "set_to_current_time" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	Gauge.new(spec)

	Gauge.set_to_current_time(spec)

	assert :os.system_time(:seconds) == Gauge.value(spec)
	end

	test "test_track_inprogress fn" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	Gauge.new(spec)

	- assert 1 == Gauge.track_inprogress(spec, fn ->
	- Gauge.value(spec)
	- end)
	+ assert 1 ==
	+ Gauge.track_inprogress(spec, fn ->
	+ Gauge.value(spec)
	+ end)

	assert_raise ErlangError, fn ->
	Gauge.track_inprogress(spec, fn ->
	:erlang.error({:qwe})
	end)
	end

	assert 0 = Gauge.value(spec)
	end

	test "test_track_inprogress block" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	Gauge.new(spec)

	assert 1 == Gauge.track_inprogress(spec, do: Gauge.value(spec))

	assert_raise ErlangError, fn ->
	Gauge.track_inprogress spec do
	:erlang.error({:qwe})
	end
	end

	assert 0 = Gauge.value(spec)
	end

	test "set_duration fn" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: "",
	- duration_unit: :seconds]
	+ spec = [
	+ name: :http_requests_total,
	+ labels: [:method],
	+ help: "",
	+ duration_unit: :seconds
	+ ]
	+
	Gauge.new(spec)

	- assert 1 == Gauge.set_duration(spec, fn ->
	- Process.sleep(1000)
	- 1
	- end)
	+ assert 1 ==
	+ Gauge.set_duration(spec, fn ->
	+ Process.sleep(1000)
	+ 1
	+ end)

	assert 1 < Gauge.value(spec) and Gauge.value(spec) < 1.2

	assert_raise ErlangError, fn ->
	Gauge.set_duration(spec, fn ->
	:erlang.error({:qwe})
	end)
	end

	assert 0.0 < Gauge.value(spec) and Gauge.value(spec) < 0.2
	end

	test "set_duration block" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: "",
	- duration_unit: :seconds]
	+ spec = [
	+ name: :http_requests_total,
	+ labels: [:method],
	+ help: "",
	+ duration_unit: :seconds
	+ ]
	+
	Gauge.new(spec)

	assert :ok == Gauge.set_duration(spec, do: Process.sleep(1000))

	assert 1 < Gauge.value(spec) and Gauge.value(spec) < 1.2

	assert_raise ErlangError, fn ->
	Gauge.set_duration spec do
	:erlang.error({:qwe})
	end
	end

	assert 0.0 < Gauge.value(spec) and Gauge.value(spec) < 0.2
	end

	test "remove" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	- wl_spec = [name: :simple_gauge,
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	+ wl_spec = [name: :simple_gauge, help: ""]

	Gauge.new(spec)
	Gauge.new(wl_spec)

	Gauge.inc(spec)
	Gauge.inc(wl_spec)

	assert 1 == Gauge.value(spec)
	assert 1 == Gauge.value(wl_spec)

	assert true == Gauge.remove(spec)
	assert true == Gauge.remove(wl_spec)

	assert :undefined == Gauge.value(spec)
	assert :undefined == Gauge.value(wl_spec)

	assert false == Gauge.remove(spec)
	assert false == Gauge.remove(wl_spec)
	end

	test "default value" do
	- lspec = [name: :http_requests_gauge,
	- labels: [:method],
	- help: ""]
	+ lspec = [name: :http_requests_gauge, labels: [:method], help: ""]
	Gauge.new(lspec)

	assert :undefined == Gauge.value(lspec)

	- spec = [name: :something_gauge,
	- labels: [],
	- help: ""]
	+ spec = [name: :something_gauge, labels: [], help: ""]
	Gauge.new(spec)

	assert 0 == Gauge.value(spec)
	end
	-
	end
	diff --git a/test/metric/histogram_test.exs b/test/metric/histogram_test.exs
	index 739ac8b..5631bd2 100644
	--- a/test/metric/histogram_test.exs
	+++ b/test/metric/histogram_test.exs
	@@ -1,318 +1,270 @@
	defmodule Prometheus.HistogramTest do
	use Prometheus.Case

	test "registration" do
	- spec = [name: :name,
	- help: "",
	- registry: :qwe]
	+ spec = [name: :name, help: "", registry: :qwe]

