# ExCheck [](http://travis-ci.org/parroty/excheck) [](https://coveralls.io/r/parroty/excheck)
Property-based testing for Elixir (QuickCheck style).
It uses Erlang's [triq](https://github.com/krestenkrab/triq) library for underlying checking engine, and ExCheck's modules provide wrapper macros for ExUnit tests.
### Installation
First add ExCheck and triq to your project's dependencies in mix.exs.
```Elixir
defp deps do
[
{:excheck, "~> 0.3", only: :test},
{:triq, github: "krestenkrab/triq", only: :test}
]
end
```
and add the following to test_helpers.exs:
```Elixir
ExCheck.start
# ... other helper functions
ExUnit.start
```
### Configuration
You can also specify the amount of tests that you want to run for each property
by adding the following to your config.exs:
```Elixir
use Mix.Config
# import "#{Mix.env}.exs" # If you want to specify different amount for each environment
# And then in this file (or different amount in each config file):
config :excheck, :number_iterations, 200
```
**Note:** This setting is not effective for `ExCheck.check(module_name)` at the moment (refer to [#13](https://github.com/parroty/excheck/pull/13)).
### Usage
The following is an testing example. `ExCheck.SampleTest` is the testing code for `ExCheck.Sample`.
#### Test
```Elixir
defmodule ExCheck.SampleTest do
use ExUnit.Case, async: false
use ExCheck
alias ExCheck.Sample
property :square do
for_all x in int, do: x * x >= 0
end
property :implies do
for_all x in int do
implies x >= 0 do
x >= 0
end
end
end
property :such_that do
for_all {x, y} in such_that({xx, yy} in {int, int} when xx < yy) do
x < y
end
end
property :concat_list do
for_all {xs, ys} in {list(int), list(int)} do
Enum.count(Sample.concat(xs, ys)) == Enum.count(xs) + Enum.count(ys)
end
end
property :push_list do
for_all {x, y} in {int, list(int)} do
result = Sample.push(x, y)
Enum.at(result, 0) == x and Enum.count(result) == Enum.count(y) + 1
end
end
end
```
#### Code
```Elixir
defmodule ExCheck.Sample do
@moduledoc """
Sample logic to be tested by ExCheck (refer to sample_test.exs for tests)
"""
@doc "concatinate the list"
def concat(x, y) do
x ++ y
end
@doc "push element in the list"
def push(x, y) do
[x|y]
end
end
```
#### Run
```Shell
$ MIX_ENV=test mix test test/sample_test.exs
.............................................................................................
Ran 100 tests
....x.....xx.x.xxxx.xxxx...xxxx...xx.xxxx...x.....x.x.xx...xx.x...xxx..x...xx..xxxxx..xxxx...
Ran 50 tests
.............................................................................................
Ran 100 tests
.............................................................................................
Ran 100 tests
.............................................................................................
Ran 100 tests
.
Finished in 0.2 seconds (0.1s on load, 0.03s on tests)
5 tests, 0 failures
```
There are some more examples at <a href="https://github.com/parroty/excheck/tree/master/test" target="_blank">test</a> directory.
### Generators
The following generators defined in :triq are imported through "use ExCheck" statement.
- list/1, tuple/1, int/0, int/1, int/2, byte/0, real/0, sized/1, elements/1, any/0, atom/0, atom/1, choose/2, oneof/1, frequency/1, bool/0, char/0, return/1, vector/2, binary/1, binary/0, non_empty/1, resize/2, non_neg_integer/0, pos_integer/0,
- unicode_char/0, unicode_string/0, unicode_string/1, unicode_binary/0, unicode_binary/1, unicode_binary/2, unicode_characters/0, unicode_characters/1,
- bind/2, bindshrink/2, suchthat/2, pick/2, shrink/2, sample/1, sampleshrink/1, seal/1, open/1, peek/1, domain/3, shrink_without_duplicates/1
### Notes
- It's a trial implementation, and has limited functionalities yet.
- Files in test folder contains some more property examples.
