Fix fake backend kwargs

qiskit/test/mock/fake_backend.py

@@ -148,7 +148,7 @@ def run(self, run_input, **kwargs):
                     from qiskit.providers.aer.noise import NoiseModel
 
                     noise_model = NoiseModel.from_backend(self, warnings=False)
-                    job = sim.run(circuits, noise_model=noise_model)
+                    job = sim.run(circuits, noise_model=noise_model, **kwargs)
                 else:
                     job = sim.run(circuits, **kwargs)
         else:

releasenotes/notes/fix-kwargs-mock-f581d5118a1c7589.yaml

@@ -0,0 +1,11 @@
+---
+fixes:
+  - |
+    Fixed an issue with the mock backends located in ``qiskit.test.mock`` where
+    in some situations (mainly fake backends with stored
+    :class:`~qiskit.providers.models.BackendProperties` running a
+    :class:`~qiskit.circuit.QuantumCircuit` with ``qiskit-aer`` installed)
+    passing run time options to the ``run()`` method of a fake backend object
+    would not actually be passed to the simulator underlying the ``run()``
+    method and not have any effect.
+    Fixed `#6741 <https://github.com/Qiskit/qiskit-terra/issues/6741>`__

test/python/mock/test_fake_backends.py

@@ -19,6 +19,7 @@
 from qiskit.qobj import PulseQobj
 from qiskit.test import QiskitTestCase
 from qiskit.test.mock.utils import ConfigurableFakeBackend
+from qiskit.test.mock import FakeAthens
 
 from qiskit.test.mock.fake_backend import HAS_AER
 
@@ -64,3 +65,21 @@ def test_transpile_schedule_and_assemble(self):
         result = job.result()
         self.assertTrue(result.success)
         self.assertEqual(len(result.results), 1)
+
+
+class FakeBackendsTest(QiskitTestCase):
+    """fake backends test."""
+
+    @unittest.skipUnless(HAS_AER, "qiskit-aer is required to run this test")
+    def test_fake_backends_get_kwargs(self):
+        """Fake backends honor kwargs passed."""
+        backend = FakeAthens()
+
+        qc = QuantumCircuit(2)
+        qc.x(range(0, 2))
+        qc.measure_all()
+
+        trans_qc = transpile(qc, backend)
+        raw_counts = backend.run(trans_qc, shots=1000).result().get_counts()
+
+        self.assertEqual(sum(raw_counts.values()), 1000)