Refs #34553 -- Split constraint escaping test in subtests.

This ensures that constraint violations are tested in isolation from
each other as an IntegrityError only ensures a least one constraint is
violated.

For example, the assertion added in 42e8cf4 break both the
name_constraint_rhs and the rebate_constraint constraints and thus
doesn't constitute a proper regression test. Refs #32369.

tests/migrations/test_operations.py

@@ -3652,47 +3652,44 @@ def test_add_constraint_percent_escaping(self):
             ),
         ]
         from_state = self.apply_operations(app_label, ProjectState(), operations)
-        # "%" generated in startswith lookup should be escaped in a way that is
-        # considered a leading wildcard.
-        check = models.Q(name__startswith="Albert")
-        constraint = models.CheckConstraint(check=check, name="name_constraint")
-        operation = migrations.AddConstraint("Author", constraint)
-        to_state = from_state.clone()
-        operation.state_forwards(app_label, to_state)
-        with connection.schema_editor() as editor:
-            operation.database_forwards(app_label, editor, from_state, to_state)
-        Author = to_state.apps.get_model(app_label, "Author")
-        with self.assertRaises(IntegrityError), transaction.atomic():
-            Author.objects.create(name="Artur")
-        # Literal "%" should be escaped in a way that is not a considered a
-        # wildcard.
-        check = models.Q(rebate__endswith="%")
-        constraint = models.CheckConstraint(check=check, name="rebate_constraint")
-        operation = migrations.AddConstraint("Author", constraint)
-        from_state = to_state
-        to_state = from_state.clone()
-        operation.state_forwards(app_label, to_state)
-        Author = to_state.apps.get_model(app_label, "Author")
-        with connection.schema_editor() as editor:
-            operation.database_forwards(app_label, editor, from_state, to_state)
-        Author = to_state.apps.get_model(app_label, "Author")
-        with self.assertRaises(IntegrityError), transaction.atomic():
-            Author.objects.create(name="Albert", rebate="10$")
-        author = Author.objects.create(name="Albert", rebate="10%")
-        self.assertEqual(Author.objects.get(), author)
-        # Right-hand-side baked "%" literals should not be used for parameters
-        # interpolation.
-        check = ~models.Q(surname__startswith=models.F("name"))
-        constraint = models.CheckConstraint(check=check, name="name_constraint_rhs")
-        operation = migrations.AddConstraint("Author", constraint)
-        from_state = to_state
-        to_state = from_state.clone()
-        operation.state_forwards(app_label, to_state)
-        with connection.schema_editor() as editor:
-            operation.database_forwards(app_label, editor, from_state, to_state)
-        Author = to_state.apps.get_model(app_label, "Author")
-        with self.assertRaises(IntegrityError), transaction.atomic():
-            Author.objects.create(name="Albert", surname="Alberto")
+        checks = [
+            # "%" generated in startswith lookup should be escaped in a way
+            # that is considered a leading wildcard.
+            (
+                models.Q(name__startswith="Albert"),
+                {"name": "Alberta"},
+                {"name": "Artur"},
+            ),
+            # Literal "%" should be escaped in a way that is not a considered a
+            # wildcard.
+            (models.Q(rebate__endswith="%"), {"rebate": "10%"}, {"rebate": "10$"}),
+            # Right-hand-side baked "%" literals should not be used for
+            # parameters interpolation.
+            (
+                ~models.Q(surname__startswith=models.F("name")),
+                {"name": "Albert"},
+                {"name": "Albert", "surname": "Alberto"},
+            ),
+        ]
+        for check, valid, invalid in checks:
+            with self.subTest(check=check, valid=valid, invalid=invalid):
+                constraint = models.CheckConstraint(check=check, name="constraint")
+                operation = migrations.AddConstraint("Author", constraint)
+                to_state = from_state.clone()
+                operation.state_forwards(app_label, to_state)
+                with connection.schema_editor() as editor:
+                    operation.database_forwards(app_label, editor, from_state, to_state)
+                Author = to_state.apps.get_model(app_label, "Author")
+                try:
+                    with transaction.atomic():
+                        Author.objects.create(**valid).delete()
+                    with self.assertRaises(IntegrityError), transaction.atomic():
+                        Author.objects.create(**invalid)
+                finally:
+                    with connection.schema_editor() as editor:
+                        operation.database_backwards(
+                            app_label, editor, from_state, to_state
+                        )
 
     @skipUnlessDBFeature("supports_table_check_constraints")
     def test_add_or_constraint(self):