Add few more return-type annotations to tests

Follow up to quantumlib#7327, related to quantumlib#4393.

Author: pavoljuhas

cirq-core/cirq/contrib/qasm_import/_parser_test.py

@@ -979,7 +979,7 @@ def test_two_qubit_gates(qasm_gate: str, cirq_gate: cirq.testing.TwoQubitGate) -
 )
 def test_two_qubit_param_gates(
     qasm_gate: str, cirq_gate: cirq.testing.TwoQubitGate, num_params: int
-):
+) -> None:
     params = '(0.1, 0.2, 0.3)' if num_params == 3 else '(0.1)'
     qasm = f"""
     OPENQASM 2.0;

cirq-core/cirq/testing/random_circuit_test.py

@@ -77,7 +77,7 @@ def test_random_circuit(
     op_density: float,
     gate_domain: Optional[Dict[cirq.Gate, int]],
     pass_qubits: bool,
-):
+) -> None:
     qubit_set = cirq.LineQubit.range(n_qubits)
     qubit_arg = qubit_set if pass_qubits else n_qubits
     circuit = cirq.testing.random_circuit(qubit_arg, n_moments, op_density, gate_domain)

cirq-core/cirq/transformers/analytical_decompositions/two_qubit_to_cz_test.py

@@ -149,7 +149,7 @@ def assert_ops_implement_unitary(q0, q1, operations, intended_effect, atol=0.01)
 )
 def test_two_to_ops_equivalent_and_bounded_for_known_and_random(
     max_partial_cz_depth, max_full_cz_depth, effect
-):
+) -> None:
     q0 = cirq.NamedQubit('q0')
     q1 = cirq.NamedQubit('q1')
 

cirq-core/cirq/transformers/analytical_decompositions/two_qubit_to_fsim_test.py

@@ -98,7 +98,7 @@ def test_decompose_xx_yy_into_two_fsims_ignoring_single_qubit_ops_fail() -> None
 @pytest.mark.parametrize('obj,fsim_gate', itertools.product(UNITARY_OBJS, FEASIBLE_FSIM_GATES))
 def test_decompose_two_qubit_interaction_into_four_fsim_gates_equivalence(
     obj: Any, fsim_gate: cirq.FSimGate
-):
+) -> None:
     qubits = obj.qubits if isinstance(obj, cirq.Operation) else cirq.LineQubit.range(2)
     circuit = cirq.decompose_two_qubit_interaction_into_four_fsim_gates(obj, fsim_gate=fsim_gate)
     desired_unitary = obj if isinstance(obj, np.ndarray) else cirq.unitary(obj)

cirq-core/cirq/transformers/routing/line_initial_mapper_test.py

@@ -159,7 +159,7 @@ def test_small_circuit_on_ring_device() -> None:
 )
 def test_random_circuits_grid_device(
     qubits: int, n_moments: int, op_density: float, random_state: int
-):
+) -> None:
     c_orig = cirq.testing.random_circuit(
         qubits=qubits, n_moments=n_moments, op_density=op_density, random_state=random_state
     )
@@ -176,7 +176,7 @@ def test_random_circuits_grid_device(
 )
 def test_large_random_circuits_grid_device(
     qubits: int, n_moments: int, op_density: float, random_state: int
-):
+) -> None:
     c_orig = cirq.testing.random_circuit(
         qubits=qubits, n_moments=n_moments, op_density=op_density, random_state=random_state
     )