Add failing TZ tests for DateTimeField

- tests "current" timezone activation
- tests output for non-UTC timezones

requirements/requirements-optionals.txt

@@ -1,4 +1,5 @@
 # Optional packages which may be used with REST framework.
+pytz==2017.2
 markdown==2.6.4
 django-guardian==1.4.8
 django-filter==1.0.4

tests/test_fields.py

@@ -10,12 +10,17 @@ import pytest
 from django.http import QueryDict
 from django.test import TestCase, override_settings
 from django.utils import six
-from django.utils.timezone import utc
+from django.utils.timezone import activate, deactivate, utc
 
 import rest_framework
 from rest_framework import compat, serializers
 from rest_framework.fields import is_simple_callable
 
+try:
+    import pytz
+except ImportError:
+    pytz = None
+
 try:
     import typings
 except ImportError:
@@ -1234,6 +1239,52 @@ class TestNaiveDateTimeField(FieldValues):
     field = serializers.DateTimeField(default_timezone=None)
 
 
+@pytest.mark.skipif(pytz is None, reason='pytz not installed')
+class TestTZWithDateTimeField(FieldValues):
+    """
+    Valid and invalid values for `DateTimeField` when not using UTC as the timezone.
+    """
+    @classmethod
+    def setup_class(cls):
+        # use class setup method, as class-level attribute will still be evaluated even if test is skipped
+        kolkata = pytz.timezone('Asia/Kolkata')
+
+        cls.valid_inputs = {
+            '2016-12-19T10:00:00': kolkata.localize(datetime.datetime(2016, 12, 19, 10)),
+            '2016-12-19T10:00:00+05:30': kolkata.localize(datetime.datetime(2016, 12, 19, 10)),
+            datetime.datetime(2016, 12, 19, 10): kolkata.localize(datetime.datetime(2016, 12, 19, 10)),
+        }
+        cls.invalid_inputs = {}
+        cls.outputs = {
+            datetime.datetime(2016, 12, 19, 10): '2016-12-19T10:00:00+05:30',
+            datetime.datetime(2016, 12, 19, 4, 30, tzinfo=utc): '2016-12-19T10:00:00+05:30',
+        }
+        cls.field = serializers.DateTimeField(default_timezone=kolkata)
+
+
+@pytest.mark.skipif(pytz is None, reason='pytz not installed')
+@override_settings(TIME_ZONE='UTC', USE_TZ=True)
+class TestDefaultTZDateTimeField(TestCase):
+    """
+    Test the current/default timezone handling in `DateTimeField`.
+    """
+
+    @classmethod
+    def setup_class(cls):
+        cls.field = serializers.DateTimeField()
+        cls.kolkata = pytz.timezone('Asia/Kolkata')
+
+    def test_default_timezone(self):
+        assert self.field.default_timezone() == utc
+
+    def test_current_timezone(self):
+        assert self.field.default_timezone() == utc
+        activate(self.kolkata)
+        assert self.field.default_timezone() == self.kolkata
+        deactivate()
+        assert self.field.default_timezone() == utc
+
+
 class TestNaiveDayLightSavingTimeTimeZoneDateTimeField(FieldValues):
     """
     Invalid values for `DateTimeField` with datetime in DST shift (non-existing or ambiguous) and timezone with DST.