def test_is_valid_payment(self):
facture = Facture()
facture.save()
self.assertFalse(facture.is_valid_payment(42))
plat = ProduitVendu()
plat.produit = Produit.objects.get(nom="entrecote")
facture.add_product(plat)
self.assertTrue(facture.is_valid_payment(42))
facture.restant_a_payer = Decimal("0")
self.assertFalse(facture.is_valid_payment(42))
