Tests: simplify test_settings maintenance

If no version-specific tests.test_settings.settings* file
exists for the current Django version, fall back to an
earlier settings file.

- runtests.py find latest settings_N_M earlier than or
  matching Django version N.M being tested, rather than
  requiring exact match
- remove test_settings files that were just duplicates
  of earlier versions

runtests.py

@@ -5,14 +5,53 @@
 # runtests.py [tests.test_x tests.test_y.SomeTestCase ...]
 
 import os
+import re
 import sys
 import warnings
+from pathlib import Path
 
 import django
 from django.conf import settings
 from django.test.utils import get_runner
 
 
+def find_test_settings():
+    """
+    Return dotted path to Django settings compatible with current Django version.
+
+    Finds highest tests.test_settings.settings_N_M.py where N.M is <= Django version.
+    (Generally, default Django settings don't change meaningfully between Django
+    releases, so this will fall back to the most recent settings when there isn't an
+    exact match for the current version, while allowing creation of new settings
+    files to test significant differences.)
+    """
+    django_version = django.VERSION[:2]  # (major, minor)
+    found_version = None  # (major, minor)
+    found_path = None
+
+    for settings_path in Path("tests/test_settings").glob("settings_*.py"):
+        try:
+            (major, minor) = re.match(
+                r"settings_(\d+)_(\d+)\.py", settings_path.name
+            ).groups()
+            settings_version = (int(major), int(minor))
+        except (AttributeError, TypeError, ValueError):
+            raise ValueError(
+                f"File '{settings_path!s}' doesn't match settings_N_M.py"
+            ) from None
+        if settings_version <= django_version:
+            if found_version is None or settings_version > found_version:
+                found_version = settings_version
+                found_path = settings_path
+
+    if found_path is None:
+        raise ValueError(f"No suitable test_settings for Django {django.__version__}")
+
+    # Convert Path("test/test_settings/settings_N_M.py")
+    # to dotted module "test.test_settings.settings_N_M":
+    return ".".join(found_path.with_suffix("").parts)
+
+
 def setup_and_run_tests(test_labels=None):
     """Discover and run project tests. Returns number of failures."""
     test_labels = test_labels or ["tests"]
@@ -32,9 +71,9 @@ def setup_and_run_tests(test_labels=None):
     # show DeprecationWarning and other default-ignored warnings:
     warnings.simplefilter("default")
 
-    os.environ["DJANGO_SETTINGS_MODULE"] = (
+    settings_module = find_test_settings()
-        "tests.test_settings.settings_%d_%d" % django.VERSION[:2]
+    print(f"Using settings module {settings_module!r}.")
-    )
+    os.environ["DJANGO_SETTINGS_MODULE"] = settings_module
     django.setup()
 
     TestRunner = get_runner(settings)