	assert true == Histogram.declare(spec)
	assert false == Histogram.declare(spec)
	- assert_raise Prometheus.MFAlreadyExistsError,
	- "Metric qwe:name already exists.",
	- fn ->
	+
	+ assert_raise Prometheus.MFAlreadyExistsError, "Metric qwe:name already exists.", fn ->
	Histogram.new(spec)
	end
	end

	test "spec errors" do
	assert_raise Prometheus.MissingMetricSpecKeyError,
	- "Required key name is missing from metric spec.",
	- fn ->
	- Histogram.new([help: ""])
	- end
	- assert_raise Prometheus.InvalidMetricNameError,
	- "Invalid metric name: 12.",
	- fn ->
	- Histogram.new([name: 12, help: ""])
	+ "Required key name is missing from metric spec.",
	+ fn ->
	+ Histogram.new(help: "")
	+ end
	+
	+ assert_raise Prometheus.InvalidMetricNameError, "Invalid metric name: 12.", fn ->
	+ Histogram.new(name: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricLabelsError,
	- "Invalid metric labels: 12.",
	- fn ->
	- Histogram.new([name: "qwe", labels: 12, help: ""])
	+
	+ assert_raise Prometheus.InvalidMetricLabelsError, "Invalid metric labels: 12.", fn ->
	+ Histogram.new(name: "qwe", labels: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricHelpError,
	- "Invalid metric help: 12.",
	- fn ->
	- Histogram.new([name: "qwe", help: 12])
	+
	+ assert_raise Prometheus.InvalidMetricHelpError, "Invalid metric help: 12.", fn ->
	+ Histogram.new(name: "qwe", help: 12)
	end
	+
	assert_raise Prometheus.InvalidLabelNameError,
	- "Invalid label name: le (histogram cannot have a label named \"le\").",
	- fn ->
	- Histogram.new([name: "qwe", help: "", labels: ["le"]])
	- end
	+ "Invalid label name: le (histogram cannot have a label named \"le\").",
	+ fn ->
	+ Histogram.new(name: "qwe", help: "", labels: ["le"])
	+ end
	+
	## buckets
	- assert_raise Prometheus.HistogramNoBucketsError,
	- "Invalid histogram buckets: .",
	- fn ->
	- Histogram.new([name: "qwe", help: "", buckets: []])
	- end
	- assert_raise Prometheus.HistogramNoBucketsError,
	- "Invalid histogram buckets: undefined.",
	- fn ->
	- Histogram.new([name: "qwe", help: "", buckets: :undefined])
	- end
	- assert_raise Prometheus.HistogramInvalidBucketsError,
	- "Invalid histogram buckets: 1 (not a list).",
	- fn ->
	- Histogram.new([name: "qwe", help: "", buckets: 1])
	- end
	- assert_raise Prometheus.HistogramInvalidBucketsError,
	- "Invalid histogram buckets: [1,3,2] (buckets not sorted).",
	- fn ->
	- Histogram.new([name: "qwe", help: "", buckets: [1, 3, 2]])
	- end
	- assert_raise Prometheus.HistogramInvalidBoundError,
	- "Invalid histogram bound: qwe.",
	- fn ->
	- Histogram.new([name: "qwe", help: "", buckets: ["qwe"]])
	+ assert_raise Prometheus.NoBucketsError, "Invalid histogram buckets: .", fn ->
	+ Histogram.new(name: "qwe", help: "", buckets: [])
	end
	+
	+ assert_raise Prometheus.NoBucketsError,
	+ "Invalid histogram buckets: undefined.",
	+ fn ->
	+ Histogram.new(name: "qwe", help: "", buckets: :undefined)
	+ end
	+
	+ assert_raise Prometheus.InvalidBucketsError,
	+ "Invalid histogram buckets: 1 (not a list).",
	+ fn ->
	+ Histogram.new(name: "qwe", help: "", buckets: 1)
	+ end
	+
	+ assert_raise Prometheus.InvalidBucketsError,
	+ "Invalid histogram buckets: [1,3,2] (buckets not sorted).",
	+ fn ->
	+ Histogram.new(name: "qwe", help: "", buckets: [1, 3, 2])
	+ end
	+
	+ assert_raise Prometheus.InvalidBoundError,
	+ "Invalid histogram bound: qwe.",
	+ fn ->
	+ Histogram.new(name: "qwe", help: "", buckets: ["qwe"])
	+ end
	end

	test "histogram specific errors" do
	- spec = [name: :http_requests_total,
	- help: ""]
	+ spec = [name: :http_requests_total, help: ""]

