[DB] adopt the AdHocDbFixture from oslo

I0163e637ffef6d45d2573ebe29b5438911d01fce added a new way of doing
testing with oslo db by providing resuable test fixtures.
watcher like many project hand roled there own before that was intoduced.

This change simply removes our custom fixutres and adopts the standard
fixture form oslo.db

Generated-By: cursor gpt-5.1
Change-Id: I9519fd521ea06a5198eddf021b655e8557e7ef51
Signed-off-by: Sean Mooney <work@seanmooney.info>

watcher/tests/db/base.py

@@ -15,7 +15,6 @@
 
 """Watcher DB test base class."""
 
-import fixtures
 from oslo_config import cfg
 from oslo_db.sqlalchemy import enginefacade
 from oslo_db.sqlalchemy import test_fixtures
@@ -23,7 +22,6 @@ from oslo_db.sqlalchemy import test_fixtures
 
 from watcher.db import api as dbapi
 from watcher.db.sqlalchemy import migration
-from watcher.db.sqlalchemy import models
 from watcher.tests import base
 from watcher.tests.db import utils
 
@@ -32,37 +30,24 @@ CONF = cfg.CONF
 
 CONF.import_opt('enable_authentication', 'watcher.api.acl')
 
-_DB_CACHE = None
 
+class SqliteDatabaseFixture(test_fixtures.GeneratesSchema,
+                            test_fixtures.AdHocDbFixture):
+    """oslo_db-based fixture for SQLite-backed tests.
 
-class Database(fixtures.Fixture):
+    This uses oslo_db's AdHocDbFixture to provision a per-test (or per-run)
+    SQLite database and GenerateSchema to build the Watcher schema via the
+    normal migration helpers.
+    """
 
-    def __init__(self, engine, db_migrate, sql_connection):
-        self.sql_connection = sql_connection
+    def __init__(self):
+        # Use the configured database connection URL
+        # (set to sqlite:// in tests)
+        super().__init__(url=CONF.database.connection)
 
-        self.engine = engine
-        self.engine.dispose()
-
-        with self.engine.connect() as conn:
-            self.setup_sqlite(db_migrate)
-            self.post_migrations()
-            self._DB = "".join(line for line in conn.connection.iterdump())
-        self.engine.dispose()
-
-    def setup_sqlite(self, db_migrate):
-        if db_migrate.version():
-            return
-        models.Base.metadata.create_all(self.engine)
-        db_migrate.stamp('head')
-
-    def setUp(self):
-        super().setUp()
-        with self.engine.connect() as conn:
-            conn.connection.executescript(self._DB)
-        self.addCleanup(self.engine.dispose)
-
-    def post_migrations(self):
-        """Any addition steps that are needed outside of the migrations."""
+    def generate_schema_create_all(self, engine):
+        """Generate the database schema for tests using migrations helpers."""
+        migration.create_schema(engine=engine)
 
 
 class DbTestCase(base.TestCase):
@@ -77,15 +62,10 @@ class DbTestCase(base.TestCase):
 
         super().setUp()
 
+        # Provision and configure a SQLite database for this test using
+        # oslo_db's fixtures.
+        self.useFixture(SqliteDatabaseFixture())
         self.dbapi = dbapi.get_instance()
-
-        global _DB_CACHE
-        if not _DB_CACHE:
-            engine = enginefacade.writer.get_engine()
-            _DB_CACHE = Database(engine, migration,
-                                 sql_connection=CONF.database.connection)
-            engine.dispose()
-        self.useFixture(_DB_CACHE)
         self._id_gen = utils.id_generator()