* extension will be omitted.
     */
    fun addSubjectAlternativeName(altName: String) =
      apply {
        altNames += altName
      }

    /**
     * Set this certificate's common name (CN). Historically this held the hostname of TLS
     * certificate, but that practice was deprecated by [RFC 2818][rfc_2818] and replaced with
     * [addSubjectAlternativeName]. If unset a random string will be used.
     *

        val heldCertificate =
          HeldCertificate
            .Builder()
            .commonName("localhost")
            .addSubjectAlternativeName("localhost")
            .rsa2048()
            .build()
        return@lazy HandshakeCertificates
          .Builder()
          .heldCertificate(heldCertificate)

      HeldCertificate
        .Builder()
        .certificateAuthority(0)
        .build()
    val serverCertificate =
      HeldCertificate
        .Builder()
        .signedBy(serverCa)
        .addSubjectAlternativeName(server.hostName)
        .build()
    val serverHandshakeCertificates =
      HandshakeCertificates
        .Builder()
        .addTrustedCertificate(clientCa.certificate)

      HeldCertificate
        .Builder()
        .certificateAuthority(0)
        .build()
    val serverCertificate =
      HeldCertificate
        .Builder()
        .signedBy(serverCa)
        .addSubjectAlternativeName(server.hostName)
        .build()
    val serverHandshakeCertificates =
      HandshakeCertificates
        .Builder()
        .addTrustedCertificate(clientCa.certificate)

    server.enqueue(MockResponse())
    val serverCertificate =
      HeldCertificate
        .Builder()
        .commonName("localhost") // Unusued for hostname verification.
        .addSubjectAlternativeName("wronghostname")
        .build()
    val serverCertificates =
      HandshakeCertificates
        .Builder()
        .heldCertificate(serverCertificate)
        .build()

    var builder: HeldCertificate.Builder = HeldCertificate.Builder()
    builder = builder.validityInterval(0L, 0L)
    builder = builder.duration(0L, TimeUnit.SECONDS)
    builder = builder.addSubjectAlternativeName("")
    builder = builder.commonName("")
    builder = builder.organizationalUnit("")
    builder = builder.serialNumber(BigInteger.ZERO)
    builder = builder.serialNumber(0L)