Added management commands to tests

* added --run-once option to the management commands for testing

django_q/tests/test_commands.py

@@ -0,0 +1,11 @@
+import pytest
+from django.core.management import call_command
+
+
+@pytest.mark.django_db
+def test_qcluster():
+    call_command('qcluster', '--run-once')
+
+
+def test_qmonitor():
+    call_command('qmonitor', '--run-once')