Add test for serialize/deserialize.

common/lib/xmodule/xmodule/tests/test_fields.py

@@ -78,3 +78,18 @@ class DateTest(unittest.TestCase):
                 DateTest.date.from_json("2012-12-31T23:00:01-01:00")),
             "2013-01-01T00:00:01Z")
 
+    def test_serialize(self):
+        self.assertEqual(
+            DateTest.date.serialize("2012-12-31T23:59:59Z"),
+            '"2012-12-31T23:59:59Z"'
+        )
+
+    def test_deserialize(self):
+        self.assertEqual(
+            '2012-12-31T23:59:59Z',
+            DateTest.date.deserialize("2012-12-31T23:59:59Z"),
+        )
+        self.assertEqual(
+            '2012-12-31T23:59:59Z',
+            DateTest.date.deserialize('"2012-12-31T23:59:59Z"'),
+        )