"Method com.example.Source.baz(): From non-null returning to null-unmarked returning breaking change.",
            )
            assertHasNoWarning()
            assertHasNoInformation()
        }
    }

    @Test
    fun `from null-unmarked returning to non-null returning is not breaking`() {

In this example, the function `generate_html_response()` already generates and returns a `Response` instead of returning the HTML in a `str`.

By returning the result of calling `generate_html_response()`, you are already returning a `Response` that will override the default **FastAPI** behavior.

                errors << "From non-null returning to null returning breaking change"
            } else if (oldNullability == Nullability.NON_NULL && newNullability == Nullability.UNMARKED) {
                errors << "From non-null returning to null-unmarked returning breaking change"
            } else if (oldNullability == Nullability.UNMARKED && newNullability == Nullability.NULLABLE) {

              }
            },
            directExecutor()));
    thingToCancel[0] = serializer.submit(Callables.returning(null), directExecutor());
    results.add(thingToCancel[0]);
    // Enqueue more than enough tasks to force reentrancy.
    for (int i = 0; i < 5; i++) {
      results.add(serializer.submit(Callables.returning(null), directExecutor()));
    }

    manualExecutorTask[0].run();

FastAPI will use this return type to:

* **Validate** the returned data.
    * If the data is invalid (e.g. you are missing a field), it means that *your* app code is broken, not returning what it should, and it will return a server error instead of returning incorrect data. This way you and your clients can be certain that they will receive the data and the data shape expected.
* Add a **JSON Schema** for the response, in the OpenAPI *path operation*.

You can add middleware to **FastAPI** applications.

A "middleware" is a function that works with every **request** before it is processed by any specific *path operation*. And also with every **response** before returning it.

* It takes each **request** that comes to your application.
* It can then do something to that **request** or run any needed code.

        mockNotifications.add(fileNotifyInfo1);
        mockNotifications.add(fileNotifyInfo2);
        mockNotifications.add(fileNotifyInfo3);
    }

    /**
     * Test watch() method returning notifications
     */
    @Test
    void testWatch() throws CIFSException {
        // Setup mock behavior
        when(watchHandle.watch()).thenReturn(mockNotifications);

        // Execute

You can also declare the `Response` parameter in dependencies, and set cookies (and headers) in them.

## Return a `Response` directly { #return-a-response-directly }

You can also create cookies when returning a `Response` directly in your code.

To do that, you can create a response as described in [Return a Response Directly](response-directly.md){.internal-link target=_blank}.

Then set Cookies in it, and then return it:

    class DecodingTests {

        @Test
        @DisplayName("Should decode value correctly")
        void testDecode() throws NdrException {
            // Given: NdrShort and mock returning specific value
            int decodedValue = 200;
            NdrShort ndrShort = new NdrShort(0);
            when(mockBuffer.dec_ndr_short()).thenReturn(decodedValue);

            // When: Decoding the value

        } catch (final UnsupportedEncodingException uee) {
            return 0;
        }
        bufferIndex += len + 1;
        // win98 observed not returning nativeFileSystem
        /* Problems here with iSeries returning ASCII even though useUnicode = true
         * Fortunately we don't really need nativeFileSystem for anything.
        if( byteCount > bufferIndex - start ) {