Add tests for Relation queries

Making an Object, and then marking that it's got Relation's doesn't
work. These tests demonstrate that. Next commit will fix whatever's
needed so that these tests pass.

parse_rest/tests.py

@@ -59,6 +59,14 @@ class GameScore(Object):
     pass
 
 
+class GameMap(Object):
+    pass
+
+
+class GameMode(Object):
+    pass
+
+
 class City(Object):
     pass
 
@@ -348,6 +356,25 @@ class TestQuery(unittest.TestCase):
         self.assertEqual(GameScore.Query.filter(createdAt__lte=tomorrow).count(), 5,
                          'Could not make inequality comparison with dates')
 
+    def testRelations(self):
+        """Make some maps, make a Game Mode that has many maps, find all maps
+        given a Game Mode"""
+        maps = [GameMap(name="map " + i) for i in ['a', 'b', 'c', 'd']]
+        ParseBatcher().batch_save(maps)
+
+        gm = GameMode(name='test mode')
+        gm.save()
+        gm.addRelation("maps", GameMap.__name__, [m.objectId for m in maps])
+
+        modes = GameMode.Query.all()
+        self.assertEqual(len(modes), 1)
+        mode = modes[0]
+        maps_for_mode = GameMap.Query.filter(maps__relatedTo=mode)
+        self.assertEqual(len(maps_for_mode), 4)
+
+        gm.delete()
+        ParseBatcher().batch_delete(maps)
+
 
 class TestFunction(unittest.TestCase):
     def setUp(self):