from unittest import mock

from django.db import connections

from django.test import TestCase, TransactionTestCase, override_settings

from django.test.testcases import DatabaseOperationForbidden

from .models import Car

class TestSerializedRollbackInhibitsPostMigrate(TransactionTestCase):

    """

    TransactionTestCase._fixture_teardown() inhibits the post_migrate signal

    for test classes with serialized_rollback=True.

    """

    available_apps = ["test_utils"]

    serialized_rollback = True

    def setUp(self):

        # self.available_apps must be None to test the serialized_rollback

        # condition.

        self.available_apps = None

    def tearDown(self):

        self.available_apps = ["test_utils"]

    @mock.patch("django.test.testcases.call_command")

    def test(self, call_command):

        # with a mocked call_command(), this doesn't have any effect.

        self._fixture_teardown()

        call_command.assert_called_with(

            "flush",

            interactive=False,

            allow_cascade=False,

            reset_sequences=False,

            inhibit_post_migrate=True,

            database="default",

            verbosity=0,

        )

@override_settings(DEBUG=True)  # Enable query logging for test_queries_cleared

class TransactionTestCaseDatabasesTests(TestCase):

    available_apps = []

    databases = {"default", "other"}

    def test_queries_cleared(self):

        """

        TransactionTestCase._pre_setup() clears the connections' queries_log

        so that it's less likely to overflow. An overflow causes

        assertNumQueries() to fail.

        """

        for alias in self.databases:

            self.assertEqual(

                len(connections[alias].queries_log), 0, "Failed for alias %s" % alias

            )

class DisallowedDatabaseQueriesTests(TransactionTestCase):

    available_apps = ["test_utils"]

    def test_disallowed_database_queries(self):

        message = (

            "Database queries to 'other' are not allowed in this test. "

            "Add 'other' to test_utils.test_transactiontestcase."

            "DisallowedDatabaseQueriesTests.databases to ensure proper test "

            "isolation and silence this failure."

        )

        with self.assertRaisesMessage(DatabaseOperationForbidden, message):

            Car.objects.using("other").get()