Refs #31117 -- Made various tests properly handle unexpected databases aliases.

- Used selected "databases" instead of django.db.connections.
- Made routers in tests.migrations skip migrations on unexpected
  databases.
- Added DiscoverRunnerGetDatabasesTests.assertSkippedDatabases() hook
  which properly asserts messages about skipped databases.

9 files changed, 46 insertions, 34 deletions

diff --git a/tests/admin_views/test_multidb.py b/tests/admin_views/test_multidb.py
index a02b637d34..7ff1f7f663 100644
--- a/tests/admin_views/test_multidb.py
+++ b/tests/admin_views/test_multidb.py
@@ -2,7 +2,6 @@ from unittest import mock
 
 from django.contrib import admin
 from django.contrib.auth.models import User
-from django.db import connections
 from django.test import TestCase, override_settings
 from django.urls import path, reverse
 
@@ -34,7 +33,7 @@ class MultiDatabaseTests(TestCase):
     def setUpTestData(cls):
         cls.superusers = {}
         cls.test_book_ids = {}
-        for db in connections:
+        for db in cls.databases:
             Router.target_db = db
             cls.superusers[db] = User.objects.create_superuser(
                 username='admin', password='something', email='test@test.org',
@@ -45,7 +44,7 @@ class MultiDatabaseTests(TestCase):
 
     @mock.patch('django.contrib.admin.options.transaction')
     def test_add_view(self, mock):
-        for db in connections:
+        for db in self.databases:
             with self.subTest(db=db):
                 Router.target_db = db
                 self.client.force_login(self.superusers[db])
@@ -57,7 +56,7 @@ class MultiDatabaseTests(TestCase):
 
     @mock.patch('django.contrib.admin.options.transaction')
     def test_change_view(self, mock):
-        for db in connections:
+        for db in self.databases:
             with self.subTest(db=db):
                 Router.target_db = db
                 self.client.force_login(self.superusers[db])
@@ -69,7 +68,7 @@ class MultiDatabaseTests(TestCase):
 
     @mock.patch('django.contrib.admin.options.transaction')
     def test_delete_view(self, mock):
-        for db in connections:
+        for db in self.databases:
             with self.subTest(db=db):
                 Router.target_db = db
                 self.client.force_login(self.superusers[db])
diff --git a/tests/auth_tests/test_admin_multidb.py b/tests/auth_tests/test_admin_multidb.py
index 5849ef98e5..fac2c0fc7e 100644
--- a/tests/auth_tests/test_admin_multidb.py
+++ b/tests/auth_tests/test_admin_multidb.py
@@ -3,7 +3,6 @@ from unittest import mock
 from django.contrib import admin
 from django.contrib.auth.admin import UserAdmin
 from django.contrib.auth.models import User
-from django.db import connections
 from django.test import TestCase, override_settings
 from django.urls import path, reverse
 
@@ -32,7 +31,7 @@ class MultiDatabaseTests(TestCase):
     @classmethod
     def setUpTestData(cls):
         cls.superusers = {}
-        for db in connections:
+        for db in cls.databases:
             Router.target_db = db
             cls.superusers[db] = User.objects.create_superuser(
                 username='admin', password='something', email='test@test.org',
@@ -40,7 +39,7 @@ class MultiDatabaseTests(TestCase):
 
     @mock.patch('django.contrib.auth.admin.transaction')
     def test_add_view(self, mock):
-        for db in connections:
+        for db in self.databases:
             with self.subTest(db_connection=db):
                 Router.target_db = db
                 self.client.force_login(self.superusers[db])
diff --git a/tests/backends/tests.py b/tests/backends/tests.py
index da20d94442..918fc32166 100644
--- a/tests/backends/tests.py
+++ b/tests/backends/tests.py
@@ -687,11 +687,15 @@ class ThreadTests(TransactionTestCase):
                 conn.inc_thread_sharing()
                 connections_dict[id(conn)] = conn
         try:
-            for x in range(2):
+            num_new_threads = 2
+            for x in range(num_new_threads):
                 t = threading.Thread(target=runner)
                 t.start()
                 t.join()
-            self.assertEqual(len(connections_dict), 6)
+            self.assertEqual(
+                len(connections_dict),
+                len(connections.all()) * (num_new_threads + 1),
+            )
         finally:
             # Finish by closing the connections opened by the other threads
             # (the connection opened in the main thread will automatically be
diff --git a/tests/migrations/routers.py b/tests/migrations/routers.py
index 21dfc561bd..bc036382a7 100644
--- a/tests/migrations/routers.py
+++ b/tests/migrations/routers.py
@@ -1,5 +1,6 @@
-class EmptyRouter:
-    pass
+class DefaultOtherRouter:
+    def allow_migrate(self, db, app_label, model_name=None, **hints):
+        return db in {'default', 'other'}
 
