def test_previous_instruction_in_scope_failures(self):
"""Test the failure paths of the peek and pop methods for retrieving the most recent
instruction in a scope."""
test = QuantumCircuit(1, 1)
with self.assertRaisesRegex(CircuitError, r"This circuit contains no instructions\."):
test._peek_previous_instruction_in_scope()
with self.assertRaisesRegex(CircuitError, r"This circuit contains no instructions\."):
test._pop_previous_instruction_in_scope()
with test.for_loop(range(2)):
with self.assertRaisesRegex(CircuitError, r"This scope contains no instructions\."):
test._peek_previous_instruction_in_scope()
with self.assertRaisesRegex(CircuitError, r"This scope contains no instructions\."):
test._pop_previous_instruction_in_scope()
def test_pop_previous_instruction_removes_parameters(self):
"""Test that the private "pop instruction" method removes parameters from the parameter
table if that instruction is the only instance."""
x, y = Parameter("x"), Parameter("y")
test = QuantumCircuit(1, 1)
test.rx(y, 0)
last_instructions = test.u(x, y, 0, 0)
self.assertEqual({x, y}, set(test.parameters))
instruction = test._pop_previous_instruction_in_scope()
self.assertEqual(list(last_instructions), [instruction])
self.assertEqual({y}, set(test.parameters))
