events.add(Failure(t, response))
    }
  }

  private fun nextEvent(): Any =
    events.poll(10, TimeUnit.SECONDS)
      ?: throw AssertionError("Timed out waiting for event.")

  fun assertTextMessage(payload: String?) {
    assertThat(nextEvent()).isEqualTo(Message(string = payload))
  }

  fun assertBinaryMessage(payload: ByteString?) {
    assertThat(nextEvent()).isEqualTo(Message(payload))
  }