} catch (IllegalArgumentException e) {
      // Make sure we expected this.
      assertNull(expectHost);
      return;
    }
    assertNotNull(expectHost);

    // Apply withDefaultPort(), yielding hp2.
    final boolean badDefaultPort = (defaultPort < 0 || defaultPort > 65535);
    HostAndPort hp2 = null;
    try {
      hp2 = hp.withDefaultPort(defaultPort);
      assertFalse(badDefaultPort);