import unittest

from migrations.test_base import OperationTestBase, OptimizerTestBase

from django.db import IntegrityError, NotSupportedError, connection, transaction
from django.db.migrations.operations import RemoveIndex, RenameIndex
from django.db.migrations.state import ProjectState
from django.db.migrations.writer import OperationWriter
from django.db.models import CheckConstraint, Index, Q, UniqueConstraint
from django.db.utils import ProgrammingError
from django.test import modify_settings, override_settings
from django.test.utils import CaptureQueriesContext

from . import PostgreSQLTestCase

try:
    from django.contrib.postgres.indexes import BrinIndex, BTreeIndex
    from django.contrib.postgres.operations import (
        AddConstraintNotValid,
        AddIndexConcurrently,
        BloomExtension,
        CreateCollation,
        CreateExtension,
        RemoveCollation,
        RemoveIndexConcurrently,
        ValidateConstraint,
    )
except ImportError:
    pass


@unittest.skipUnless(connection.vendor == "postgresql", "PostgreSQL specific tests.")
@modify_settings(INSTALLED_APPS={"append": "migrations"})
class AddIndexConcurrentlyTests(OptimizerTestBase, OperationTestBase):
    app_label = "test_add_concurrently"

    def test_requires_atomic_false(self):
        project_state = self.set_up_test_model(self.app_label)
        new_state = project_state.clone()
        operation = AddIndexConcurrently(
            "Pony",
            Index(fields=["pink"], name="pony_pink_idx"),
        )
        msg = (
            "The AddIndexConcurrently operation cannot be executed inside "
            "a transaction (set atomic = False on the migration)."
        )
        with self.assertRaisesMessage(NotSupportedError, msg):
            with connection.schema_editor(atomic=True) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )

    def test_add(self):
        project_state = self.set_up_test_model(self.app_label, index=False)
        table_name = "%s_pony" % self.app_label
        index = Index(fields=["pink"], name="pony_pink_idx")
        new_state = project_state.clone()
        operation = AddIndexConcurrently("Pony", index)
        self.assertEqual(
            operation.describe(),
            "Concurrently create index pony_pink_idx on field(s) pink of model Pony",
        )
        self.assertEqual(
            operation.formatted_description(),
            "+ Concurrently create index pony_pink_idx on field(s) pink of model Pony",
        )
        operation.state_forwards(self.app_label, new_state)
        self.assertEqual(
            len(new_state.models[self.app_label, "pony"].options["indexes"]), 1
        )
        self.assertIndexNotExists(table_name, ["pink"])
        # Add index.
        with connection.schema_editor(atomic=False) as editor:
            operation.database_forwards(
                self.app_label, editor, project_state, new_state
            )
        self.assertIndexExists(table_name, ["pink"])
        # Reversal.
        with connection.schema_editor(atomic=False) as editor:
            operation.database_backwards(
                self.app_label, editor, new_state, project_state
            )
        self.assertIndexNotExists(table_name, ["pink"])
        # Deconstruction.
        name, args, kwargs = operation.deconstruct()
        self.assertEqual(name, "AddIndexConcurrently")
        self.assertEqual(args, [])
        self.assertEqual(kwargs, {"model_name": "Pony", "index": index})

    def test_add_other_index_type(self):
        project_state = self.set_up_test_model(self.app_label, index=False)
        table_name = "%s_pony" % self.app_label
        new_state = project_state.clone()
        operation = AddIndexConcurrently(
            "Pony",
            BrinIndex(fields=["pink"], name="pony_pink_brin_idx"),
        )
        self.assertIndexNotExists(table_name, ["pink"])
        # Add index.
        with connection.schema_editor(atomic=False) as editor:
            operation.database_forwards(
                self.app_label, editor, project_state, new_state
            )
        self.assertIndexExists(table_name, ["pink"], index_type="brin")
        # Reversal.
        with connection.schema_editor(atomic=False) as editor:
            operation.database_backwards(
                self.app_label, editor, new_state, project_state
            )
        self.assertIndexNotExists(table_name, ["pink"])

    def test_add_with_options(self):
        project_state = self.set_up_test_model(self.app_label, index=False)
        table_name = "%s_pony" % self.app_label
        new_state = project_state.clone()
        index = BTreeIndex(fields=["pink"], name="pony_pink_btree_idx", fillfactor=70)
        operation = AddIndexConcurrently("Pony", index)
        self.assertIndexNotExists(table_name, ["pink"])
        # Add index.
        with connection.schema_editor(atomic=False) as editor:
            operation.database_forwards(
                self.app_label, editor, project_state, new_state
            )
        self.assertIndexExists(table_name, ["pink"], index_type="btree")
        # Reversal.
        with connection.schema_editor(atomic=False) as editor:
            operation.database_backwards(
                self.app_label, editor, new_state, project_state
            )
        self.assertIndexNotExists(table_name, ["pink"])

