add tutoringgroups view to tutor api

oser_cs/tests/test_api/test_tutor_api.py

 """Tutor API tests."""
-from users.serializers import TutorSerializer
-from tests.factory import TutorFactory
-from tests.utils.api import HyperlinkedAPITestCase
+from rest_framework import status
+from tests.factory import TutorFactory, TutorTutoringGroupFactory
 from tests.test_api.mixins import ProfileEndpointsTestMixin
+from tests.utils.api import HyperlinkedAPITestCase
+
+from users.serializers import TutorSerializer
 
 
 class TutorEndpointsTest(ProfileEndpointsTestMixin, HyperlinkedAPITestCase):
@@ -54,3 +56,15 @@ class TutorEndpointsTest(ProfileEndpointsTestMixin, HyperlinkedAPITestCase):
         url = '/api/tutors/{obj.pk}/'.format(obj=obj)
         response = self.client.delete(url)
         return response
+
+    def test_list_tutoring_groups(self):
+        def perform_list_tutoring_groups():
+            obj = self.factory.create()
+            # add tutor to several tutoring groups
+            TutorTutoringGroupFactory.create_batch(3, tutor=obj)
+            url = '/api/tutors/{}/tutoringgroups/'.format(obj.pk)
+            response = self.client.get(url)
+            return response
+
+        self.assertRequiresAuth(perform_list_tutoring_groups,
+                                expected_status_code=status.HTTP_200_OK)

oser_cs/users/views.py

@@ -98,6 +98,15 @@ class TutorViewSet(ProfileViewSet):
     queryset = Tutor.objects.all()
     serializer_class = TutorSerializer
 
+    @detail_route()
+    def tutoringgroups(self, request, pk=None):
+        """Retrieve the tutoring groups of a tutor."""
+        tutor = self.get_object()
+        tutoring_groups = tutor.tutoring_groups.all()
+        serializer = TutoringGroupSerializer(tutoring_groups, many=True,
+                                             context={'request': request})
+        return Response(serializer.data)
+
 
 class StudentViewSet(ProfileViewSet):
     """API endpoint that allows students to be viewed or edited."""