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._validate_parameter_shift(dev)
def test_parameter_shift_cv_device(self):
"""Test that the _validate_parameter_shift method
returns the correct gradient transform for cv devices."""
dev = qml.device("default.gaussian", wires=1)
gradient_fn = QNode._validate_parameter_shift(dev)
assert gradient_fn[0] is qml.gradients.param_shift_cv
assert gradient_fn[1] == {"dev": dev}
def test_parameter_shift_qubit_device(self):
"""Test that the _validate_parameter_shift method
returns the correct gradient transform for qubit devices."""
dev = qml.device("default.qubit", wires=1)
gradient_fn = QNode._validate_parameter_shift(dev)
assert gradient_fn[0] is qml.gradients.param_shift