    def test_reduce_add_remove_concurrently(self):
        self.assertOptimizesTo(
            [
                AddIndexConcurrently(
                    "Pony",
                    Index(fields=["pink"], name="pony_pink_idx"),
                ),
                RemoveIndex("Pony", "pony_pink_idx"),
            ],
            [],
        )

    def test_reduce_add_remove(self):
        self.assertOptimizesTo(
            [
                AddIndexConcurrently(
                    "Pony",
                    Index(fields=["pink"], name="pony_pink_idx"),
                ),
                RemoveIndexConcurrently("Pony", "pony_pink_idx"),
            ],
            [],
        )

    def test_reduce_add_rename(self):
        self.assertOptimizesTo(
            [
                AddIndexConcurrently(
                    "Pony",
                    Index(fields=["pink"], name="pony_pink_idx"),
                ),
                RenameIndex(
                    "Pony",
                    old_name="pony_pink_idx",
                    new_name="pony_pink_index",
                ),
            ],
            [
                AddIndexConcurrently(
                    "Pony",
                    Index(fields=["pink"], name="pony_pink_index"),
                ),
            ],
        )


@unittest.skipUnless(connection.vendor == "postgresql", "PostgreSQL specific tests.")
@modify_settings(INSTALLED_APPS={"append": "migrations"})
class RemoveIndexConcurrentlyTests(OperationTestBase):
    app_label = "test_rm_concurrently"

    def test_requires_atomic_false(self):
        project_state = self.set_up_test_model(self.app_label, index=True)
        new_state = project_state.clone()
        operation = RemoveIndexConcurrently("Pony", "pony_pink_idx")
        msg = (
            "The RemoveIndexConcurrently operation cannot be executed inside "
            "a transaction (set atomic = False on the migration)."
        )
        with self.assertRaisesMessage(NotSupportedError, msg):
            with connection.schema_editor(atomic=True) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )

    def test_remove(self):
        project_state = self.set_up_test_model(self.app_label, index=True)
        table_name = "%s_pony" % self.app_label
        self.assertTableExists(table_name)
        new_state = project_state.clone()
        operation = RemoveIndexConcurrently("Pony", "pony_pink_idx")
        self.assertEqual(
            operation.describe(),
            "Concurrently remove index pony_pink_idx from Pony",
        )
        self.assertEqual(
            operation.formatted_description(),
            "- Concurrently remove index pony_pink_idx from Pony",
        )
        operation.state_forwards(self.app_label, new_state)
        self.assertEqual(
            len(new_state.models[self.app_label, "pony"].options["indexes"]), 0
        )
        self.assertIndexExists(table_name, ["pink"])
        # Remove index.
        with connection.schema_editor(atomic=False) as editor:
            operation.database_forwards(
                self.app_label, editor, project_state, new_state
            )
        self.assertIndexNotExists(table_name, ["pink"])
        # Reversal.
        with connection.schema_editor(atomic=False) as editor:
            operation.database_backwards(
                self.app_label, editor, new_state, project_state
            )
        self.assertIndexExists(table_name, ["pink"])
        # Deconstruction.
        name, args, kwargs = operation.deconstruct()
        self.assertEqual(name, "RemoveIndexConcurrently")
        self.assertEqual(args, [])
        self.assertEqual(kwargs, {"model_name": "Pony", "name": "pony_pink_idx"})


class NoMigrationRouter:
    def allow_migrate(self, db, app_label, **hints):
        return False


class MigrateWhenHinted:
    def allow_migrate(self, db, app_label, **hints):
        return hints.get("a_hint", False)


@unittest.skipUnless(connection.vendor == "postgresql", "PostgreSQL specific tests.")
class CreateExtensionTests(PostgreSQLTestCase):
    app_label = "test_allow_create_extention"

    @override_settings(DATABASE_ROUTERS=[NoMigrationRouter()])
    def test_no_allow_migrate(self):
        operation = CreateExtension("tablefunc")
        self.assertEqual(
            operation.formatted_description(), "+ Creates extension tablefunc"
        )
        project_state = ProjectState()
        new_state = project_state.clone()
        # Don't create an extension.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 0)
        # Reversal.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_backwards(
                    self.app_label, editor, new_state, project_state
                )
        self.assertEqual(len(captured_queries), 0)

    def test_allow_migrate(self):
        operation = CreateExtension("tablefunc")
        self.assertEqual(
            operation.migration_name_fragment, "create_extension_tablefunc"
        )
        project_state = ProjectState()
        new_state = project_state.clone()
        # Create an extension.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 4)
        self.assertIn("CREATE EXTENSION IF NOT EXISTS", captured_queries[1]["sql"])
        # Reversal.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_backwards(
                    self.app_label, editor, new_state, project_state
                )
        self.assertEqual(len(captured_queries), 2)
        self.assertIn("DROP EXTENSION IF EXISTS", captured_queries[1]["sql"])