	## observe
	assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (observe accepts only integers).",
	- fn ->
	- Histogram.observe(spec, "qwe")
	- end
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: 1.5 (observe accepts only integers).",
	- fn ->
	- Histogram.observe(spec, 1.5)
	- end
	-
	- ## dobserve
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (dobserve accepts only numbers).",
	- fn ->
	- Histogram.dobserve(spec, "qwe")
	- end
	+ "Invalid value: \"qwe\" (observe accepts only numbers).",
	+ fn ->
	+ Histogram.observe(spec, "qwe")
	+ end
	end

	test "mf/arity errors" do
	- spec = [name: :metric_with_label,
	- labels: [:label],
	- help: ""]
	+ spec = [name: :metric_with_label, labels: [:label], help: ""]
	Histogram.declare(spec)

	## observe
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Histogram.observe(:unknown_metric, 1)
	- end
	- assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Histogram.observe([name: :metric_with_label, labels: [:l1, :l2]], 1)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Histogram.observe(:unknown_metric, 1)
	+ end

	- ## dobserve
	- assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Histogram.dobserve(:unknown_metric)
	- end
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Histogram.dobserve([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Histogram.observe([name: :metric_with_label, labels: [:l1, :l2]], 1)
	+ end

	## observe_duration
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Histogram.observe_duration(:unknown_metric, fn -> 1 end)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Histogram.observe_duration(:unknown_metric, fn -> 1 end)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Histogram.observe_duration(
	- [name: :metric_with_label, labels: [:l1, :l2]], fn -> 1 end)
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Histogram.observe_duration(
	+ [name: :metric_with_label, labels: [:l1, :l2]],
	+ fn -> 1 end
	+ )
	+ end

	## remove
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Histogram.remove(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Histogram.remove(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Histogram.remove([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Histogram.remove(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## reset
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Histogram.reset(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Histogram.reset(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Histogram.reset([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Histogram.reset(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## value
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Histogram.value(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Histogram.value(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Histogram.value([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Histogram.value(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## observe_duration
	assert_raise Prometheus.InvalidBlockArityError,
	- "Fn with arity 2 (args: :x, :y) passed as block.",
	- fn ->
	- Macro.expand(quote do
	- Histogram.observe_duration(spec, fn(x, y) -> 1 + x + y end)
	- end, __ENV__)
	- end
	+ "Fn with arity 2 (args: :x, :y) passed as block.",
	+ fn ->
	+ Macro.expand(
	+ quote do
	+ Histogram.observe_duration(spec, fn x, y -> 1 + x + y end)
	+ end,
	+ __ENV__
	+ )
	+ end
	end

	test "observe" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	Histogram.new(spec)

	Histogram.observe(spec)
	Histogram.observe(spec, 3)
	- assert {[0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0], 4} == Histogram.value(spec)
	-
	- Histogram.reset(spec)
	-
	- assert {[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], 0} == Histogram.value(spec)
	- end
	-
	- test "dobserve" do
	- spec = [name: :http_requests_total,
	- help: ""]
	- Histogram.new(spec)
	-
	- Histogram.dobserve(spec)
	- Histogram.dobserve(spec, 3.5)
	+ Histogram.observe(spec)
	+ Histogram.observe(spec, 3.5)

	- ## dobserve is async. let's make sure gen_server processed our request
	- Process.sleep(10)
	- assert {[0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0], 4.5} == Histogram.value(spec)
	+ assert {[0, 0, 0, 0, 0, 0, 0, 2, 0, 2, 0, 0], 8.5} == Histogram.value(spec)

	Histogram.reset(spec)

	assert {[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], 0} == Histogram.value(spec)
	end

	test "observe_duration fn" do
	- spec = [name: :duration_seconds,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :duration_seconds, labels: [:method], help: ""]
	Histogram.new(spec)

	- assert 1 == Histogram.observe_duration(spec, fn ->
	- Process.sleep(1000)
	- 1
	- end)
	+ assert 1 ==
	+ Histogram.observe_duration(spec, fn ->
	+ Process.sleep(1000)
	+ 1
	+ end)

