@Override
        public void setReadTimeout(int timeout) {
            this.recordedReadTimeout = timeout;
            super.setReadTimeout(timeout);
        }
    }

    /**
     * CurlRequest subclass that overrides only open(URL) to inject a mock connection.
     * This ensures the real connect() code path is exercised (timeout, headers, onConnect, etc.).
     */
    class OpenOverrideCurlRequest extends CurlRequest {

        } catch (Throwable e) {
          // Any Exception is either a RuntimeException or sneaky checked exception.
          //
          // If an exception is thrown by the subclass then we need to make sure that the service
          // notices and transitions to the FAILED state. We do it by calling notifyFailed directly

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。

        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<>();

     * to be passed to the readXxxWireFormat methods. This is
     * actually purer. However, in the case of smb we know the
     * wordCount and byteCount. And since every subclass of
     * ServerMessageBlock would have to perform the same read
     * operation on the input stream, we might as will pull that
     * common functionality into the superclass and read wordCount

                + "\"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() {

    }

    @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();

  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

        assertEquals("Q2", request.getMessages().get(0).getContent());
        assertEquals("Q3", request.getMessages().get(1).getContent());
    }

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

    @FunctionalInterface
    interface StreamChatCapture {
        void capture(LlmChatRequest request, LlmStreamCallback callback);
    }

このシンプルなケースは、戻り値の型アノテーションが `Response` のクラス（またはサブクラス）であるため、FastAPIが自動的に処理します。

また `RedirectResponse` と `JSONResponse` の両方は `Response` のサブクラスなので、ツールも型アノテーションが正しいとして問題にしません。

### `Response`のサブクラスをアノテーションする { #annotate-a-response-subclass }

型アノテーションで `Response` のサブクラスを使うこともできます:

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

これは `RedirectResponse` が `Response` のサブクラスであり、FastAPIがこのシンプルなケースを自動処理するため、同様に動作します。