def test_handle_generic_http(self, app, client):
        """``HTTPException`` should only receive ``HTTPException``
        subclasses. It will receive ``404`` routing exceptions.
        """

        @app.errorhandler(HTTPException)
        def handle_http(e):
            assert isinstance(e, HTTPException)
            return str(e.code)

        assert client.get("/error").data == b"500"
        assert client.get("/abort").data == b"500"
        assert client.get("/not-found").data == b"404"
``HTTPException`` should only receive ``HTTPException``
        subclasses. It will receive ``404`` routing exceptions.
        
tests/test_user_error_handler.py