    @override_settings(DATABASE_ROUTERS=[MigrateWhenHinted()])
    def test_allow_migrate_based_on_hints(self):
        operation_no_hints = CreateExtension("tablefunc")
        self.assertEqual(operation_no_hints.hints, {})

        operation_hints = CreateExtension("tablefunc", hints={"a_hint": True})
        self.assertEqual(operation_hints.hints, {"a_hint": True})

        project_state = ProjectState()
        new_state = project_state.clone()

        with (
            CaptureQueriesContext(connection) as captured_queries,
            connection.schema_editor(atomic=False) as editor,
        ):
            operation_no_hints.database_forwards(
                self.app_label, editor, project_state, new_state
            )
        self.assertEqual(len(captured_queries), 0)

        with (
            CaptureQueriesContext(connection) as captured_queries,
            connection.schema_editor(atomic=False) as editor,
        ):
            operation_no_hints.database_backwards(
                self.app_label, editor, project_state, new_state
            )
        self.assertEqual(len(captured_queries), 0)

        with (
            CaptureQueriesContext(connection) as captured_queries,
            connection.schema_editor(atomic=False) as editor,
        ):
            operation_hints.database_forwards(
                self.app_label, editor, project_state, new_state
            )
        self.assertEqual(len(captured_queries), 4)
        self.assertIn("CREATE EXTENSION IF NOT EXISTS", captured_queries[1]["sql"])

        with (
            CaptureQueriesContext(connection) as captured_queries,
            connection.schema_editor(atomic=False) as editor,
        ):
            operation_hints.database_backwards(
                self.app_label, editor, project_state, new_state
            )
        self.assertEqual(len(captured_queries), 2)
        self.assertIn("DROP EXTENSION IF EXISTS", captured_queries[1]["sql"])

    def test_create_existing_extension(self):
        operation = BloomExtension()
        self.assertEqual(operation.migration_name_fragment, "create_extension_bloom")
        project_state = ProjectState()
        new_state = project_state.clone()
        # Don't create an existing extension.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 3)
        self.assertIn("SELECT", captured_queries[0]["sql"])

    def test_drop_nonexistent_extension(self):
        operation = CreateExtension("tablefunc")
        project_state = ProjectState()
        new_state = project_state.clone()
        # Don't drop a nonexistent extension.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_backwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("SELECT", captured_queries[0]["sql"])


@unittest.skipUnless(connection.vendor == "postgresql", "PostgreSQL specific tests.")
class CreateCollationTests(OptimizerTestBase, PostgreSQLTestCase):
    app_label = "test_allow_create_collation"

    @override_settings(DATABASE_ROUTERS=[NoMigrationRouter()])
    def test_no_allow_migrate(self):
        operation = CreateCollation("C_test", locale="C")
        project_state = ProjectState()
        new_state = project_state.clone()
        # Don't create a collation.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 0)
        # Reversal.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_backwards(
                    self.app_label, editor, new_state, project_state
                )
        self.assertEqual(len(captured_queries), 0)

    def test_create(self):
        operation = CreateCollation("C_test", locale="C")
        self.assertEqual(operation.migration_name_fragment, "create_collation_c_test")
        self.assertEqual(operation.describe(), "Create collation C_test")
        self.assertEqual(operation.formatted_description(), "+ Create collation C_test")
        project_state = ProjectState()
        new_state = project_state.clone()
        # Create a collation.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("CREATE COLLATION", captured_queries[0]["sql"])
        # Creating the same collation raises an exception.
        with self.assertRaisesMessage(ProgrammingError, "already exists"):
            with connection.schema_editor(atomic=True) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        # Reversal.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_backwards(
                    self.app_label, editor, new_state, project_state
                )
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("DROP COLLATION", captured_queries[0]["sql"])
        # Deconstruction.
        name, args, kwargs = operation.deconstruct()
        self.assertEqual(name, "CreateCollation")
        self.assertEqual(args, [])
        self.assertEqual(kwargs, {"name": "C_test", "locale": "C"})