	## observe_duration is async. let's make sure gen_server processed our request
	Process.sleep(10)
	{buckets, sum} = Histogram.value(spec)
	assert [0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0] == buckets
	assert 1 < sum and sum < 1.2

	assert_raise ErlangError, fn ->
	Histogram.observe_duration(spec, fn ->
	:erlang.error({:qwe})
	end)
	end

	## observe_duration is async. let's make sure gen_server processed our request
	Process.sleep(10)
	{buckets, sum} = Histogram.value(spec)
	assert [1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0] == buckets
	assert 1 < sum and sum < 1.2
	end

	test "observe_duration block" do
	- spec = [name: :duration_seconds,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :duration_seconds, labels: [:method], help: ""]
	Histogram.new(spec)

	assert :ok == Histogram.observe_duration(spec, do: Process.sleep(1000))

	## observe_duration is async. let's make sure gen_server processed our request
	Process.sleep(10)
	{buckets, sum} = Histogram.value(spec)
	assert [0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0] == buckets
	assert 1 < sum and sum < 1.2

	assert_raise ErlangError, fn ->
	Histogram.observe_duration spec do
	:erlang.error({:qwe})
	end
	end

	## observe_duration is async. let's make sure gen_server processed our request
	Process.sleep(10)
	{buckets, sum} = Histogram.value(spec)
	assert [1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0] == buckets
	assert 1 < sum and sum < 1.2
	end

	test "remove" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	- wl_spec = [name: :simple_histogram,
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	+ wl_spec = [name: :simple_histogram, help: ""]

	Histogram.new(spec)
	Histogram.new(wl_spec)

	Histogram.observe(spec)
	Histogram.observe(wl_spec)

	assert {[0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0], 1} == Histogram.value(spec)
	assert {[0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0], 1} == Histogram.value(wl_spec)

	assert true == Histogram.remove(spec)
	assert true == Histogram.remove(wl_spec)

	assert :undefined == Histogram.value(spec)
	assert :undefined == Histogram.value(wl_spec)

	assert false == Histogram.remove(spec)
	assert false == Histogram.remove(wl_spec)
	end

	test "undefined value" do
	- lspec = [name: :duraiton_histogram,
	- labels: [:method],
	- buckets: [5, 10],
	- help: ""]
	+ lspec = [name: :duraiton_histogram, labels: [:method], buckets: [5, 10], help: ""]
	Histogram.new(lspec)

	assert :undefined == Histogram.value(lspec)

	- spec = [name: :something_histogram,
	- labels: [],
	- buckets: [5, 10],
	- help: ""]
	+ spec = [name: :something_histogram, labels: [], buckets: [5, 10], help: ""]
	Histogram.new(spec)

	assert {[0, 0, 0], 0} == Histogram.value(spec)
	end
	-
	end
	diff --git a/test/metric/summary_test.exs b/test/metric/summary_test.exs
	index c01e3aa..34475c0 100644
	--- a/test/metric/summary_test.exs
	+++ b/test/metric/summary_test.exs
	@@ -1,290 +1,241 @@
	defmodule Prometheus.SummaryTest do
	use Prometheus.Case

	test "registration" do
	- spec = [name: :name,
	- help: "",
	- registry: :qwe]
	+ spec = [name: :name, help: "", registry: :qwe]

	assert true == Summary.declare(spec)
	assert false == Summary.declare(spec)
	- assert_raise Prometheus.MFAlreadyExistsError,
	- "Metric qwe:name already exists.",
	- fn ->
	+
	+ assert_raise Prometheus.MFAlreadyExistsError, "Metric qwe:name already exists.", fn ->
	Summary.new(spec)
	end
	end