 
 class TestRouter:
@@ -9,5 +10,5 @@ class TestRouter:
         """
         if model_name == 'tribble':
             return db == 'other'
-        elif db == 'other':
+        elif db != 'default':
             return False
diff --git a/tests/migrations/test_base.py b/tests/migrations/test_base.py
index 45c5472b0f..c4c8b1ee6c 100644
--- a/tests/migrations/test_base.py
+++ b/tests/migrations/test_base.py
@@ -24,7 +24,7 @@ class MigrationTestBase(TransactionTestCase):
 
     def tearDown(self):
         # Reset applied-migrations state.
-        for db in connections:
+        for db in self.databases:
             recorder = MigrationRecorder(connections[db])
             recorder.migration_qs.filter(app='migrations').delete()
 
diff --git a/tests/migrations/test_commands.py b/tests/migrations/test_commands.py
index 5f57dc7cad..b98b77cd99 100644
--- a/tests/migrations/test_commands.py
+++ b/tests/migrations/test_commands.py
@@ -129,7 +129,7 @@ class MigrateTests(MigrationTestBase):
         that check.
         """
         # Make sure no tables are created
-        for db in connections:
+        for db in self.databases:
             self.assertTableNotExists("migrations_author", using=db)
             self.assertTableNotExists("migrations_tribble", using=db)
         # Run the migrations to 0001 only
@@ -192,7 +192,7 @@ class MigrateTests(MigrationTestBase):
         call_command("migrate", "migrations", "zero", verbosity=0)
         call_command("migrate", "migrations", "zero", verbosity=0, database="other")
         # Make sure it's all gone
-        for db in connections:
+        for db in self.databases:
             self.assertTableNotExists("migrations_author", using=db)
             self.assertTableNotExists("migrations_tribble", using=db)
             self.assertTableNotExists("migrations_book", using=db)
@@ -931,7 +931,7 @@ class MakeMigrationsTests(MigrationTestBase):
 
                 # With a router that doesn't prohibit migrating 'other',
                 # consistency is checked.
-                with self.settings(DATABASE_ROUTERS=['migrations.routers.EmptyRouter']):
+                with self.settings(DATABASE_ROUTERS=['migrations.routers.DefaultOtherRouter']):
                     with self.assertRaisesMessage(Exception, 'Other connection'):
                         call_command('makemigrations', 'migrations', verbosity=0)
                 self.assertEqual(has_table.call_count, 4)  # 'default' and 'other'
@@ -944,12 +944,14 @@ class MakeMigrationsTests(MigrationTestBase):
                 allow_migrate.assert_any_call('other', 'migrations', model_name='UnicodeModel')
                 # allow_migrate() is called with the correct arguments.
                 self.assertGreater(len(allow_migrate.mock_calls), 0)
+                called_aliases = set()
                 for mock_call in allow_migrate.mock_calls:
                     _, call_args, call_kwargs = mock_call
                     connection_alias, app_name = call_args
-                    self.assertIn(connection_alias, ['default', 'other'])
+                    called_aliases.add(connection_alias)
                     # Raises an error if invalid app_name/model_name occurs.
                     apps.get_app_config(app_name).get_model(call_kwargs['model_name'])
+                self.assertEqual(called_aliases, set(connections))
                 self.assertEqual(has_table.call_count, 4)
 