    def test_create_non_deterministic_collation(self):
        operation = CreateCollation(
            "case_insensitive_test",
            "und-u-ks-level2",
            provider="icu",
            deterministic=False,
        )
        project_state = ProjectState()
        new_state = project_state.clone()
        # Create a collation.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("CREATE COLLATION", captured_queries[0]["sql"])
        # Reversal.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_backwards(
                    self.app_label, editor, new_state, project_state
                )
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("DROP COLLATION", captured_queries[0]["sql"])
        # Deconstruction.
        name, args, kwargs = operation.deconstruct()
        self.assertEqual(name, "CreateCollation")
        self.assertEqual(args, [])
        self.assertEqual(
            kwargs,
            {
                "name": "case_insensitive_test",
                "locale": "und-u-ks-level2",
                "provider": "icu",
                "deterministic": False,
            },
        )

    def test_create_collation_alternate_provider(self):
        operation = CreateCollation(
            "german_phonebook_test",
            provider="icu",
            locale="de-u-co-phonebk",
        )
        project_state = ProjectState()
        new_state = project_state.clone()
        # Create an collation.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("CREATE COLLATION", captured_queries[0]["sql"])
        # Reversal.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_backwards(
                    self.app_label, editor, new_state, project_state
                )
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("DROP COLLATION", captured_queries[0]["sql"])

    def test_writer(self):
        operation = CreateCollation(
            "sample_collation",
            "und-u-ks-level2",
            provider="icu",
            deterministic=False,
        )
        buff, imports = OperationWriter(operation, indentation=0).serialize()
        self.assertEqual(imports, {"import django.contrib.postgres.operations"})
        self.assertEqual(
            buff,
            "django.contrib.postgres.operations.CreateCollation(\n"
            "    name='sample_collation',\n"
            "    locale='und-u-ks-level2',\n"
            "    provider='icu',\n"
            "    deterministic=False,\n"
            "),",
        )

    def test_reduce_create_remove(self):
        self.assertOptimizesTo(
            [
                CreateCollation(
                    "sample_collation",
                    "und-u-ks-level2",
                    provider="icu",
                    deterministic=False,
                ),
                RemoveCollation(
                    "sample_collation",
                    # Different locale
                    "de-u-ks-level1",
                ),
            ],
            [],
        )


@unittest.skipUnless(connection.vendor == "postgresql", "PostgreSQL specific tests.")
class RemoveCollationTests(PostgreSQLTestCase):
    app_label = "test_allow_remove_collation"

    @override_settings(DATABASE_ROUTERS=[NoMigrationRouter()])
    def test_no_allow_migrate(self):
        operation = RemoveCollation("C_test", locale="C")
        project_state = ProjectState()
        new_state = project_state.clone()
        # Don't create a collation.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 0)
        # Reversal.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_backwards(
                    self.app_label, editor, new_state, project_state
                )
        self.assertEqual(len(captured_queries), 0)

    def test_remove(self):
        operation = CreateCollation("C_test", locale="C")
        project_state = ProjectState()
        new_state = project_state.clone()
        with connection.schema_editor(atomic=False) as editor:
            operation.database_forwards(
                self.app_label, editor, project_state, new_state
            )

        operation = RemoveCollation("C_test", locale="C")
        self.assertEqual(operation.migration_name_fragment, "remove_collation_c_test")
        self.assertEqual(operation.describe(), "Remove collation C_test")
        self.assertEqual(operation.formatted_description(), "- Remove collation C_test")
        project_state = ProjectState()
        new_state = project_state.clone()
        # Remove a collation.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("DROP COLLATION", captured_queries[0]["sql"])
        # Removing a nonexistent collation raises an exception.
        with self.assertRaisesMessage(ProgrammingError, "does not exist"):
            with connection.schema_editor(atomic=True) as editor:
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        # Reversal.
        with CaptureQueriesContext(connection) as captured_queries:
            with connection.schema_editor(atomic=False) as editor:
                operation.database_backwards(
                    self.app_label, editor, new_state, project_state
                )
        self.assertEqual(len(captured_queries), 1)
        self.assertIn("CREATE COLLATION", captured_queries[0]["sql"])
        # Deconstruction.
        name, args, kwargs = operation.deconstruct()
        self.assertEqual(name, "RemoveCollation")
        self.assertEqual(args, [])
        self.assertEqual(kwargs, {"name": "C_test", "locale": "C"})