	test "spec errors" do
	assert_raise Prometheus.MissingMetricSpecKeyError,
	- "Required key name is missing from metric spec.",
	- fn ->
	- Summary.new([help: ""])
	- end
	- assert_raise Prometheus.InvalidMetricNameError,
	- "Invalid metric name: 12.",
	- fn ->
	- Summary.new([name: 12, help: ""])
	+ "Required key name is missing from metric spec.",
	+ fn ->
	+ Summary.new(help: "")
	+ end
	+
	+ assert_raise Prometheus.InvalidMetricNameError, "Invalid metric name: 12.", fn ->
	+ Summary.new(name: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricLabelsError,
	- "Invalid metric labels: 12.",
	- fn ->
	- Summary.new([name: "qwe", labels: 12, help: ""])
	+
	+ assert_raise Prometheus.InvalidMetricLabelsError, "Invalid metric labels: 12.", fn ->
	+ Summary.new(name: "qwe", labels: 12, help: "")
	end
	- assert_raise Prometheus.InvalidMetricHelpError,
	- "Invalid metric help: 12.",
	- fn ->
	- Summary.new([name: "qwe", help: 12])
	+
	+ assert_raise Prometheus.InvalidMetricHelpError, "Invalid metric help: 12.", fn ->
	+ Summary.new(name: "qwe", help: 12)
	end
	+
	assert_raise Prometheus.InvalidLabelNameError,
	- "Invalid label name: quantile (summary cannot have a label named \"quantile\").",
	- fn ->
	- Summary.new([name: "qwe", help: "", labels: ["quantile"]])
	- end
	+ "Invalid label name: quantile (summary cannot have a label named \"quantile\").",
	+ fn ->
	+ Summary.new(name: "qwe", help: "", labels: ["quantile"])
	+ end
	end

	test "summary specific errors" do
	- spec = [name: :http_requests_total,
	- help: ""]
	+ spec = [name: :http_requests_total, help: ""]

	## observe
	assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (observe accepts only integers).",
	- fn ->
	- Summary.observe(spec, "qwe")
	- end
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: 1.5 (observe accepts only integers).",
	- fn ->
	- Summary.observe(spec, 1.5)
	- end
	-
	- ## dobserve
	- assert_raise Prometheus.InvalidValueError,
	- "Invalid value: \"qwe\" (dobserve accepts only numbers).",
	- fn ->
	- Summary.dobserve(spec, "qwe")
	- end
	+ "Invalid value: \"qwe\" (observe accepts only numbers).",
	+ fn ->
	+ Summary.observe(spec, "qwe")
	+ end

	## observe_duration TODO: assert_compile_time_raise
	assert_raise Prometheus.InvalidBlockArityError,
	- "Fn with arity 2 (args: :x, :y) passed as block.",
	- fn ->
	- Macro.expand(quote do
	- Summary.observe_duration(spec, fn(x, y) -> 1 + x + y end)
	- end, __ENV__)
	- end
	+ "Fn with arity 2 (args: :x, :y) passed as block.",
	+ fn ->
	+ Macro.expand(
	+ quote do
	+ Summary.observe_duration(spec, fn x, y -> 1 + x + y end)
	+ end,
	+ __ENV__
	+ )
	+ end
	end

	test "mf/arity errors" do
	- spec = [name: :metric_with_label,
	- labels: [:label],
	- help: ""]
	+ spec = [name: :metric_with_label, labels: [:label], help: ""]
	Summary.declare(spec)

	## observe
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Summary.observe(:unknown_metric, 1)
	- end
	- assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Summary.observe([name: :metric_with_label, labels: [:l1, :l2]], 1)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Summary.observe(:unknown_metric, 1)
	+ end

	- ## dobserve
	- assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Summary.dobserve(:unknown_metric)
	- end
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Summary.dobserve([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Summary.observe([name: :metric_with_label, labels: [:l1, :l2]], 1)
	+ end

	## observe_duration
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Summary.observe_duration(:unknown_metric, fn -> 1 end)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Summary.observe_duration(:unknown_metric, fn -> 1 end)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Summary.observe_duration(
	- [name: :metric_with_label, labels: [:l1, :l2]], fn -> 1 end)
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Summary.observe_duration(
	+ [name: :metric_with_label, labels: [:l1, :l2]],
	+ fn -> 1 end
	+ )
	+ end

	## remove
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Summary.remove(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Summary.remove(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Summary.remove([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Summary.remove(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## reset
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Summary.reset(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Summary.reset(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Summary.reset([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Summary.reset(name: :metric_with_label, labels: [:l1, :l2])
	+ end

	## value
	assert_raise Prometheus.UnknownMetricError,
	- "Unknown metric {registry: default, name: unknown_metric}.",
	- fn ->
	- Summary.value(:unknown_metric)
	- end
	+ "Unknown metric {registry: default, name: unknown_metric}.",
	+ fn ->
	+ Summary.value(:unknown_metric)
	+ end
	+
	assert_raise Prometheus.InvalidMetricArityError,
	- "Invalid metric arity: got 2, expected 1.",
	- fn ->
	- Summary.value([name: :metric_with_label, labels: [:l1, :l2]])
	- end
	+ "Invalid metric arity: got 2, expected 1.",
	+ fn ->
	+ Summary.value(name: :metric_with_label, labels: [:l1, :l2])
	+ end
	end

	test "observe" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	Summary.new(spec)

