.build();
```

[`HandshakeCertificates`][handshake_certificates] keeps the certificates for a TLS handshake.
Use its [builder][handshake_certificates_builder] to define which certificates the HTTPS server
returns to its clients. The returned instance can create an `SSLSocketFactory` that implements this
policy:

```java
HandshakeCertificates serverCertificates = new HandshakeCertificates.Builder()

        .build()
    val handshakeCertificates =
      HandshakeCertificates
        .Builder()
        .heldCertificate(heldCertificate)
        .addTrustedCertificate(heldCertificate.certificate)
        .build()

    // Use that certificate on the server and trust it on the client.
    server.useHttps(handshakeCertificates.sslSocketFactory())
    client =
      client

  }

  @Test
  fun handshakeCertificates() {
    val handshakeCertificates = HandshakeCertificates.Builder().build()
    val keyManager: X509KeyManager = handshakeCertificates.keyManager
    val trustManager: X509TrustManager = handshakeCertificates.trustManager
    val sslSocketFactory: SSLSocketFactory = handshakeCertificates.sslSocketFactory()

        .body("ABC")
        .build(),
    )
    client =
      client
        .newBuilder()
        .sslSocketFactory(
          handshakeCertificates.sslSocketFactory(),
          handshakeCertificates.trustManager,
        ).hostnameVerifier(NULL_HOSTNAME_VERIFIER)
        .build()
    val request = Request.Builder().url(server.url("/")).build()
    val response1 = client.newCall(request).execute()

    }
  }

  private fun enableTls() {
    client =
      client
        .newBuilder()
        .sslSocketFactory(
          handshakeCertificates.sslSocketFactory(),
          handshakeCertificates.trustManager,
        ).build()
    server.useHttps(handshakeCertificates.sslSocketFactory())
  }