tests/test_settings/settings_3_2.py

@@ -1,121 +0,0 @@
-"""
-Django settings for Anymail tests.
-
-Generated by 'django-admin startproject' using Django 3.1.
-
-For more information on this file, see
-https://docs.djangoproject.com/en/dev/topics/settings/
-
-For the full list of settings and their values, see
-https://docs.djangoproject.com/en/dev/ref/settings/
-"""
-
-import os
-
-# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
-BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
-
-
-# Quick-start development settings - unsuitable for production
-# See https://docs.djangoproject.com/en/dev/howto/deployment/checklist/
-
-# SECURITY WARNING: keep the secret key used in production secret!
-SECRET_KEY = 'NOT_FOR_PRODUCTION_USE'
-
-# SECURITY WARNING: don't run with debug turned on in production!
-DEBUG = True
-
-ALLOWED_HOSTS = []
-
-
-# Application definition
-
-INSTALLED_APPS = [
-    'django.contrib.admin',
-    'django.contrib.auth',
-    'django.contrib.contenttypes',
-    'django.contrib.sessions',
-    'django.contrib.messages',
-    'django.contrib.staticfiles',
-    'anymail',
-]
-
-MIDDLEWARE = [
-    'django.middleware.security.SecurityMiddleware',
-    'django.contrib.sessions.middleware.SessionMiddleware',
-    'django.middleware.common.CommonMiddleware',
-    'django.middleware.csrf.CsrfViewMiddleware',
-    'django.contrib.auth.middleware.AuthenticationMiddleware',
-    'django.contrib.messages.middleware.MessageMiddleware',
-    'django.middleware.clickjacking.XFrameOptionsMiddleware',
-]
-
-ROOT_URLCONF = 'tests.test_settings.urls'
-
-TEMPLATES = [
-    {
-        'BACKEND': 'django.template.backends.django.DjangoTemplates',
-        'DIRS': [],
-        'APP_DIRS': True,
-        'OPTIONS': {
-            'context_processors': [
-                'django.template.context_processors.debug',
-                'django.template.context_processors.request',
-                'django.contrib.auth.context_processors.auth',
-                'django.contrib.messages.context_processors.messages',
-            ],
-        },
-    },
-]
-
-WSGI_APPLICATION = 'tests.wsgi.application'
-
-
-# Database
-# https://docs.djangoproject.com/en/dev/ref/settings/#databases
-
-DATABASES = {
-    'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
-    }
-}
-
-
-# Password validation
-# https://docs.djangoproject.com/en/dev/ref/settings/#auth-password-validators
-
-AUTH_PASSWORD_VALIDATORS = [
-    {
-        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
-    },
-]
-
-
-# Internationalization
-# https://docs.djangoproject.com/en/dev/topics/i18n/
-
-LANGUAGE_CODE = 'en-us'
-
-TIME_ZONE = 'UTC'
-
-USE_I18N = True
-
-USE_L10N = True
-
-USE_TZ = True
-
-
-# Static files (CSS, JavaScript, Images)
-# https://docs.djangoproject.com/en/dev/howto/static-files/
-
-STATIC_URL = '/static/'

tests/test_settings/settings_4_1.py

@@ -1,124 +0,0 @@
-"""
-Django settings for Anymail tests.
-
-Generated by 'django-admin startproject' using Django 4.0.1.
-
-For more information on this file, see
-https://docs.djangoproject.com/en/4.0/topics/settings/
-
-For the full list of settings and their values, see
-https://docs.djangoproject.com/en/4.0/ref/settings/
-"""
-
-from pathlib import Path
-
-# Build paths inside the project like this: BASE_DIR / 'subdir'.
-BASE_DIR = Path(__file__).resolve().parent.parent
-
-
-# Quick-start development settings - unsuitable for production
-# See https://docs.djangoproject.com/en/4.0/howto/deployment/checklist/
-
-# SECURITY WARNING: keep the secret key used in production secret!
-SECRET_KEY = 'NOT_FOR_PRODUCTION_USE'
-
-# SECURITY WARNING: don't run with debug turned on in production!
-DEBUG = True
-
-ALLOWED_HOSTS = []
-
-
-# Application definition
-
-INSTALLED_APPS = [
-    'django.contrib.admin',
-    'django.contrib.auth',
-    'django.contrib.contenttypes',
-    'django.contrib.sessions',
-    'django.contrib.messages',
-    'django.contrib.staticfiles',
-    'anymail',
-]
-
-MIDDLEWARE = [
-    'django.middleware.security.SecurityMiddleware',
-    'django.contrib.sessions.middleware.SessionMiddleware',
-    'django.middleware.common.CommonMiddleware',
-    'django.middleware.csrf.CsrfViewMiddleware',
-    'django.contrib.auth.middleware.AuthenticationMiddleware',
-    'django.contrib.messages.middleware.MessageMiddleware',
-    'django.middleware.clickjacking.XFrameOptionsMiddleware',
-]
-
-ROOT_URLCONF = 'tests.test_settings.urls'
-
-TEMPLATES = [
-    {
-        'BACKEND': 'django.template.backends.django.DjangoTemplates',
-        'DIRS': [],
-        'APP_DIRS': True,
-        'OPTIONS': {
-            'context_processors': [
-                'django.template.context_processors.debug',
-                'django.template.context_processors.request',
-                'django.contrib.auth.context_processors.auth',
-                'django.contrib.messages.context_processors.messages',
-            ],
-        },
-    },
-]
-
-WSGI_APPLICATION = 'tests.wsgi.application'
-
-
-# Database
-# https://docs.djangoproject.com/en/4.0/ref/settings/#databases
-
-DATABASES = {
-    'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': BASE_DIR / 'db.sqlite3',
-    }
-}
-
-
-# Password validation
-# https://docs.djangoproject.com/en/4.0/ref/settings/#auth-password-validators
-
-AUTH_PASSWORD_VALIDATORS = [
-    {
-        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
-    },
-]
-
-
-# Internationalization
-# https://docs.djangoproject.com/en/4.0/topics/i18n/
-
-LANGUAGE_CODE = 'en-us'
-
-TIME_ZONE = 'UTC'
-
-USE_I18N = True
-
-USE_TZ = True
-
-
-# Static files (CSS, JavaScript, Images)
-# https://docs.djangoproject.com/en/4.0/howto/static-files/
-
-STATIC_URL = 'static/'
-
-# Default primary key field type
-# https://docs.djangoproject.com/en/4.0/ref/settings/#default-auto-field
-
-DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'