	Summary.observe(spec)
	Summary.observe(spec, 3)
	- assert {2, 4} == Summary.value(spec)
	-
	- Summary.reset(spec)
	-
	- assert {0, 0} == Summary.value(spec)
	- end
	-
	- test "dobserve" do
	- spec = [name: :http_requests_total,
	- help: ""]
	- Summary.new(spec)
	+ Summary.observe(spec)
	+ Summary.observe(spec, 3.5)

	- Summary.dobserve(spec)
	- Summary.dobserve(spec, 3.5)
	-
	- ## dobserve is async. let's make sure gen_server processed our increment request
	- Process.sleep(10)
	- assert {2, 4.5} == Summary.value(spec)
	+ assert {4, 8.5} == Summary.value(spec)

	Summary.reset(spec)

	assert {0, 0} == Summary.value(spec)
	end

	test "observe_duration fn" do
	- spec = [name: :duration_seconds,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :duration_seconds, labels: [:method], help: ""]
	Summary.new(spec)

	- assert 1 == Summary.observe_duration(spec, fn ->
	- Process.sleep(1000)
	- 1
	- end)
	+ assert 1 ==
	+ Summary.observe_duration(spec, fn ->
	+ Process.sleep(1000)
	+ 1
	+ end)

	## observe_duration is async. let's make sure gen_server processed our request
	Process.sleep(10)
	{count, sum} = Summary.value(spec)
	assert 1 == count
	assert 1 < sum and sum < 1.2

	assert_raise ErlangError, fn ->
	Summary.observe_duration(spec, fn ->
	:erlang.error({:qwe})
	end)
	end

	## observe_duration is async. let's make sure gen_server processed our request
	Process.sleep(10)
	{count, sum} = Summary.value(spec)
	assert 2 == count
	assert 1 < sum and sum < 1.2
	end

	test "observe_duration block" do
	- spec = [name: :duration_seconds,
	- labels: [:method],
	- help: ""]
	+ spec = [name: :duration_seconds, labels: [:method], help: ""]
	Summary.new(spec)

	assert :ok == Summary.observe_duration(spec, do: Process.sleep(1000))

	## observe_duration is async. let's make sure gen_server processed our request
	Process.sleep(10)
	{count, sum} = Summary.value(spec)
	assert 1 == count
	assert 1 < sum and sum < 1.2

	assert_raise ErlangError, fn ->
	Summary.observe_duration spec do
	:erlang.error({:qwe})
	end
	end

	## observe_duration is async. let's make sure gen_server processed our request
	Process.sleep(10)
	{count, sum} = Summary.value(spec)
	assert 2 == count
	assert 1 < sum and sum < 1.2
	end

	test "remove" do
	- spec = [name: :http_requests_total,
	- labels: [:method],
	- help: ""]
	- wl_spec = [name: :simple_summary,
	- help: ""]
	+ spec = [name: :http_requests_total, labels: [:method], help: ""]
	+ wl_spec = [name: :simple_summary, help: ""]

	Summary.new(spec)
	Summary.new(wl_spec)

	Summary.observe(spec)
	Summary.observe(wl_spec)

	assert {1, 1} == Summary.value(spec)
	assert {1, 1} == Summary.value(wl_spec)

	assert true == Summary.remove(spec)
	assert true == Summary.remove(wl_spec)

	assert :undefined == Summary.value(spec)
	assert :undefined == Summary.value(wl_spec)

	assert false == Summary.remove(spec)
	assert false == Summary.remove(wl_spec)
	end

	test "undefined value" do
	- lspec = [name: :orders_summary,
	- labels: [:department],
	- help: ""]
	+ lspec = [name: :orders_summary, labels: [:department], help: ""]
	Summary.new(lspec)

	assert :undefined == Summary.value(lspec)

