def test_parameter_shift_tape_unknown_model(self, monkeypatch):
"""test that an unknown model raises an exception"""
def capabilities(cls):
capabilities = cls._capabilities
capabilities.update(model="None")
return capabilities
monkeypatch.setattr(qml.devices.DefaultQubit, "capabilities",
capabilities)
dev = qml.device("default.qubit", wires=1)
with pytest.raises(qml.QuantumFunctionError,
match="does not support the parameter-shift rule"):
QNode._get_parameter_shift_tape(dev)
def test_parameter_shift_tape_qubit_device(self):
"""Test that the get_parameter_shift_method method correctly and
returns the correct tape for qubit devices."""
dev = qml.device("default.qubit", wires=1)
tape_class = QNode._get_parameter_shift_tape(dev)
assert tape_class is QubitParamShiftTape