When a client disconnects, a `WebSocketDisconnect` exception is raised, you can catch it.

You can import it directly form `fastapi`:

```python
from fastapi import WebSocketDisconnect
```

::: fastapi.WebSocketDisconnect

## WebSockets - additional classes

Additional classes for handling WebSockets.

Provided directly by Starlette, but you can import it from `fastapi`:

```python

# and also repacks libtensorflow-src.jar into a standardized format.

# Helper function to copy a srcjar after moving any source files
# directly under the root to the "maven-style" src/main/java layout
#
# Source files generated by annotation processors appear directly
# under the root of srcjars jars created by bazel, rather than under
# the maven-style src/main/java subdirectory.
#

import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code element()} operations on a queue. Can't be invoked
 * directly; please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
 *
 * @author Jared Levy
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.

import org.junit.Ignore;

/**
 * A generic JUnit test which tests {@code peek()} operations on a queue. Can't be invoked directly;
 * please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
 *
 * @author Jared Levy
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.

import org.junit.Ignore;

/**
 * A generic JUnit test which tests addAll operations on a set. Can't be invoked directly; please
 * see {@link com.google.common.collect.testing.SetTestSuiteBuilder}.
 *
 * @author Kevin Bourrillion
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.

        errorResponse.message(testMessage);
        errorResponse.status(Status.BAD_REQUEST);
        ApiResult result = errorResponse.result();

        assertNotNull(result);
        // Cannot directly access protected fields, just verify the result is not null
    }

    // Test configuration for JSON response
    public void test_configurationSettings() {
        ComponentUtil.setFessConfig(new FessConfig.SimpleImpl() {

/**
 * A generic JUnit test which tests {@code add(int, Object)} operations on a list. Can't be invoked
 * directly; please see {@link com.google.common.collect.testing.ListTestSuiteBuilder}.
 *
 * @author Chris Povirk
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.

    private NdrBuffer mockNdrBuffer;

    @Mock
    private NdrBuffer mockDeferredBuffer;

    @BeforeEach
    void setUp() {
        MockitoAnnotations.openMocks(this);
        // Set the deferred field directly since it's a public field, not a method
        mockNdrBuffer.deferred = mockDeferredBuffer;
        lenient().when(mockNdrBuffer.derive(anyInt())).thenReturn(mockDeferredBuffer);

You can use the `TestClient` class to test FastAPI applications without creating an actual HTTP and socket connection, just communicating directly with the FastAPI code.

Read more about it in the [FastAPI docs for Testing](https://fastapi.tiangolo.com/tutorial/testing/).

You can import it directly from `fastapi.testclient`:

```python
from fastapi.testclient import TestClient
```

/**
 * A generic JUnit test which tests {@code clear()} operations on a collection. Can't be invoked
 * directly; please see {@link com.google.common.collect.testing.CollectionTestSuiteBuilder}.
 *
 * @author George van den Driessche
 */
@GwtCompatible
@Ignore("test runners must not instantiate and run this directly, only via suites we build")
// @Ignore affects the Android test runner, which respects JUnit 4 annotations on JUnit 3 tests.