* more information, see the comments in that class.
       *
       * We already know that that's how it behaves, and subclasses of Converter can't change that
       * behavior. So there's no sense in making all subclass authors exclude the method from any
       * NullPointerTester tests that they have.
       */
      ignoredMembers.add(Converter.class.getMethod("apply", Object.class));

    //                                                                    Helper Classes
    //                                                                    ================

    /**
     * Testable subclass that bypasses ComponentUtil dependencies.
     * This allows testing the filter logic without requiring the DI container.
     */
    private static class TestableLoadControlFilter extends LoadControlFilter {

 *
 * <p>Subclasses are guaranteed that the life cycle methods ({@link #runOneIteration}, {@link
 * #startUp} and {@link #shutDown}) will never run concurrently. Notably, if any execution of {@link
 * #runOneIteration} takes longer than its schedule defines, then subsequent executions may start
 * late. Also, all life cycle methods are executed with a lock held, so subclasses can safely modify

        final TestableGroovyEngine testEngine = new TestableGroovyEngine();
        assertEquals("groovy", testEngine.testGetName());
    }

    /**
     * Testable GroovyEngine subclass for testing protected methods
     */
    static class TestableGroovyEngine extends GroovyEngine {
        boolean logScriptExecutionCalled = false;
        String lastLoggedScript = null;

        final List<Map<String, Object>> result = chatClient.testSearchWithQuery("nonexistent");
        assertTrue(result.isEmpty());
    }

    // ========== Testable subclass ==========

    static class TestableChatClient extends ChatClient {

        private boolean searchDocumentsCalled = false;
        private final List<String> searchedQueries = new ArrayList<>();

這個簡單情境會由 FastAPI 自動處理，因為回傳型別註解是 `Response` 類別（或其子類別）。

而工具也會滿意，因為 `RedirectResponse` 與 `JSONResponse` 都是 `Response` 的子類別，所以型別註解是正確的。

### 註解為某個 Response 的子類別 { #annotate-a-response-subclass }

你也可以在型別註解中使用 `Response` 的子類別：

{* ../../docs_src/response_model/tutorial003_03_py310.py hl[8:9] *}

這同樣可行，因為 `RedirectResponse` 是 `Response` 的子類別，而 FastAPI 會自動處理這種簡單情況。

                + "\"instanceId\":\"node1@host1\",\"status\":\"running\"," + "\"expiredTime\":" + (now + 3600000L) + "}}";
        final CurlResponse mockResponse = createMockResponse(200, opJson);

        // Use a subclass to mock both CurlHelper access and getActiveInstances
        final CoordinatorHelper helper = new CoordinatorHelper() {
            @Override
            public List<InstanceInfo> getActiveInstances() {

  might have multiple nodes.
* **`ESRestTestCase`**: An integration tests that interacts with an external
  cluster via the REST API. This is used for Java based REST tests.
* **`ESClientYamlSuiteTestCase` **: A subclass of `ESRestTestCase` used to run
  YAML based REST tests.

=== Good practices

==== What kind of tests should I write?

Unit tests are the preferred way to test some functionality: most of the time

    }

    @Override
    public void forEach(Consumer<? super T> action) {
      iterable.forEach(action);
    }

    @SuppressWarnings("unchecked") // safe upcast, assuming no one has a crazy Spliterator subclass
    @Override
    public Spliterator<T> spliterator() {
      return (Spliterator<T>) iterable.spliterator();
    }

    @Override
    public String toString() {
      return iterable.toString();

Akıttığınız veri türüne uygun `Content-Type` header'ını ayarlayan, `StreamingResponse`'tan türetilmiş özel bir alt sınıf (subclass) oluşturabilirsiniz.

Örneğin, `media_type` özniteliğini kullanarak `Content-Type` header'ını `image/png` olarak ayarlayan bir `PNGStreamingResponse` oluşturabilirsiniz: