This module offers telemetry style event emission for testing purposes.

If you'd like to emit a message to the event stream, you can call emit/1 from your implementation code. This is macro, and will not result in any AST injection when not being compiled in the test env.

defmodule ImplMod do
  use EventEmitter, :emitter

  def implementation do
    # some logic

    emit %{name: :implementation, module: __MODULE__, metadata: %{unique_identifier: some_variable}}
  end
end

If you'd like to await on a message emitted by implementation code, you can call await/3 from your test code after registering a handler for your test process

defmodule TestMod do
  use EventEmitter, :receiver

  test "some test" do
    EventEmitter.add_handler(self())

    # some tricky asynchronous code

    await :implementation, __MODULE__, %{unique_identifier: some_variable}
  end
end

You can use EventEmitter by starting it in your test helper.

# test_helper.exs

EventEmitter.start_link([])

ExUnit.start()