synchronize_death_on_exit.ex

    @doc """
    Will ensure the processes with the test does not complete until the process with the
    provided pid has exited. This is necessary when writing multiple tests that start the
    same named process. See https://github.com/elixir-lang/elixir/issues/3854 for more info.

    This accepts either `{:ok, pid}` or just `pid` so that you can use it in a pipeline
    after a `start_link` call.
    """
    def synchronize_death_on_exit({:ok, pid}) when is_pid(pid), do: synchronize_death_on_exit(pid)
    def synchronize_death_on_exit(pid) when is_pid(pid) do
      ExUnit.Callbacks.on_exit fn ->
        ref = Process.monitor(pid)
        receive do
          {:DOWN, ^ref, _, _, _} -> :ok
        end
      end

      pid
    end