@unittest.skipUnless(connection.vendor == "postgresql", "PostgreSQL specific tests.")
@modify_settings(INSTALLED_APPS={"append": "migrations"})
class AddConstraintNotValidTests(OperationTestBase):
    app_label = "test_add_constraint_not_valid"

    def test_non_check_constraint_not_supported(self):
        constraint = UniqueConstraint(fields=["pink"], name="pony_pink_uniq")
        msg = "AddConstraintNotValid.constraint must be a check constraint."
        with self.assertRaisesMessage(TypeError, msg):
            AddConstraintNotValid(model_name="pony", constraint=constraint)

    def test_add(self):
        table_name = f"{self.app_label}_pony"
        constraint_name = "pony_pink_gte_check"
        constraint = CheckConstraint(condition=Q(pink__gte=4), name=constraint_name)
        operation = AddConstraintNotValid("Pony", constraint=constraint)
        project_state, new_state = self.make_test_state(self.app_label, operation)
        self.assertEqual(
            operation.describe(),
            f"Create not valid constraint {constraint_name} on model Pony",
        )
        self.assertEqual(
            operation.formatted_description(),
            f"+ Create not valid constraint {constraint_name} on model Pony",
        )
        self.assertEqual(
            operation.migration_name_fragment,
            f"pony_{constraint_name}_not_valid",
        )
        self.assertEqual(
            len(new_state.models[self.app_label, "pony"].options["constraints"]),
            1,
        )
        self.assertConstraintNotExists(table_name, constraint_name)
        Pony = new_state.apps.get_model(self.app_label, "Pony")
        self.assertEqual(len(Pony._meta.constraints), 1)
        Pony.objects.create(pink=2, weight=1.0)
        # Add constraint.
        with connection.schema_editor(atomic=True) as editor:
            operation.database_forwards(
                self.app_label, editor, project_state, new_state
            )
        msg = f'check constraint "{constraint_name}"'
        with self.assertRaisesMessage(IntegrityError, msg), transaction.atomic():
            Pony.objects.create(pink=3, weight=1.0)
        self.assertConstraintExists(table_name, constraint_name)
        # Reversal.
        with connection.schema_editor(atomic=True) as editor:
            operation.database_backwards(
                self.app_label, editor, project_state, new_state
            )
        self.assertConstraintNotExists(table_name, constraint_name)
        Pony.objects.create(pink=3, weight=1.0)
        # Deconstruction.
        name, args, kwargs = operation.deconstruct()
        self.assertEqual(name, "AddConstraintNotValid")
        self.assertEqual(args, [])
        self.assertEqual(kwargs, {"model_name": "Pony", "constraint": constraint})


@unittest.skipUnless(connection.vendor == "postgresql", "PostgreSQL specific tests.")
@modify_settings(INSTALLED_APPS={"append": "migrations"})
class ValidateConstraintTests(OperationTestBase):
    app_label = "test_validate_constraint"

    def test_validate(self):
        constraint_name = "pony_pink_gte_check"
        constraint = CheckConstraint(condition=Q(pink__gte=4), name=constraint_name)
        operation = AddConstraintNotValid("Pony", constraint=constraint)
        project_state, new_state = self.make_test_state(self.app_label, operation)
        Pony = new_state.apps.get_model(self.app_label, "Pony")
        obj = Pony.objects.create(pink=2, weight=1.0)
        # Add constraint.
        with connection.schema_editor(atomic=True) as editor:
            operation.database_forwards(
                self.app_label, editor, project_state, new_state
            )
        project_state = new_state
        new_state = new_state.clone()
        operation = ValidateConstraint("Pony", name=constraint_name)
        operation.state_forwards(self.app_label, new_state)
        self.assertEqual(
            operation.describe(),
            f"Validate constraint {constraint_name} on model Pony",
        )
        self.assertEqual(
            operation.formatted_description(),
            f"~ Validate constraint {constraint_name} on model Pony",
        )
        self.assertEqual(
            operation.migration_name_fragment,
            f"pony_validate_{constraint_name}",
        )
        # Validate constraint.
        with connection.schema_editor(atomic=True) as editor:
            msg = f'check constraint "{constraint_name}"'
            with self.assertRaisesMessage(IntegrityError, msg):
                operation.database_forwards(
                    self.app_label, editor, project_state, new_state
                )
        obj.pink = 5
        obj.save()
        with connection.schema_editor(atomic=True) as editor:
            operation.database_forwards(
                self.app_label, editor, project_state, new_state
            )
        # Reversal is a noop.
        with connection.schema_editor() as editor:
            with self.assertNumQueries(0):
                operation.database_backwards(
                    self.app_label, editor, new_state, project_state
                )
        # Deconstruction.
        name, args, kwargs = operation.deconstruct()
        self.assertEqual(name, "ValidateConstraint")
        self.assertEqual(args, [])
        self.assertEqual(kwargs, {"model_name": "Pony", "name": constraint_name})
