sink.close()
    assertThat<ByteString>(future1.get())
      .isEqualTo("abcdefghijklmnopqrst".encodeUtf8())
    assertThat<ByteString>(future2.get())
      .isEqualTo("abcdefghijklmnopqrst".encodeUtf8())
    assertThat(relay.isClosed).isTrue()
    assertFile(Relay.PREFIX_CLEAN, 20L, metadata.size, "abcdefghijklmnopqrst", metadata)
  }