// Test release (still in use because of initial transport acquire)
        session.release();
        assertTrue(session.isInUse(), "Session should still be in use after one release");

        // Test final release
        session.release();
        assertFalse(session.isInUse(), "Session should not be in use after all releases");

**FastAPI** provides it as a convenience for you, the developer. But it comes directly from Starlette.

///

### Before and after the `response` { #before-and-after-the-response }

You can add code to be run with the `request`,  before any *path operation* receives it.

And also after the `response` is generated, before returning it.

            // The rate limiter should still be functional after concurrent access
            assertTrue(concurrentLimiter.checkAttempt("finaluser", "192.168.3.1"),
                    "Rate limiter should still be functional after concurrent operations");

            // Verify that the rate limiter tracked some activity

The same way, you can define logic (code) that should be executed when the application is **shutting down**. In this case, this code will be executed **once**, **after** having handled possibly **many requests**.

Because this code is executed before the application **starts** taking requests, and right after it **finishes** handling requests, it covers the whole application **lifespan** (the word "lifespan" will be important in a second 😉).

                } catch (CIFSException e) {
                    // Expected
                }
            }

            // Circuit should be OPEN after 3 failures
            assertEquals(State.OPEN, customCb.getState(), "Circuit should be OPEN after regular failures");
            assertEquals(3, customCb.getFailureCount(), "Should have 3 failures");

            // Reset for custom predicate test

        // Wipe the password
        authenticator.secureWipePassword();

        // Verify password is cleared after wipe
        char[] passwordAfter = (char[]) passwordField.get(authenticator);
        assertNull(passwordAfter, "Password should be null after wipe");
    }

    @Test
    @DisplayName("Test session ID generation")
    void testSessionIdGeneration() throws Exception {

        assertTrue(checkTarget.exists(), "Target file should exist after rename");

        // Verify content is preserved
        try (InputStream in = checkTarget.getInputStream()) {
            String readContent = new String(in.readAllBytes(), "UTF-8");
            assertEquals(content, readContent, "Content should be preserved after rename");
        }

        // Best effort to verify source is gone

# Background Tasks { #background-tasks }

You can define background tasks to be run *after* returning a response.

This is useful for operations that need to happen after a request, but that the client doesn't really have to be waiting for the operation to complete before receiving the response.

This includes, for example:

* Email notifications sent after performing an action:

FastAPI supports dependencies that do some <abbr title='sometimes also called "exit code", "cleanup code", "teardown code", "closing code", "context manager exit code", etc.'>extra steps after finishing</abbr>.

To do this, use `yield` instead of `return`, and write the extra steps (code) after.

/// tip

Make sure to use `yield` one single time per dependency.

///

/// note | Technical Details

Any function that is valid to use with:

        assertEquals(auth1, auth2);
        assertEquals(auth1.hashCode(), auth2.hashCode());

        // Test inequality with different password
        assertNotEquals(auth1, auth3);

        // Test after password wipe
        auth1.secureWipePassword();
        assertNotEquals(auth1, auth2);
    }

    /**
     * Test concurrent password access and wiping
     */
    @Test