Fixed #11964 -- Added support for database check constraints.

tests/constraints/tests.py

@@ -0,0 +1,30 @@
+from django.db import IntegrityError, models
+from django.test import TestCase, skipUnlessDBFeature
+
+from .models import Product
+
+
+class CheckConstraintTests(TestCase):
+    def test_repr(self):
+        constraint = models.Q(price__gt=models.F('discounted_price'))
+        name = 'price_gt_discounted_price'
+        check = models.CheckConstraint(constraint, name)
+        self.assertEqual(
+            repr(check),
+            "<CheckConstraint: constraint='{}' name='{}'>".format(constraint, name),
+        )
+
+    def test_deconstruction(self):
+        constraint = models.Q(price__gt=models.F('discounted_price'))
+        name = 'price_gt_discounted_price'
+        check = models.CheckConstraint(constraint, name)
+        path, args, kwargs = check.deconstruct()
+        self.assertEqual(path, 'django.db.models.CheckConstraint')
+        self.assertEqual(args, ())
+        self.assertEqual(kwargs, {'constraint': constraint, 'name': name})
+
+    @skipUnlessDBFeature('supports_table_check_constraints')
+    def test_model_constraint(self):
+        Product.objects.create(name='Valid', price=10, discounted_price=5)
+        with self.assertRaises(IntegrityError):
+            Product.objects.create(name='Invalid', price=10, discounted_price=20)