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Property-based testing for Elixir (QuickCheck style). It uses Erlang's triq library for underlying checking engine, and ExCheck's modules provide wrapper macros for ExUnit tests.
First add ExCheck and triq to your project's dependencies in mix.exs.
defp deps do [ {:excheck, "~> 0.6", only: :test} ] end
You need to have erlang-eunit installed in order to build triq.
and add the following to test_helper.exs:
ExCheck.start # ... other helper functions ExUnit.start
You can also specify the amount of tests that you want to run for each property by adding the following to your config.exs:
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
The following is an testing example. ExCheck.SampleTest is the testing code for ExCheck.Sample.
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 skip samples that does not satisfy the predicate. Also, it prints x when skip a sample 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 # specify iteration count for running test @tag iterations: 30 property :square_with_iteration_count do for_all x in int(), do: x * x >= 0 end end
defmodule ExCheck.Sample do @moduledoc """ Sample logic to be tested by ExCheck (refer to sample_test.exs for tests) """ @doc "concatenate 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
mix test test/sample_test.exs ..................................................................................................................................................................................................................xxx....x.xx..xxx.x.xx.xx..x...x..x..xx.xx..xx.xx.x..x.x..x..x......x.xx............x.x..x..x...xxx..x..x..xx.x..xx.xx.x......x.xxx.xx..xx.x.x.x.xx.x.xx......xx..xxxx..x....xxx.xxxxx.xxxxx..xx........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................... Finished in 0.2 seconds (0.1s on load, 0.08s on tests) 948 tests, 0 failures
You can also add the optional flag --trace to get additional output
mix test test/sample_test.exs --trace ExCheck.SampleTest * implies_property........xx.x.x..x..xx.xxx..x.x.x.x..x..x..xx....x.x.xx.xxxxxx..xx...x...xx.x...x.x..xxxxx..x...x......xxxxx.x.x..xxx.x..x.xx..xx..xxxx.x.x..xx.......x..xx.xx...x...x...xxx.xxx.x.xx.xx * implies_property (14.7ms) * square_property........................................................................................................................................................................................ * square_property (4.1ms) * push_list_property..................................................................................................................................................................................... * push_list_property (14.7ms) * square_with_iteration_count_property (0.7ms)...................... * such_that_property..................................................................................................................................................................................... * such_that_property (4.8ms) * concat_list_property................................................................................................................................................................................... * concat_list_property (25.4ms) Finished in 0.1 seconds (0.1s on load, 0.06s on tests) 942 tests, 0 failures
There are some more examples at test directory.
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
- It's a trial implementation, and has limited functionalities yet.
- Files in test folder contains some more property examples.