differences in order_by behaviour

gistfile1.txt

# settings.py

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': 'helloworld',
        'PASSWORD': 'adminhris',
        'USER': 'adminhris',
        'HOST': 'localhost'
    },
    'sql_lite': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': 'test'
    }
}
# -----------------

# models.py


class TestModel(models.Model):
    name = models.CharField(max_length=256)
    age = models.PositiveSmallIntegerField(null=True, blank=True)
    start_date = models.DateTimeField(null=True, blank=True)

# -----------------

from datetime import datetime, timedelta

from django.test import TestCase

from core.models import TestModel


class MyTestCase(TestCase):
    databases = ('default',)

    def setUp(self):
        TestModel.objects.create(name='first', start_date=datetime.today())
        TestModel.objects.create(name='second', start_date=datetime.today() + timedelta(days=10))
        TestModel.objects.create(name='third')

    def test_something_default(self):
        tm = TestModel.objects.using('default').order_by('-start_date')
        self.assertEqual(tm.first().name, 'third')


class MyTestCaseLite(TestCase):
    databases = ('sql_lite',)

    def setUp(self):
        TestModel.objects.using('sql_lite').create(name='first', start_date=datetime.today())
        TestModel.objects.using('sql_lite').create(name='second', start_date=datetime.today() + timedelta(days=10))
        TestModel.objects.using('sql_lite').create(name='third')

    def test_something_sql_lite(self):
        tm = TestModel.objects.using('sql_lite').order_by('-start_date')
        self.assertEqual(tm.first().name, 'second')