	- spec = [name: :something_summary,
	- labels: [],
	- help: ""]
	+ spec = [name: :something_summary, labels: [], help: ""]
	Summary.new(spec)

	assert {0, 0} == Summary.value(spec)
	end
	-
	end
	diff --git a/test/metric_test.exs b/test/metric_test.exs
	index 5c3ccaa..ef0b410 100644
	--- a/test/metric_test.exs
	+++ b/test/metric_test.exs
	@@ -1,70 +1,81 @@
	defmodule Prometheus.MetricTest do
	use Prometheus.Case

	doctest Prometheus.Metric

	defmacro __before_compile__(_env) do
	quote do
	def injected_fun() do
	1
	end
	end
	end

	test "@metric attributes leads to metric declaration" do
	defmodule ModuleWithMetrics do
	use Prometheus.Metric
	@before_compile Prometheus.MetricTest

	@counter name: :test_counter1, labels: [], help: "qwe"
	@counter name: :test_counter2, labels: [:tag], help: "qwa"

	@gauge name: :test_gauge1, labels: [], help: "qwe"
	@gauge name: :test_gauge2, labels: [:tag], help: "qwa"

	@boolean name: :test_boolean1, labels: [], help: "qwe"
	@boolean name: :test_boolean2, labels: [:tag], help: "qwa"

	@summary name: :test_summary1, labels: [], help: "qwe"
	@summary name: :test_summary2, labels: [:tag], help: "qwa"

	- @histogram name: :test_histogram1, labels: [], buckets: [1, 2], help: "qwe"
	+ @histogram name: :test_histogram1, labels: [], buckets: [1, 2], help: "qwe"
	@histogram name: :test_histogram2, labels: [:tag], buckets: [1, 2], help: "qwa"

	@on_load :custom_on_load_fun

	def custom_on_load_fun() do
	Counter.declare(name: :custom_counter, labels: [], help: "qwe")
	:ok
	end
	end

	defmodule ModuleWithoutOnLoad do
	use Prometheus.Metric

	@counter name: :test_counter3, labels: [], help: "qwe"
	end

	assert 1 == ModuleWithMetrics.injected_fun()

	assert false == Counter.declare(name: :custom_counter, labels: [], help: "qwe")
	assert false == Counter.declare(name: :test_counter3, labels: [], help: "qwe")

	assert false == Counter.declare(name: :test_counter1, labels: [], help: "qwe")
	assert false == Counter.declare(name: :test_counter2, labels: [:tag], help: "qwa")

	assert false == Gauge.declare(name: :test_gauge1, labels: [], help: "qwe")
	assert false == Gauge.declare(name: :test_gauge2, labels: [:tag], help: "qwa")

	assert false == Boolean.declare(name: :test_boolean1, labels: [], help: "qwe")
	assert false == Boolean.declare(name: :test_boolean2, labels: [:tag], help: "qwa")

	assert false == Summary.declare(name: :test_summary1, labels: [], help: "qwe")
	assert false == Summary.declare(name: :test_summary2, labels: [:tag], help: "qwa")

	assert false ==
	- Histogram.declare(name: :test_histogram1, labels: [], buckets: [1, 2], help: "")
	+ Histogram.declare(
	+ name: :test_histogram1,
	+ labels: [],
	+ buckets: [1, 2],
	+ help: ""
	+ )
	+
	assert false ==
	- Histogram.declare(name: :test_histogram2, labels: [:tag], buckets: [1, 2], help: "")
	+ Histogram.declare(
	+ name: :test_histogram2,
	+ labels: [:tag],
	+ buckets: [1, 2],
	+ help: ""
	+ )
	end
	end
	diff --git a/test/model_test.exs b/test/model_test.exs
	index b3b25bc..ff3244e 100644
	--- a/test/model_test.exs
	+++ b/test/model_test.exs
	@@ -1,21 +1,26 @@
	defmodule Prometheus.ModelTest do
	-
	use Prometheus.Case

