exception_handlers not triggered during unit tests

Hi, I’m using exception_handlers to handle 500 and 503 HTTP codes. However when unit testing, they are ignored. If I start the server and test the route, the handler works properly.

# main.py
@app.exception_handler(Exception)
def handle_500_error(request: Request, exception: Exception) -> JSONResponse:
    return JSONResponse(
        status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
        content=json.dumps({"detail":'Internal Server Error, contact support'}),
    )

@app.exception_handler(OperationalError)
def handle_503_error(request: Request, exception: Exception) -> JSONResponse:
    return JSONResponse(
        status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
        content=json.dumps({"detail":'Service Unavailable, contact support'}),
# function

@router.get("/{partner_id}")
def get_partner_by_id(partner_id: str, db: Session = Depends(get_db)):
    """
    Retrieve a partner from the database by given id
    :param [partner_id]: id to be searched
    :returns: partner data
    """
    db_partner = search_partner_by_id(db=db, partner_id=partner_id)
    if not db_partner:
        raise HTTPException(
            status_code=status.HTTP_404_NOT_FOUND, detail="Partner not found"
        )
    return Partner.from_orm(db_partner).dict(by_alias=True)

# test


def test_get_partner_by_id_503(client: TestClient, valid_body: dict) -> None:
    with patch(
        "partner_api.routers.partners.search_partner_by_id", side_effect=OperationalError
    ):
        query = f"/partners/{valid_body['id']}"
        response = client.get(query)
        assert (
            response.status_code == status.HTTP_503_SERVICE_UNAVAILABLE
        ), response.json()

Environment

Python 3.8.6 fastapi==0.63.0

[gusmith]

@lays147 This may be indeed the same issue as #2799 In my case, the solution was to update one of the argument from the TestClient: raise_server_exceptions which is by default set to True. You are not showing how you build the test client, but if you create it this way:

client = TestClient(app, raise_server_exceptions=False)

the server should not raise the exceptions when they occur, but instead return the http error you are expecting. In the docs from starlette

By default the TestClient will raise any exceptions that occur in the application. Occasionally you might want to test the content of 500 error responses, rather than allowing client to raise the server exception. In this case you should use client = TestClient(app, raise_server_exceptions=False).

[lays147]

@Kludex thanks for the tip. Ok, but that does not explain why both handlers work when I have the server running and testing via curl or why the handler for OperationalError does not work during the unit test. Also, the code sample is reproducible, as you can see on the test I’m mocking the database function to raise the exception, one just need to setup the fast API app.