rtypes_propcheck

The library implements a PropCheck generator backend for the RTypes library.

Usage

Let's suppose you defined a type and you have a function f/1 which takes a value of that type and returns a value of some other type

defmodule MyModule do
  @type foo :: %{key1: integer(), key2: Keyword.t()}
  @type goo :: 1..512

  @spec f(foo) :: goo
  def f(a_foo) do
    # ...
  end
end

Now, you want to write a property to ensure that your function is total, that is, for any value that belongs to type foo you expect the function to return a value of type goo.

You can achieve this as follows

defmodule MyTest do
  use PropCheck
  use ExUnit.Case
  require RTypes.Generator, as Generator
  require RTypes

  property "f(foo) always returns goo" do
    gen = Generator.make(MyModule.foo(), Generator.PropCheck)
    goo? = RTypes.make_predicate(MyModule.goo())

    forall value <- gen() do
      goo?.(MyModule.f(value))
    end
  end
end

See test/rtypes_propcheck_test.exs for some examples.