	require Prometheus.Model

	doctest Prometheus.Model

	def collect_metrics(:pool_size, _) do
	Prometheus.Model.untyped_metric(365)
	end

	test "create_mf" do
	assert {:MetricFamily, <<"pool_size">>, <<"help">>, :UNTYPED,
	- [{:Metric, [], :undefined, :undefined, :undefined,
	- {:Untyped, 365},
	- :undefined, :undefined}]} ==
	- Prometheus.Model.create_mf(
	- :pool_size, "help", :untyped, Prometheus.ModelTest, :undefined)
	+ [
	+ {:Metric, [], :undefined, :undefined, :undefined, {:Untyped, 365},
	+ :undefined, :undefined}
	+ ]} ==
	+ Prometheus.Model.create_mf(
	+ :pool_size,
	+ "help",
	+ :untyped,
	+ Prometheus.ModelTest,
	+ :undefined
	+ )
	end
	end
	diff --git a/test/registry_test.exs b/test/registry_test.exs
	index 0368334..2f61609 100644
	--- a/test/registry_test.exs
	+++ b/test/registry_test.exs
	@@ -1,69 +1,71 @@
	defmodule Prometheus.RegistryTest do
	-
	use Prometheus.Case
	alias Prometheus.Registry
	alias Prometheus.RegistryTest

	import ExUnit.CaptureIO

	def deregister_cleanup(_), do: :ok

	test "registry exists" do
	Prometheus.Registry.register_collector(:test_registry, RegistryTest)

	assert true == Registry.exists(:test_registry)

	assert :test_registry == Registry.exists("test_registry")

	assert false == Registry.exists(:qweqwe)
	assert false == Registry.exists("qweqwe")
	end

	test "default Registry" do
	# default registry
	assert :ok == Prometheus.Registry.register_collector(RegistryTest)
	assert [RegistryTest] == Registry.collectors()
	assert true == Registry.collector_registered?(RegistryTest)
	Registry.clear()
	assert [] == Registry.collectors()
	assert false == Registry.collector_registered?(RegistryTest)

	assert :ok == Registry.register_collector(RegistryTest)
	Registry.deregister_collector(RegistryTest)
	assert [] == Registry.collectors()
	assert false == Registry.collector_registered?(RegistryTest)

	## custom registry
	assert :ok == Registry.register_collector(:custom_collector, RegistryTest)
	assert [RegistryTest] == Registry.collectors(:custom_collector)
	assert true == Registry.collector_registered?(:custom_collector, RegistryTest)
	Registry.clear(:custom_collector)
	assert [] == Registry.collectors(:custom_collector)
	assert false == Registry.collector_registered?(:custom_collector, RegistryTest)

	assert :ok == Registry.register_collector(:custom_collector, RegistryTest)
	Registry.deregister_collector(:custom_collector, RegistryTest)
	assert [] == Registry.collectors(:custom_collector)
	assert false == Registry.collector_registered?(:custom_collector, RegistryTest)

	## register_collectors && collect; default registry
	assert :ok == Registry.register_collectors([RegistryTest])
	assert [RegistryTest] == Registry.collectors()
	+
	assert capture_io(fn ->
	- Registry.collect(fn (:default, collector) ->
	- :io.format("~p", [collector])
	- end) ==
	- "Elixir.RegistryTest"
	- end)
	+ Registry.collect(fn :default, collector ->
	+ :io.format("~p", [collector])
	+ end) == "Elixir.RegistryTest"
	+ end)

	## register_collectors && collect; custom registry
	assert :ok == Registry.register_collectors(:custom_collector, [RegistryTest])
	assert [RegistryTest] == Registry.collectors(:custom_collector)
	+
	assert capture_io(fn ->
	- Registry.collect(fn (:custom_collector, collector) ->
	- :io.format("~p", [collector])
	- end, :custom_collector) ==
	- "Elixir.RegistryTest"
	- end)
	+ Registry.collect(
	+ fn :custom_collector, collector ->
	+ :io.format("~p", [collector])
	+ end,
	+ :custom_collector
	+ ) == "Elixir.RegistryTest"
	+ end)
	end
	end
	diff --git a/test/test_helper.exs b/test/test_helper.exs
	index d8b7989..a054dfa 100644
	--- a/test/test_helper.exs
	+++ b/test/test_helper.exs
	@@ -1,25 +1,23 @@
	ExUnit.start()

	defmodule Prometheus.Case do
	defmacro __using__(_opts) do
	quote do
	-
	use ExUnit.Case
	use Prometheus
	import ExUnit.CaptureIO

	setup do
	collectors = Prometheus.Registry.collectors()
	Prometheus.Registry.clear()
	Prometheus.Registry.clear(:qwe)

	- on_exit fn ->
	+ on_exit(fn ->
	Prometheus.Registry.clear()
	Prometheus.Registry.clear(:qwe)
	Prometheus.Registry.register_collectors(collectors)
	- end
	+ end)
	end
	-
	end
	end
	end

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