Run test database through Docker (#1198)

This PR makes pytest control Docker, rather than rely on it being
manually started. This makes it easier to run tests from scratch,
guarantees separate database servers for parallel test runs, and allows
us to vary the database more easily too.

Author: adamchainz

.github/workflows/main.yml

@@ -34,19 +34,8 @@ jobs:
         - mariadb:11.4
         - mariadb:10.11
 
-    services:
-      database:
-        image: ${{ matrix.database }}
-        env:
-          MYSQL_ROOT_PASSWORD: hunter2
-        ports:
-        - 3306:3306
-        options: --tmpfs /var/lib/mysql
-
     env:
-      DB_HOST: 127.0.0.1
-      DB_USER: root
-      DB_PASSWORD: hunter2
+      DB_IMAGE: ${{ matrix.database }}
 
     steps:
     - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2

CONTRIBUTING.rst

@@ -5,35 +5,27 @@ Contributing
 Run the tests
 -------------
 
-1. Install `tox <https://tox.wiki/en/latest/>`__.
+1. Install `tox <https://tox.wiki/en/latest/>`__ and ensure Docker is running.
 
-2. Run a supported version of MySQL or MariaDB.
-   This is easiest with the official Docker images.
-   For example:
+2. Run the tests:
 
    .. code-block:: console
 
-      docker run --detach --name mariadb -e MYSQL_ROOT_PASSWORD=hunter2 --publish 3306:3306 mariadb:11.6
+      tox -e py314-django61
 
-3. Run the tests by passing environment variables with your connection parameters.
-   For the above Docker command:
+   By default this uses the ``mariadb:11.4`` image.
+   To use a different image, set ``DB_IMAGE``:
 
    .. code-block:: console
 
-      DB_HOST=127.0.0.1 DB_USER=root DB_PASSWORD='hunter2' tox -e py313-django52
+      DB_IMAGE=mysql:8.4 tox -e py314-django61
 
-  tox environments are split per Python and Django version.
+   tox environments are split per Python and Django version.
 
-  You can run a subset of tests by passing them after ``--`` like:
-
-  .. code-block:: console
-
-    DB_HOST=127.0.0.1 DB_USER=root DB_PASSWORD='hunter2' tox -e py313-django51 -- tests/testapp/test_cache.py
-
-  You can also pass other pytest arguments after the ``--``.
-
-4. When you’re done, shut down the Docker container with:
+   You can run a subset of tests by passing them after ``--`` like:
 
    .. code-block:: console
 
-      docker rm --force mariadb
+      tox -e py314-django61 -- tests/testapp/test_cache.py
+
+   You can also pass other pytest arguments after the ``--``.

tests/conftest.py

@@ -1,23 +1,77 @@
 from __future__ import annotations
 
+import os
+import subprocess
+import time
 import warnings
 
-import django
-from django.db import connection
-from pytest_django.plugin import blocking_manager_key
+import MySQLdb
+import pytest
+from django.conf import settings
 
 
-def pytest_report_header(config):
-    dot_version = ".".join(str(x) for x in django.VERSION)
-    header = "Django version: " + dot_version
+@pytest.fixture(scope="session", autouse=True)
+def mysql_server():
+    image = os.environ.get("DB_IMAGE", "mariadb:11.4")
+    name = f"django-mysql-test-{os.getpid()}"
 
-    pytest_django_db_blocker = config.stash[blocking_manager_key]
-    with pytest_django_db_blocker.unblock(), connection._nodb_cursor() as cursor:
-        cursor.execute("SELECT VERSION()")
-        version = cursor.fetchone()[0]
-        header += f"\nMySQL version: {version}"
+    subprocess.run(
+        [
+            "docker",
+            "run",
+            "--detach",
+            "--name",
+            name,
+            "-e",
+            "MYSQL_ROOT_PASSWORD=hunter2",
+            "--publish",
+            "127.0.0.1::3306",
+            image,
+        ],
+        check=True,
+    )
 
-    return header
+    try:
+        port = (
+            subprocess.check_output(
+                [
+                    "docker",
+                    "inspect",
+                    name,
+                    "--format",
+                    '{{(index (index .NetworkSettings.Ports "3306/tcp") 0).HostPort}}',
+                ]
+            )
+            .decode()
+            .strip()
+        )
+
+        for db in settings.DATABASES.values():
+            if db["ENGINE"] != "django.db.backends.sqlite3":
+                db["HOST"] = "127.0.0.1"
+                db["PORT"] = port
+                db["USER"] = "root"
+                db["PASSWORD"] = "hunter2"
+
+        deadline = time.monotonic() + 60
+        while True:
+            try:
+                conn = MySQLdb.connect(
+                    host="127.0.0.1",
+                    port=int(port),
+                    user="root",
+                    password="hunter2",
+                )
+                conn.close()
+                break
+            except MySQLdb.OperationalError:
+                if time.monotonic() > deadline:  # pragma: no cover
+                    raise RuntimeError("MySQL did not become ready in time")
+                time.sleep(0.5)
+
+        yield
+    finally:
+        subprocess.run(["docker", "rm", "--force", name], check=True)
 
 
 # MySQL 5.7 warns about some sql mode changes

tests/settings.py

@@ -12,20 +12,22 @@
     "default": {
         "ENGINE": "tests.db_backend",
         "NAME": "django_mysql",
-        "USER": os.environ.get("DB_USER", ""),
-        "PASSWORD": os.environ.get("DB_PASSWORD", ""),
-        "HOST": os.environ.get("DB_HOST", ""),
-        "PORT": os.environ.get("DB_PORT", ""),
+        # Filled in by conftest.py
+        "USER": "",
+        "PASSWORD": "",
+        "HOST": "",
+        "PORT": "",
         "OPTIONS": {"charset": "utf8mb4"},
         "TEST": {"COLLATION": "utf8mb4_general_ci", "CHARSET": "utf8mb4"},
     },
     "other": {
         "ENGINE": "tests.db_backend",
         "NAME": "django_mysql2",
-        "USER": os.environ.get("DB_USER", ""),
-        "PASSWORD": os.environ.get("DB_PASSWORD", ""),
-        "HOST": os.environ.get("DB_HOST", ""),
-        "PORT": os.environ.get("DB_PORT", ""),
+        # Filled in by conftest.py
+        "USER": "",
+        "PASSWORD": "",
+        "HOST": "",
+        "PORT": "",
         "OPTIONS": {"charset": "utf8mb4"},
         "TEST": {"COLLATION": "utf8mb4_general_ci", "CHARSET": "utf8mb4"},
     },

tox.ini

@@ -13,10 +13,7 @@ runner = uv-venv-lock-runner
 package = wheel
 wheel_build_env = .pkg
 pass_env =
-    DB_HOST
-    DB_PASSWORD
-    DB_PORT
-    DB_USER
+    DB_IMAGE
 set_env =
     PYTHONDEVMODE = 1
 commands =