wait_for_pid - Do I even need this as a test helper? I'm not sure...

wait_for.exs

  @wait_time 25
  # Base case: We have a pid
  def wait_for(pid) when is_pid(pid), do: continue_waiting(pid)
  # Failure case: We failed to find a pid for a module.
  def wait_for(nil), do: raise("Attempted to wait on bad module/pid")
  # Edge case: We have a module and need to try finding its pid.
  def wait_for(mod), do: wait_for(Process.whereis(mod))

  defp continue_waiting(pid) do
    wait(pid, Process.info(pid, :message_queue_len))
  end

  defp wait(_pid, {:message_queue_len, 0}), do: Process.sleep(@wait_time)

  defp wait(pid, {:message_queue_len, _n}) do
    Process.sleep(@wait_time)
    continue_waiting(pid)
  end