Tracee

This Elixir library offers functionality to trace and assert expected function calls within concurrent Elixir processes.

This allows you to ensure that destructive and/or expensive functions are only called the expected number of times. For more information, see the Elixir forum post that motivated the development of this library.

Installation

Just add tracee to your list of dependencies in mix.exs:

def deps do
  [
    {:tracee, "~> 0.2.0", only: :test}
  ]
end

Usage

defmodule ModuleTest do
  use ExUnit.Case

  import Tracee

  setup :verify_on_exit!

  describe "fun/0" do
    test "calls expensive function only once" do
      expect(AnotherModule, :expensive_fun, 1)

      assert Module.fun()
    end

    test "calls expensive function only once from another process" do
      expect(AnotherModule, :expensive_fun, 1)

      assert fn -> Module.fun() end
             |> Task.async()
             |> Task.await()
    end

    test "never calls expensive function" do
      expect(AnotherModule, :expensive_fun, 1, 0)

      assert Module.fun()
    end
  end
end

License

MIT