'Test the retrieval of the last payment'

def test_last_payment(self):

    self.assertIsNone(self.transaction.last_payment(True))
    self.assertIsNone(self.transaction.last_payment(False))
    self.transaction.add_payment(self.payment)
    self.assertEqual(self.transaction.last_payment(True), self.payment)
    self.assertEqual(self.transaction.last_payment(False), self.payment)
