'The test case puts everything under a transaction, so two models
updated with a short gap should have the same time.'

def test_transaction_now(self):

    m1 = NowTestModel.objects.create()
    m2 = NowTestModel.objects.create()
    NowTestModel.objects.filter(id=m1.id).update(when=TransactionNow())
    sleep(0.1)
    NowTestModel.objects.filter(id=m2.id).update(when=TransactionNow())
    m1.refresh_from_db()
    m2.refresh_from_db()
    self.assertIsInstance(m1.when, datetime)
    self.assertEqual(m1.when, m2.when)
