Increased utils/encoders.py test coverage.

tests/test_encoders.py

-from datetime import date, datetime, timedelta, tzinfo
+from datetime import date, datetime, timedelta
 from decimal import Decimal
 from uuid import uuid4
 
 import pytest
 from django.test import TestCase
+from django.utils.timezone import utc
 
 from rest_framework.compat import coreapi
 from rest_framework.utils.encoders import JSONEncoder
 
 
+class MockList(object):
+    def tolist(self):
+        return [1, 2, 3]
+
+
 class JSONEncoderTests(TestCase):
     """
     Tests the JSONEncoder method
@@ -22,7 +28,7 @@ class JSONEncoderTests(TestCase):
         Tests encoding a decimal
         """
         d = Decimal(3.14)
-        assert d == float(d)
+        assert self.encoder.default(d) == float(d)
 
     def test_encode_datetime(self):
         """
@@ -30,6 +36,8 @@ class JSONEncoderTests(TestCase):
         """
         current_time = datetime.now()
         assert self.encoder.default(current_time) == current_time.isoformat()
+        current_time_utc = current_time.replace(tzinfo=utc)
+        assert self.encoder.default(current_time_utc) == current_time.isoformat() + 'Z'
 
     def test_encode_time(self):
         """
@@ -42,22 +50,8 @@ class JSONEncoderTests(TestCase):
         """
         Tests encoding a timezone aware timestamp
         """
-
-        class UTC(tzinfo):
-            """
-            Class extending tzinfo to mimic UTC time
-            """
-            def utcoffset(self, dt):
-                return timedelta(0)
-
-            def tzname(self, dt):
-                return "UTC"
-
-            def dst(self, dt):
-                return timedelta(0)
-
         current_time = datetime.now().time()
-        current_time = current_time.replace(tzinfo=UTC())
+        current_time = current_time.replace(tzinfo=utc)
         with pytest.raises(ValueError):
             self.encoder.default(current_time)
 
@@ -91,3 +85,10 @@ class JSONEncoderTests(TestCase):
 
         with pytest.raises(RuntimeError):
             self.encoder.default(coreapi.Error())
+
+    def test_encode_object_with_tolist(self):
+        """
+        Tests encoding a object with tolist method
+        """
+        foo = MockList()
+        assert self.encoder.default(foo) == [1, 2, 3]