The parallel test runner uses multiple workers to distribute the
workload. These workers are assigned a worker ID using a globally
incremented variable, which determines what test database to connect
to. When the worker ID surpasses the test database IDs Django will
crash.
This reduce likelihood of crashing parallel tests because
ParallelTestSuite will no longer create more workers than TestCases.
It won't eliminate the problem completely though because there are
other circumstances in which new workers can be created which can then
be assigned an "illegal" worker ID.
Failures detected when loading tests are ordered before all of the
above for quicker feedback. This includes things like test modules that
couldn't be found or that couldn't be loaded due to syntax errors.
This also makes partition_suite_by_type(), partition_suite_by_case(),
filter_tests_by_tags(), and DiscoverRunner._get_databases() to use
iter_test_cases().
Whether or not the state of a test database should be serialized can be
inferred from the set of databases allowed to be access from discovered
TestCase/TransactionTestCase enabling the serialized_rollback feature
which makes this setting unnecessary.
This should make a significant test suite bootstraping time difference
on large projects that didn't explicitly disable test database
serialization.
This fixes flushing test databases when two aliases point to the same
database.
Use a list() to store the test database aliases so the order remains
stable by following the order of the connections. Also, always use the
"default" database alias as the first alias to accommodate `migrate`.
Previously `migrate` could be executed on a secondary alias which
caused truncating the "default" database.
- 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.
Use tempfile.TemporaryDirectory() in AdminScriptTestCase.setUp()
to create and destroy a temporary directory for each test. It removes
the need for individual tests to delete files.
For test classes that don't use the temporary directory, inherit from
SimpleTestCase.
The test was expecting connections used by DiscoverRunner.setup_databases()
to be the ones defined in django.test.runner but this doesn't hold true
since this method was made a proxy of django.test.utils.setup_databases.
This broke the TransactionTestCase.serialized_rollback feature in the test
suite because calls to create_db_test() cleared the test data persisted on
connections objects.
Added an assertions to prevent this from happening again.
Prior to this change foreign key constraint references could be left pointing
at tables dropped during operations simulating unsupported table alterations
because of an unexpected failure to disable foreign key constraint checks.
SQLite3 does not allow disabling such checks while in a transaction so they
must be disabled beforehand.
Thanks ezaquarii for the report and Carlton and Tim for the review.
Data loaded in migrations were restored at the beginning of each
TransactionTestCase and all the tables are truncated at the end of
these test cases. If there was a TransactionTestCase at the end of
the test suite, the migrated data weren't restored in the database
(especially unexpected when using --keepdb). Now data is restored
at the end of each TransactionTestCase.
