How to test Fastapi Exception Handler

Question

I created a custom exception handler and wanted to write test cases for it.

This is my Testcase:

def test_is_exception_raised(app_client):
    exception = CustomException(InvalidSQLStatement())
    with pytest.raises(exception):
        raise exception

    try:
        raise exception
    except Exception as e:
        assert e.message
        assert e.status_code

This is the error I get:

My Code looks like this: main.py

@app.exception_handler(CustomException)
async def custom_exception_handler(request: Request, exc: CustomException):
    log.error(f"{exc}")
    return JSONResponse(
        status_code=exc.status_code_number,
        content=jsonable_encoder({exc.status_code_number: exc.message}),
    )

exceptions.py

class CustomException(Exception):
    """
    All Custom Exceptions are defined in xyz\exceptions.py
    """

    def __init__(self, exception):
        if not check_if_exception_exists(exception):
            raise KeyError(f"Custom Exception: {exception.__class__.__name__} does not exist.")
        self.message = exception.message
        self.status_code_number = exception.status_code_number

Answer 1

You need to use raises in the class, like this:

with pytest.raises(CustomException):

Also, you declare status_code_number (in exceptions.py), but use status_code in test case.