@Test fun clientSentFramesMustBeMasked() {
    data.write("8100".decodeHex())
    assertFailsWith<ProtocolException> {
      serverReader.processNextFrame()
    }.also { expected ->
      assertThat(expected.message)
        .isEqualTo("Client-sent frames must be masked.")
    }
  }

  @Test fun serverSentFramesMustNotBeMasked() {
    data.write("8180".decodeHex())
    assertFailsWith<ProtocolException> {

    // IPv6 colons don't interfere with port numbers or passwords.
    assertThat(parse("http://[::1]:8080/").port).isEqualTo(8080)
    assertThat(parse("http://user:password@[::1]/").password).isEqualTo("password")
    assertThat(parse("http://user:password@[::1]:8080/").host).isEqualTo("::1")

    // Permit the contents of IPv6 addresses to be percent-encoded...

import org.junit.jupiter.api.Assumptions.assumeTrue

object TestUtil {
  @JvmField
  val UNREACHABLE_ADDRESS_IPV4 = InetSocketAddress("198.51.100.1", 8080)
  val UNREACHABLE_ADDRESS_IPV6 = InetSocketAddress("::ffff:198.51.100.1", 8080)

  /** See `org.graalvm.nativeimage.ImageInfo`. */
  @JvmStatic val isGraalVmImage = System.getProperty("org.graalvm.nativeimage.imagecode") != null

  @JvmStatic

017E          ; valid                                  # 1.1  LATIN SMALL LETTER Z WITH CARON
017F          ; mapped                 ; 0073          # 1.1  LATIN SMALL LETTER LONG S
0180          ; valid                                  # 1.1  LATIN SMALL LETTER B WITH STROKE
0181          ; mapped                 ; 0253          # 1.1  LATIN CAPITAL LETTER B WITH HOOK