Update backend.run to handle list of size one

.pylintrc

@@ -74,7 +74,8 @@ disable=no-self-use,        # disabled as it is too verbose
     missing-yield-doc,      # in coroutines, these checks can yield false
     missing-yield-type-doc,  # positives (pun intended)
     import-outside-toplevel,
-    docstring-first-line-empty
+    docstring-first-line-empty,
+    R1732
 
 
 [REPORTS]

qiskit_ionq/ionq_backend.py

@@ -31,6 +31,7 @@
 import dateutil.parser
 from qiskit.providers import BackendV1 as Backend
 from qiskit.providers.models import BackendConfiguration
+from qiskit.providers.models.backendstatus import BackendStatus
 from qiskit.providers import Options
 
 from . import exceptions, ionq_client, ionq_job
@@ -175,13 +176,27 @@ def create_client(self):
     def run(self, circuit, **kwargs):
         """Create and run a job on an IonQ Backend.
 
+        .. NOTE::
+
+            IonQ backends do not support multi-experiment jobs.
+            If ``circuit`` is provided as a list with more than one element
+            then this method will raise out with a RuntimeError.
+
         Args:
             circuit (:class:`QuantumCircuit <qiskit.circuit.QuantumCircuit>`):
                 A Qiskit QuantumCircuit object.
 
         Returns:
             IonQJob: A reference to the job that was submitted.
+
+        Raises:
+            RuntimeError: If a multi-experiment circuit was provided.
         """
+        if isinstance(circuit, (list, tuple)):
+            if len(circuit) > 1:
+                raise RuntimeError("Multi-experiment jobs are not supported!")
+            circuit = circuit[0]
+
         for kwarg in kwargs:
             if not hasattr(self.options, kwarg):
                 warnings.warn(
@@ -206,18 +221,24 @@ def retrieve_job(self, job_id):
         return ionq_job.IonQJob(self, job_id, self.client)
 
     def retrieve_jobs(self, job_ids):
-        """get a list of jobs from a specific backend, job id """
+        """get a list of jobs from a specific backend, job id"""
 
         return [ionq_job.IonQJob(self, job_id, self.client) for job_id in job_ids]
 
     # TODO: Implement backend status checks.
     def status(self):
-        """Not yet implemented.
+        """Return a backend status object to the caller.
 
-        Raises:
-            NotImplementedError: This behavior is not currently supported.
+        Returns:
+            BackendStatus: the status of the backend.
         """
-        raise NotImplementedError("Backend status check is not supported.")
+        return BackendStatus(
+            backend_name=self.name(),
+            backend_version="1",
+            operational=True,
+            pending_jobs=0,
+            status_msg="",
+        )
 
     def calibration(self):
         """Fetch the most recent calibration data for this backend.

test/ionq_backend/test_base_backend.py

@@ -31,23 +31,22 @@
 
 import pytest
 from qiskit import QuantumCircuit
+from qiskit.providers.models.backendstatus import BackendStatus
 
 from qiskit_ionq import exceptions, ionq_client, ionq_job
 
 from .. import conftest
 
 
-def test_status_not_implemented(mock_backend):
-    """Test that by default, `status` is not implemented.
+def test_status_dummy_response(mock_backend):
+    """Test that the IonQBackend returns an aribtrary backend status.
 
     Args:
         mock_backend (MockBackend): A fake/mock IonQBackend.
     """
-
-    with pytest.raises(NotImplementedError) as exc_info:
-        mock_backend.status()
-
-    assert str(exc_info.value) == "Backend status check is not supported."
+    status = mock_backend.status()
+    assert isinstance(status, BackendStatus)
+    assert status.operational is True
 
 
 def test_client_property(mock_backend):
@@ -128,7 +127,7 @@ def test_create_client_exceptions(mock_backend, creds, msg):
 
 
 def test_run(mock_backend, requests_mock):
-    """Test that the backend `run` submits a job and returns that job.
+    """Test that the backend `run` submits a circuit and returns its job.
 
     Args:
         mock_backend (MockBackend): A fake/mock IonQBackend.
@@ -145,3 +144,35 @@ def test_run(mock_backend, requests_mock):
 
     assert isinstance(job, ionq_job.IonQJob)
     assert job.job_id() == "fake_job"
+
+
+def test_run_single_element_list(mock_backend, requests_mock):
+    """Test that the backend `run` submits a circuit in a single-element list.
+
+    Args:
+        mock_backend (MockBackend): A fake/mock IonQBackend.
+        requests_mock (:class:`request_mock.Mocker`): A requests mocker.
+    """
+    path = mock_backend.client.make_path("jobs")
+    dummy_response = conftest.dummy_job_response("fake_job")
+
+    # Mock the call to submit:
+    requests_mock.post(path, json=dummy_response, status_code=200)
+
+    # Run a dummy circuit.
+    job = mock_backend.run([QuantumCircuit(1, 1)])
+
+    assert isinstance(job, ionq_job.IonQJob)
+    assert job.job_id() == "fake_job"
+
+
+def test_run_raises_multiexp_job(mock_backend):
+    """Test that the backend `run` raises out if more than one circuit is provided.
+
+    Args:
+        mock_backend (MockBackend): A fake/mock IonQBackend.
+    """
+    # Run a dummy circuit.
+    with pytest.raises(RuntimeError) as excinfo:
+        mock_backend.run([QuantumCircuit(1, 1), QuantumCircuit(1, 1)])
+    assert str(excinfo.value) == "Multi-experiment jobs are not supported!"