     def test_failing_migration(self):
diff --git a/tests/multiple_database/tests.py b/tests/multiple_database/tests.py
index e39967ce78..2a6a725472 100644
--- a/tests/multiple_database/tests.py
+++ b/tests/multiple_database/tests.py
@@ -7,7 +7,7 @@ from unittest.mock import Mock
 from django.contrib.auth.models import User
 from django.contrib.contenttypes.models import ContentType
 from django.core import management
-from django.db import DEFAULT_DB_ALIAS, connections, router, transaction
+from django.db import DEFAULT_DB_ALIAS, router, transaction
 from django.db.models import signals
 from django.db.utils import ConnectionRouter
 from django.test import SimpleTestCase, TestCase, override_settings
@@ -1632,7 +1632,7 @@ class PickleQuerySetTestCase(TestCase):
     databases = {'default', 'other'}
 
     def test_pickling(self):
-        for db in connections:
+        for db in self.databases:
             Book.objects.using(db).create(title='Dive into Python', published=datetime.date(2009, 5, 4))
             qs = Book.objects.all()
             self.assertEqual(qs.db, pickle.loads(pickle.dumps(qs)).db)
diff --git a/tests/test_runner/test_discover_runner.py b/tests/test_runner/test_discover_runner.py
index 186dc52a44..61af22d818 100644
--- a/tests/test_runner/test_discover_runner.py
+++ b/tests/test_runner/test_discover_runner.py
@@ -308,6 +308,15 @@ class DiscoverRunnerGetDatabasesTests(SimpleTestCase):
             databases = self.runner.get_databases(suite)
         return databases, stdout.getvalue()
 
+    def assertSkippedDatabases(self, test_labels, expected_databases):
+        databases, output = self.get_databases(test_labels)
+        self.assertEqual(databases, expected_databases)
+        skipped_databases = set(connections) - expected_databases
+        if skipped_databases:
+            self.assertIn(self.skip_msg + ', '.join(sorted(skipped_databases)), output)
+        else:
+            self.assertNotIn(self.skip_msg, output)
+
     def test_mixed(self):
         databases, output = self.get_databases(['test_runner_apps.databases.tests'])
         self.assertEqual(databases, set(connections))
@@ -319,24 +328,22 @@ class DiscoverRunnerGetDatabasesTests(SimpleTestCase):
         self.assertNotIn(self.skip_msg, output)
 
     def test_default_and_other(self):
-        databases, output = self.get_databases([
+        self.assertSkippedDatabases([
             'test_runner_apps.databases.tests.DefaultDatabaseTests',
             'test_runner_apps.databases.tests.OtherDatabaseTests',
-        ])
-        self.assertEqual(databases, set(connections))
-        self.assertNotIn(self.skip_msg, output)
+        ], {'default', 'other'})
 
     def test_default_only(self):
-        databases, output = self.get_databases(['test_runner_apps.databases.tests.DefaultDatabaseTests'])
-        self.assertEqual(databases, {'default'})
-        self.assertIn(self.skip_msg + 'other', output)
+        self.assertSkippedDatabases([
+            'test_runner_apps.databases.tests.DefaultDatabaseTests',
+        ], {'default'})
 
     def test_other_only(self):
-        databases, output = self.get_databases(['test_runner_apps.databases.tests.OtherDatabaseTests'])
-        self.assertEqual(databases, {'other'})
-        self.assertIn(self.skip_msg + 'default', output)
+        self.assertSkippedDatabases([
+            'test_runner_apps.databases.tests.OtherDatabaseTests'
+        ], {'other'})
 
     def test_no_databases_required(self):
-        databases, output = self.get_databases(['test_runner_apps.databases.tests.NoDatabaseTests'])
-        self.assertEqual(databases, set())
-        self.assertIn(self.skip_msg + 'default, other', output)
+        self.assertSkippedDatabases([
+            'test_runner_apps.databases.tests.NoDatabaseTests'
+        ], set())
diff --git a/tests/test_utils/test_transactiontestcase.py b/tests/test_utils/test_transactiontestcase.py
index 3a9d173138..4e183a5196 100644
--- a/tests/test_utils/test_transactiontestcase.py
+++ b/tests/test_utils/test_transactiontestcase.py
@@ -44,7 +44,7 @@ class TransactionTestCaseDatabasesTests(TestCase):
         so that it's less likely to overflow. An overflow causes
         assertNumQueries() to fail.
         """
-        for alias in connections:
+        for alias in self.databases:
             self.assertEqual(len(connections[alias].queries_log), 0, 'Failed for alias %s' % alias)