Rename test databases when running parallel Tox

When tests are executed using Tox in parallel, modify the test database
names, to avoid name collisions between processes.

This change renames the existing
`django_db_modify_db_settings_xdist_suffix` fixture, to a generic
`django_db_modify_db_settings_parallel_suffix` one, in case more
scenarios/tools have to be considered in the future.

It also handles projects where both `pytest-xdist` and parallel `tox`
are being using, generating database names like
`test_default_py37-django21_gw0`.

Resolves #678.

Author: adamantike

docs/database.rst

@@ -191,21 +191,43 @@ If you need to customize the location of your test database, this is the
 fixture you want to override.
 
 The default implementation of this fixture requests the
-:fixture:`django_db_modify_db_settings_xdist_suffix` to provide compatibility
+:fixture:`django_db_modify_db_settings_parallel_suffix` to provide compatibility
 with pytest-xdist.
 
 This fixture is by default requested from :fixture:`django_db_setup`.
 
+django_db_modify_db_settings_parallel_suffix
+""""""""""""""""""""""""""""""""""""""""""""
+
+.. fixture:: django_db_modify_db_settings_parallel_suffix
+
+Requesting this fixture will add a suffix to the database name when the tests
+are run via `pytest-xdist`, or via `tox` in parallel mode.
+
+This fixture is by default requested from
+:fixture:`django_db_modify_db_settings`.
+
+django_db_modify_db_settings_tox_suffix
+"""""""""""""""""""""""""""""""""""""""
+
+.. fixture:: django_db_modify_db_settings_tox_suffix
+
+Requesting this fixture will add a suffix to the database name when the tests
+are run via `tox` in parallel mode.
+
+This fixture is by default requested from
+:fixture:`django_db_modify_db_settings_parallel_suffix`.
+
 django_db_modify_db_settings_xdist_suffix
 """""""""""""""""""""""""""""""""""""""""
 
 .. fixture:: django_db_modify_db_settings_xdist_suffix
 
 Requesting this fixture will add a suffix to the database name when the tests
-are run via pytest-xdist.
+are run via `pytest-xdist`.
 
 This fixture is by default requested from
-:fixture:`django_db_modify_db_settings`.
+:fixture:`django_db_modify_db_settings_parallel_suffix`.
 
 django_db_use_migrations
 """"""""""""""""""""""""

pytest_django/fixtures.py

@@ -33,35 +33,35 @@
 
 
 @pytest.fixture(scope="session")
-def django_db_modify_db_settings_xdist_suffix(request):
+def django_db_modify_db_settings_tox_suffix(request):
     skip_if_no_django()
 
-    from django.conf import settings
+    tox_environment = os.environ.get("TOX_PARALLEL_ENV")
+    if tox_environment:
+        # Put a suffix like _py27-django21 on tox workers
+        _set_suffix_to_test_databases(suffix=tox_environment)
 
-    for db_settings in settings.DATABASES.values():
-
-        try:
-            test_name = db_settings["TEST"]["NAME"]
-        except KeyError:
-            test_name = None
 
-        if not test_name:
-            if db_settings["ENGINE"] == "django.db.backends.sqlite3":
-                return ":memory:"
-            else:
-                test_name = "test_{}".format(db_settings["NAME"])
+@pytest.fixture(scope="session")
+def django_db_modify_db_settings_xdist_suffix(request):
+    skip_if_no_django()
 
+    xdist_suffix = getattr(request.config, "slaveinput", {}).get("slaveid")
+    if xdist_suffix:
         # Put a suffix like _gw0, _gw1 etc on xdist processes
-        xdist_suffix = getattr(request.config, "slaveinput", {}).get("slaveid")
-        if test_name != ":memory:" and xdist_suffix is not None:
-            test_name = "{}_{}".format(test_name, xdist_suffix)
+        _set_suffix_to_test_databases(suffix=xdist_suffix)
 
-        db_settings.setdefault("TEST", {})
-        db_settings["TEST"]["NAME"] = test_name
+
+@pytest.fixture(scope="session")
+def django_db_modify_db_settings_parallel_suffix(
+    django_db_modify_db_settings_tox_suffix,
+    django_db_modify_db_settings_xdist_suffix,
+):
+    skip_if_no_django()
 
 
 @pytest.fixture(scope="session")
-def django_db_modify_db_settings(django_db_modify_db_settings_xdist_suffix):
+def django_db_modify_db_settings(django_db_modify_db_settings_parallel_suffix):
     skip_if_no_django()
 
 
@@ -153,6 +153,31 @@ def _disable_native_migrations():
     settings.MIGRATION_MODULES = DisableMigrations()
 
 
+def _set_suffix_to_test_databases(suffix):
+    if not suffix:
+        return
+
+    from django.conf import settings
+
+    for db_settings in settings.DATABASES.values():
+
+        try:
+            test_name = db_settings["TEST"]["NAME"]
+        except KeyError:
+            test_name = None
+
+        if not test_name:
+            if db_settings["ENGINE"] == "django.db.backends.sqlite3":
+                continue
+            test_name = "test_{}".format(db_settings["NAME"])
+
+        if test_name == ":memory:":
+            continue
+
+        db_settings.setdefault("TEST", {})
+        db_settings["TEST"]["NAME"] = "{}_{}".format(test_name, suffix)
+
+
 # ############### User visible fixtures ################
 
 

pytest_django/plugin.py

@@ -21,6 +21,8 @@
 from .fixtures import django_db_keepdb  # noqa
 from .fixtures import django_db_createdb  # noqa
 from .fixtures import django_db_modify_db_settings  # noqa
+from .fixtures import django_db_modify_db_settings_parallel_suffix  # noqa
+from .fixtures import django_db_modify_db_settings_tox_suffix  # noqa
 from .fixtures import django_db_modify_db_settings_xdist_suffix  # noqa
 from .fixtures import _live_server_helper  # noqa
 from .fixtures import admin_client  # noqa