}
        }, "Multiple close operations should not cause issues");

        // Verify iterator still works after multiple closes
        assertFalse(emptyIterator.hasNext(), "Iterator should still work after multiple closes");
        assertNull(emptyIterator.next(), "Iterator should still return null after multiple closes");
    }

    @Test

        request.addHeader("Host", "example.com");
        key = virtualHostHelper.getVirtualHostKey();
        assertEquals("", key); // Still empty due to caching

        // Test caching by calling again - should return cached value
        key = virtualHostHelper.getVirtualHostKey();
        assertEquals("", key); // Still cached value
    }

    public void test_getVirtualHostKey_withCaching() {

{* ../../docs_src/query_params_str_validations/tutorial002_an_py310.py hl[9] *}

Notice that the default value is still `None`, so the parameter is still optional.

But now, having `Query(max_length=50)` inside of `Annotated`, we are telling FastAPI that we want it to have **additional validation** for this value, we want it to have maximum 50 characters. 😎

/// tip

But it is still recommended to use the ideas above, using multiple classes, instead of these parameters.

This is because the JSON Schema generated in your app's OpenAPI (and the docs) will still be the one for the complete model, even if you use `response_model_include` or `response_model_exclude` to omit some attributes.

            assertTrue(successfulThreads.get() > 0, "At least some threads should complete successfully");

            // 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

            // Refresh should not break anything
            orig.refresh();
            copy.refresh();

            // Both should still return null
            assertNull(orig.getSubject(), "Original should still return null after refresh");
            assertNull(copy.getSubject(), "Clone should still return null after refresh");
        }
    }

    @Test
    @DisplayName("renew: invokes getSubject and returns self")

        auth.resetAuthenticationTimestamp();
        long afterReset = System.currentTimeMillis();

        // Should still not be expired
        assertFalse(auth.isExpired());

        // Wait for original TTL to pass
        Thread.sleep(600);

        // Should still not be expired because we reset
        assertFalse(auth.isExpired());

        // Wait for the full TTL since reset

  // the call, but they may be accessed by other threads for duplex requests.

  /** True if this call still has a request body open. */
  private var requestBodyOpen = false

  /** True if this call still has a response body open. */
  private var responseBodyOpen = false

  /** True if there are more exchanges expected for this call. */

It had the best performance benchmarks at the time (only surpassed by Starlette).

At first, it didn't have an automatic API documentation web UI, but I knew I could add Swagger UI to it.

It had a dependency injection system. It required pre-registration of components, as other tools discussed above. But still, it was a great feature.

Still, in both situations, chances are that **FastAPI** will [still be faster](index.md#performance){.internal-link target=_blank} than (or at least comparable to) your previous framework.

### Dependencies { #dependencies }