val recorded = server.takeRequest()
    assertThat(recorded.headers["Accept"]).isEqualTo("text/plain")
    assertThat(recorded.headers["Accept-Encoding"]).isNull() // No built-in gzip.
    assertThat(recorded.headers["Connection"]).isEqualTo("Upgrade, HTTP2-Settings")
    if (PlatformVersion.majorVersion < 19) {
      assertThat(recorded.headers["Content-Length"]).isEqualTo("0")
    }