t.Fatalf("Test %d: %s: Failed to create HTTP request for Head Object: <ERROR> %v", i+1, instanceType, err)
		}
		// Since `apiRouter` satisfies `http.Handler` it has a ServeHTTP to execute the logic of the handler.
		// Call the ServeHTTP to execute the handler,`func (api objectAPIHandlers) GetObjectHandler`  handles the request.
		apiRouter.ServeHTTP(rec, req)

		// Assert the response code with the expected status.

		}
		h.ServeHTTP(w, r)
	})
}

// criticalErrorHandler handles panics and fatal errors by
// `panic(logger.ErrCritical)` as done by `logger.CriticalIf`.
//
// It should be always the first / highest HTTP handler.
func setCriticalErrorHandler(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		defer func() {

			return newMuxStateless(ctx, m, c, *handler)
		})
	} else {
		// Stream:
		var handler *StreamHandler
		if subID == nil {
			if !m.Handler.valid() {
				gridLogIf(ctx, c.queueMsg(m, muxConnectError{Error: "Invalid Handler"}))
				return
			}
			handler = c.handlers.streams[m.Handler]
		} else {
			handler = c.handlers.subStreams[*subID]
		}
		if handler == nil {

	if err != nil {
		t.Fatalf("Test %s: Failed to create HTTP request for RemoveBucketHandler: <ERROR> %v", instanceType, err)
	}
	// Since `apiRouter` satisfies `http.Handler` it has a ServeHTTP to execute the logic of the handler.
	// Call the ServeHTTP to execute the handler.
	apiRouter.ServeHTTP(rec, req)
	switch rec.Code {
	case http.StatusOK, http.StatusCreated, http.StatusAccepted, http.StatusNoContent:

			t.Fatalf("Test %d: Failed to create HTTP request for GetBucketPolicyHandler: <ERROR> %v", i+1, err)
		}
		// Since `apiRouter` satisfies `http.Handler` it has a ServeHTTP to execute the logic of the handler.
		// Call the ServeHTTP to execute the handler, GetBucketPolicyHandler handles the request.
		apiRouter.ServeHTTP(recV4, reqV4)
		// Assert the response code with the expected status.
		if recV4.Code != testCase.expectedRespStatus {

And it also includes a default exception handler for it.

To override it, import the `RequestValidationError` and use it with `@app.exception_handler(RequestValidationError)` to decorate the exception handler.

The exception handler will receive a `Request` and the exception.

```Python hl_lines="2  14-16"
{!../../../docs_src/handling_errors/tutorial004.py!}
```

From this connection individual requests can be made.

Each handler, with optional subroutes can be registered with the manager using 
`Manager.RegisterXHandler(handlerID, handler, subroutes...)`.

A `Handler()` function provides an HTTP handler, which should be hooked up to the appropriate route on the server.

			gridLogIf(ctx, fmt.Errorf("grid handler (%v) panic: %v", msg.Handler, r))
			err := RemoteErr(fmt.Sprintf("handler panic: %v", r))
			handlerErr = &err
		}
		if debugPrint {
			fmt.Println("muxServer: Mux", m.ID, "Returned with", handlerErr)
		}
	}()
	// handlerErr is guarded by 'send' channel.
	handlerErr = handler.Handle(ctx, msg.Payload, handlerIn, send)
	return handlerErr
}

app = FastAPI(
    exception_handlers={
        HTTPException: http_exception_handler,
        RequestValidationError: request_validation_exception_handler,
        Exception: server_error_exception_handler,
    }
)

client = TestClient(app)


@app.get("/http-exception")
def route_with_http_exception():
    raise HTTPException(status_code=400)


@app.get("/request-validation/{param}/")

    )


async def request_validation_exception_handler(
    request: Request, exc: RequestValidationError
) -> JSONResponse:
    return JSONResponse(
        status_code=HTTP_422_UNPROCESSABLE_ENTITY,
        content={"detail": jsonable_encoder(exc.errors())},
    )


async def websocket_request_validation_exception_handler(
    websocket: WebSocket, exc: WebSocketRequestValidationError
) -> None: