}

  @Test
  fun worksIfTrailersSet() {
    val response =
      newResponse("".toResponseBody()) {
        trailers(
          object : TrailersSource {
            override fun get() = Headers.headersOf("a", "b")
          },
        )
      }

    assertThat(response.trailers()["a"]).isEqualTo("b")
  }

  @Test fun peekAfterReadingResponse() {
    val response = newResponse(responseBody("abc"))

  fun writeRequest(
    headers: Headers,
    requestLine: String,
  ) {
    check(state == STATE_IDLE) { "state: $state" }
    socket.sink.writeUtf8(requestLine).writeUtf8("\r\n")
    for (i in 0 until headers.size) {
      socket.sink
        .writeUtf8(headers.name(i))
        .writeUtf8(": ")
        .writeUtf8(headers.value(i))
        .writeUtf8("\r\n")
    }

  public val settings: Settings

  public constructor(
    code: Int = 200,
    headers: Headers = headersOf(),
    body: String = "",
  ) : this(
    Builder()
      .code(code)
      .headers(headers)
      .body(body),
  )

  private constructor(builder: Builder) {
    this.status = builder.status
    this.headers = builder.headers
    this.trailers = builder.trailers
    this.body = builder.body

      value: String,
    ) = apply {
      headers.add(name, value)
    }

    /** Removes all headers named [name] on this builder. */
    open fun removeHeader(name: String) =
      apply {
        headers.removeAll(name)
      }

    /** Removes all headers on this builder and adds [headers]. */
    open fun headers(headers: Headers) =
      apply {
        this.headers = headers.newBuilder()
      }

 * **TlsVersion**: javaName

#### Renamed Functions

* **Headers.of()**: for symmetry with `listOf()`, `setOf()`, etc., we’ve replaced
  `Headers.of(String...)` with `headersOf(vararg String)`.

#### Extension Functions

We’ve migrated from static functions to extension functions where we think they fit.

| Java                                | Kotlin                          |

    val authority = request.headers["Host"] // Has host and port.
    val fancyRequest =
      Request
        .Builder()
        .url("$scheme://$authority/")
        .headers(request.headers)
        .build()
    val fancyResponse =
      Response
        .Builder()
        .code(webSocketResponse.code)
        .message(webSocketResponse.message)
        .headers(webSocketResponse.headers)

    assertEquals(setOf(OkHttpTest::class.java.name), testHandler.calls.keys)
  }

  fun testCachedRequest() {
    enableTls()

    server.enqueue(MockResponse(body = "abc", headers = Headers.headersOf("cache-control", "public, max-age=3")))
    server.enqueue(MockResponse(body = "abc"))

    val ctxt = InstrumentationRegistry.getInstrumentation().targetContext.applicationContext

  }

  @Test
  fun emptyResponseHeaderNameFromCacheIsLenient() {
    val headers =
      Headers
        .Builder()
        .add("Cache-Control: max-age=120")
    addHeaderLenient(headers, ": A")
    server.enqueue(
      MockResponse
        .Builder()
        .headers(headers.build())
        .body("body")
        .build(),
    )
    val response = get(server.url("/"))

	AmzMetaUnencryptedContentLength = "X-Amz-Meta-X-Amz-Unencrypted-Content-Length"
	AmzMetaUnencryptedContentMD5    = "X-Amz-Meta-X-Amz-Unencrypted-Content-Md5"

	// AWS server-side encryption headers for SSE-S3, SSE-KMS and SSE-C.
	AmzServerSideEncryption                      = "X-Amz-Server-Side-Encryption"
	AmzServerSideEncryptionKmsID                 = AmzServerSideEncryption + "-Aws-Kms-Key-Id"

And as the `Response` can be used frequently to set headers and cookies, **FastAPI** also provides it at `fastapi.Response`.

///

## Custom Headers { #custom-headers }

Keep in mind that custom proprietary headers can be added <a href="https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers" class="external-link" target="_blank">using the `X-` prefix</a>.