Repatch is a library for efficient, ergonomic and concise mocking/patching in tests (or not tests)

1. Patch any function or macro (except NIF and BIF). Elixir or Erlang, private or public, it can be patched!

2. Designed to work with async: true. Has 3 isolation levels for testing multi-processes scenarios.

3. Requires no boilerplate or explicit DI. Though, you are completely free to write in this style with Repatch!

4. Every patch is consistent and applies to direct or indirect calls and any process you choose.

5. Powerful call history tracking.

6. super and real helpers for calling original functions.

7. Works with other testing frameworks and even in environments like iex or remote shell.

8. Get async-friendly application env! with just a single line in test. See Repatch.Application.

def deps do
  [
    {:repatch, "~> 1.0"}
  ]
end

for ExUnit users

1. Add Repatch.setup() into your test_helper.exs file after the ExUnit.start()

2. use Repatch.ExUnit in your test module

3. Call Repatch.patch or Repatch.fake to change implementation of any function and any module.

defmodule ThatsATest do
  use ExUnit.Case, async: true
  use Repatch.ExUnit

  test "that's not a MapSet.new" do
    Repatch.patch(MapSet, :new, fn ->
      %{thats_not: :a_map_set}
    end)

    assert MapSet.new() == %{thats_not: :a_map_set}

    assert Repatch.called?(MapSet, :new, 1)
  end
end

Please check out the docs for all available features.

To ihumanable for Patch library which was an inspiration and a good example for Repatch.