.certificateAuthority(1)
        .commonName("root")
        .addSubjectAlternativeName("root_ca.com")
        .build()
    serverIntermediateCa =
      HeldCertificate
        .Builder()
        .signedBy(serverRootCa)
        .certificateAuthority(0)
        .serialNumber(2L)
        .commonName("intermediate_ca")
        .addSubjectAlternativeName("intermediate_ca.com")
        .build()
    serverCert =

[builder][held_certificate_builder] to create a self-signed certificate that a test server can use
for HTTPS:

```java
HeldCertificate localhostCertificate = new HeldCertificate.Builder()
    .addSubjectAlternativeName("localhost")
    .build();
```

[`HandshakeCertificates`][handshake_certificates] keeps the certificates for a TLS handshake.

        .commonName("attacker")
        .addSubjectAlternativeName("attacker.com")
        .signedBy(pinnedIntermediate)
        .build()
    val phonyVictim =
      HeldCertificate
        .Builder()
        .serialNumber(6L)
        .signedBy(attackerSwitch)
        .addSubjectAlternativeName("victim.com")
        .commonName("victim")
        .build()

     * 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.
     *

    run {
      // Generate a self-signed cert for the server to serve and the client to trust.
      val heldCertificate =
        HeldCertificate
          .Builder()
          .commonName(hostname)
          .addSubjectAlternativeName(hostname)
          .build()
      HandshakeCertificates
        .Builder()
        .heldCertificate(heldCertificate)
        .addTrustedCertificate(heldCertificate.certificate)
        .build()
    }

        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)