How can I test dates and datetimes in different formats?

Question

I have a web app that I am unit testing. I'm trying to test the drf serializers, but the serializers change the format of datetimes, so identical dates formatted differently are failing the test because they're not identical.

I've tried formatting the serializer timeDateField, but all of the strftime formats they use are zero-padded, and my test Users last-login attribute gives the date without zero-padding. I think the solution could be solved the way that the selected answer describes here but that seems a bit sketchy, and ideally, I, as someone who will have to maintain this code, want a cleaner or more pythonic solution.

Here is the test:

class UserTest(TestCase):

    def setup(self):

        last_login = datetime.datetime(2000, 1, 1, hour=0, minute=0, second=0, microsecond=0, tzinfo=None)
        date_joined = datetime.datetime(2019, 2, 2, hour=2, minute=2, second=2, microsecond=2, tzinfo=None)
        birthdate = timezone.now().date()
        renewal = timezone.now().date()

        return User.objects.create(username='test_user', first_name='test_first', last_name='test_last',
                                   email='test_mail', last_login=last_login, date_joined=date_joined,
                                   birthdate=birthdate, gender='U', renewal=renewal)

    def test_user_serializer(self):
        self.u = self.setup()
        serializer = UserSerializer(self.u, many=False)
        data = serializer.data
              .....
    # tests for serialized attributes
        self.assertEquals((data['last_login']), self.u.last_login)  # FAILING THE TEST

Here is the UserSerializer:

class UserSerializer(serializers.ModelSerializer):

    last_login = serializers.DateTimeField
    date_joined = serializers.DateTimeField
    birthdate = serializers.DateField
    renewal = serializers.DateField

    class Meta:
        model = User
        fields = ('__all__')

Here is the error I am getting:

self.assertEquals(data['last_login'], self.u.last_login)
AssertionError: '2000-01-01T00:00:00Z' != datetime.datetime(2000, 1, 1, 0, 0)

In the model, the last_login attribute is a dateTimeField.

Should I be trying to change the formats of one of the elements being tested or is there a way to write a test that compares the dates irrespective of format?

Please advise. Thank you.

Answer 1

The simplest way to do that is:

assert response.json()["created_at"] == serializers.DateTimeField().to_representation(instance.created_at)

Answer 2

Some modifications to Vasu Deo.S's answer which include microsecond in the formatting.

import datetime

datet_obj = datetime.datetime(2000, 1, 1, 0, 0)

datet_str = datet_obj.strftime("%Y-%m-%dT%H:%M:%S.%fZ")

print(datet_str)

Output

2000-01-01T00:00:00.000000Z