* certificates. Applications that connect to a known set of servers may be able to mitigate
     * this problem with [certificate pinning][CertificatePinner].
     */
    fun addPlatformTrustedCertificates() =
      apply {
        val platformTrustManager = Platform.get().platformTrustManager()
        Collections.addAll(trustedCertificates, *platformTrustManager.acceptedIssuers)
      }

    /**

    builder = builder.heldCertificate(heldCertificate, heldCertificate.certificate)
    builder = builder.addTrustedCertificate(heldCertificate.certificate)
    builder = builder.addPlatformTrustedCertificates()
    val handshakeCertificates: HandshakeCertificates = builder.build()
  }

  @Test
  fun heldCertificate() {
    val heldCertificate: HeldCertificate = HeldCertificate.Builder().build()

    [our DevServer sample][dev_server]:

    ```kotlin
    val clientCertificates = HandshakeCertificates.Builder()
        .addPlatformTrustedCertificates()
        .addInsecureHost("localhost")
        .build()

    val client = OkHttpClient.Builder()
        .sslSocketFactory(clientCertificates.sslSocketFactory(), clientCertificates.trustManager)