'Create a serializer with the given data, ensure that it is valid, save
the result, and return the full comment data from the serializer.'

def save_and_reserialize(self, data, instance=None):

    context = get_context(self.course, self.request, make_minimal_cs_thread({'course_id': unicode(self.course.id)}))
    serializer = CommentSerializer(instance, data=data, partial=(instance is not None), context=context)
    self.assertTrue(serializer.is_valid())
    serializer.save()
    return serializer.data