tests/test_settings/settings_4_2.py

@@ -1,124 +0,0 @@
-"""
-Django settings for Anymail tests.
-
-Generated by 'django-admin startproject' using Django 4.0.1.
-
-For more information on this file, see
-https://docs.djangoproject.com/en/4.0/topics/settings/
-
-For the full list of settings and their values, see
-https://docs.djangoproject.com/en/4.0/ref/settings/
-"""
-
-from pathlib import Path
-
-# Build paths inside the project like this: BASE_DIR / 'subdir'.
-BASE_DIR = Path(__file__).resolve().parent.parent
-
-
-# Quick-start development settings - unsuitable for production
-# See https://docs.djangoproject.com/en/4.0/howto/deployment/checklist/
-
-# SECURITY WARNING: keep the secret key used in production secret!
-SECRET_KEY = 'NOT_FOR_PRODUCTION_USE'
-
-# SECURITY WARNING: don't run with debug turned on in production!
-DEBUG = True
-
-ALLOWED_HOSTS = []
-
-
-# Application definition
-
-INSTALLED_APPS = [
-    'django.contrib.admin',
-    'django.contrib.auth',
-    'django.contrib.contenttypes',
-    'django.contrib.sessions',
-    'django.contrib.messages',
-    'django.contrib.staticfiles',
-    'anymail',
-]
-
-MIDDLEWARE = [
-    'django.middleware.security.SecurityMiddleware',
-    'django.contrib.sessions.middleware.SessionMiddleware',
-    'django.middleware.common.CommonMiddleware',
-    'django.middleware.csrf.CsrfViewMiddleware',
-    'django.contrib.auth.middleware.AuthenticationMiddleware',
-    'django.contrib.messages.middleware.MessageMiddleware',
-    'django.middleware.clickjacking.XFrameOptionsMiddleware',
-]
-
-ROOT_URLCONF = 'tests.test_settings.urls'
-
-TEMPLATES = [
-    {
-        'BACKEND': 'django.template.backends.django.DjangoTemplates',
-        'DIRS': [],
-        'APP_DIRS': True,
-        'OPTIONS': {
-            'context_processors': [
-                'django.template.context_processors.debug',
-                'django.template.context_processors.request',
-                'django.contrib.auth.context_processors.auth',
-                'django.contrib.messages.context_processors.messages',
-            ],
-        },
-    },
-]
-
-WSGI_APPLICATION = 'tests.wsgi.application'
-
-
-# Database
-# https://docs.djangoproject.com/en/4.0/ref/settings/#databases
-
-DATABASES = {
-    'default': {
-        'ENGINE': 'django.db.backends.sqlite3',
-        'NAME': BASE_DIR / 'db.sqlite3',
-    }
-}
-
-
-# Password validation
-# https://docs.djangoproject.com/en/4.0/ref/settings/#auth-password-validators
-
-AUTH_PASSWORD_VALIDATORS = [
-    {
-        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
-    },
-    {
-        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
-    },
-]
-
-
-# Internationalization
-# https://docs.djangoproject.com/en/4.0/topics/i18n/
-
-LANGUAGE_CODE = 'en-us'
-
-TIME_ZONE = 'UTC'
-
-USE_I18N = True
-
-USE_TZ = True
-
-
-# Static files (CSS, JavaScript, Images)
-# https://docs.djangoproject.com/en/4.0/howto/static-files/
-
-STATIC_URL = 'static/'
-
-# Default primary key field type
-# https://docs.djangoproject.com/en/4.0/ref/settings/#default-auto-field
-
-DEFAULT_AUTO_FIELD = 'django.db.models.BigAutoField'