add markers/tags for migration tests

README.md

@@ -221,6 +221,34 @@ class TestDirectMigration(MigratorTestCase):
         assert SomeItem.objects.filter(is_clean=True).count() == 1
 ```
 
+### Choosing only migrations tests
+
+In CI systems it is important to get instant feedback. Running tests that
+apply database migration can slow down tests execution, so it is often a good
+idea to run standard, fast, regular unit tests without migrations in parallel
+with slower migrations tests.
+
+#### pytest
+
+`django_test_migrations` adds `migration_test` marker to each test using
+`migrator_factory` or `migrator` fixture.
+To run only migrations test, use `-m` option:
+
+```bash
+pytest -m migration_test
+```
+
+#### unittest
+
+`django_test_migrations` adds `migration_test`
+[tag](https://docs.djangoproject.com/en/3.0/topics/testing/tools/#tagging-tests)
+to every `MigratorTestCase` subclass.
+To run only migrations tests, use `--tag` option:
+
+```bash
+python mange.py test --tag=migration_test
+```
+
 
 ## Django Checks
 

django_test_migrations/constants.py

@@ -0,0 +1,4 @@
+from typing_extensions import Final
+
+#: marker/tag indicating that marked test is Django's migrations test
+MIGRATION_TEST_MARKER: Final = 'migration_test'

django_test_migrations/contrib/pytest_plugin.py

@@ -4,6 +4,30 @@
 from django.db import DEFAULT_DB_ALIAS
 from django.db.models.signals import post_migrate, pre_migrate
 
+from django_test_migrations.constants import MIGRATION_TEST_MARKER
+
+
+def pytest_load_initial_conftests(early_config):
+    """Register pytest's markers."""
+    early_config.addinivalue_line(
+        'markers',
+        "{0}: mark the test as a Django's migration test.".format(
+            MIGRATION_TEST_MARKER,
+        ),
+    )
+
+
+def pytest_collection_modifyitems(session, items):  # noqa: WPS110
+    """Mark all tests using ``migrator_factory`` fixture with proper marks.
+
+    Add ``MIGRATION_TEST_MARKER`` marker to all items using
+    ``migrator_factory`` fixture.
+
+    """
+    for pytest_item in items:
+        if 'migrator_factory' in getattr(pytest_item, 'fixturenames', []):
+            pytest_item.add_marker(MIGRATION_TEST_MARKER)
+
 
 @pytest.fixture()
 def migrator_factory(request, transactional_db, django_db_use_migrations):

django_test_migrations/contrib/unittest_case.py

@@ -2,12 +2,14 @@
 
 from django.db.migrations.state import ProjectState
 from django.db.models.signals import post_migrate, pre_migrate
-from django.test import TransactionTestCase
+from django.test import TransactionTestCase, tag
 
+from django_test_migrations.constants import MIGRATION_TEST_MARKER
 from django_test_migrations.migrator import Migrator
 from django_test_migrations.types import MigrationSpec
 
 
+@tag(MIGRATION_TEST_MARKER)
 class MigratorTestCase(TransactionTestCase):
     """Used when using raw ``unitest`` library for test."""
 

setup.cfg

@@ -98,6 +98,7 @@ branch = True
 # And we completely test it anyway.
 omit =
   django_test_migrations/contrib/pytest_plugin.py
+  django_test_migrations/constants.py
 
 [coverage:report]
 skip_covered = True

tests/test_contrib/test_pytest_plugin/test_plugin.py

@@ -1,5 +1,8 @@
+import re
 import subprocess
 
+from django_test_migrations.constants import MIGRATION_TEST_MARKER
+
 
 def test_call_pytest_setup_plan():
     """Checks that module is registered and visible in the meta data."""
@@ -19,3 +22,44 @@ def test_call_pytest_setup_plan():
 
     assert 'migrator' in output_text
     assert 'migrator_factory' in output_text
+
+
+def test_pytest_registers_marker():
+    """Ensure ``MIGRATION_TEST_MARKER`` marker is registered."""
+    output_text = subprocess.check_output(
+        ['pytest', '--markers'],
+        stderr=subprocess.STDOUT,
+        universal_newlines=True,
+        encoding='utf8',
+    )
+
+    assert MIGRATION_TEST_MARKER in output_text
+
+
+def test_pytest_markers():
+    """Ensure ``MIGRATION_TEST_MARKER`` markers are properly added."""
+    output_text = subprocess.check_output(
+        [
+            'pytest',
+            '--collect-only',
+
+            # Collect only tests marked with ``MIGRATION_TEST_MARKER`` marker
+            '-m',
+            MIGRATION_TEST_MARKER,
+
+            # We need this part because otherwise check fails with `1` code:
+            '--cov-fail-under',
+            '0',
+        ],
+        stderr=subprocess.STDOUT,
+        universal_newlines=True,
+        encoding='utf8',
+    )
+
+    search_result = re.search(
+        r'(?P<selected_number>\d+)\s+selected',
+        output_text,
+    )
+    assert search_result
+    assert int(search_result.group('selected_number') or 0) > 0
+    assert 'test_pytest_plugin' in output_text

tests/test_contrib/test_unittest_case/test_unittest_case.py

@@ -1,3 +1,4 @@
+from django_test_migrations.constants import MIGRATION_TEST_MARKER
 from django_test_migrations.contrib.unittest_case import MigratorTestCase
 
 
@@ -38,3 +39,9 @@ def test_migration_main0001(self):
         SomeItem = self.new_state.apps.get_model('main_app', 'SomeItem')
 
         assert SomeItem.objects.count() == 2
+
+
+def test_migration_test_marker_tag():
+    """Ensure ``MigratorTestCase`` sublasses are properly tagged."""
+    assert MIGRATION_TEST_MARKER in TestDirectMigration.tags
+    assert MIGRATION_TEST_MARKER in TestBackwardMigration.tags