test: assert award task scheduled via transaction.on_commit

Address Copilot review: explicitly assert on_commit is invoked so the
race-condition fix is covered. Without it, tests would still pass if
.delay were called directly. Assert on_commit fires in the enabled
case and not in the records-disabled case.

Author: Waleed-Mujahid

openedx/core/djangoapps/programs/tests/test_signals.py

@@ -153,6 +153,7 @@ def test_credentials_enabled(self, mock_on_commit, mock_is_learner_issuance_enab
         handle_course_cert_changed(**self.signal_kwargs)
 
         assert mock_is_learner_issuance_enabled.call_count == 1
+        assert mock_on_commit.call_count == 1
         assert mock_task.call_count == 1
         assert mock_task.call_args[0] == (TEST_USERNAME, str(TEST_COURSE_KEY))
 
@@ -162,15 +163,18 @@ def test_records_enabled(self, mock_on_commit, mock_is_learner_issuance_enabled,
 
         site_config = SiteConfigurationFactory.create(site_values={"course_org_filter": ["edX"]})
 
-        # Correctly sent
+        # Correctly sent (scheduled via transaction.on_commit)
         handle_course_cert_changed(**self.signal_kwargs)
+        assert mock_on_commit.called
         assert mock_task.called
+        mock_on_commit.reset_mock()
         mock_task.reset_mock()
 
         # Correctly not sent
         site_config.site_values["ENABLE_LEARNER_RECORDS"] = False
         site_config.save()
         handle_course_cert_changed(**self.signal_kwargs)
+        assert not mock_on_commit.called
         assert not mock_task.called