.allEnabledCipherSuites()
        .build()
    val allTlsVersions =
      ConnectionSpec.Builder(ConnectionSpec.MODERN_TLS)
        .allEnabledTlsVersions()
        .build()
    val set: MutableSet<Any> = CopyOnWriteArraySet()
    assertThat(set.add(ConnectionSpec.MODERN_TLS)).isTrue()
    assertThat(set.add(ConnectionSpec.COMPATIBLE_TLS)).isTrue()
    assertThat(set.add(ConnectionSpec.CLEARTEXT)).isTrue()

    /**
     * Returns the names of the request headers that need to be checked for equality when caching.
     */
    private fun Headers.varyFields(): Set<String> {
      var result: MutableSet<String>? = null
      for (i in 0 until size) {
        if (!"Vary".equals(name(i), ignoreCase = true)) {
          continue
        }

        val value = value(i)
        if (result == null) {