test: use PostgreSQL and live model integrations

backend/tests/conftest.py

@@ -1,13 +1,28 @@
 import os
 from pathlib import Path
+from uuid import uuid4
 
 import pytest
+from alembic import command
+from alembic.config import Config
+from sqlalchemy import create_engine
+from sqlalchemy.engine import make_url
 from sqlalchemy.orm import sessionmaker
 
 from wisegrade.config import get_settings
-from wisegrade.db import Base, engine_for
+from wisegrade.db import engine_for
 from wisegrade.seed import seed_initial
-from wisegrade import models  # noqa: F401
+
+
+@pytest.fixture(scope="session")
+def test_database_url():
+    value = os.environ.get("TEST_DATABASE_URL")
+    if not value:
+        pytest.fail("Set TEST_DATABASE_URL to a dedicated PostgreSQL database named wisegrade_tests")
+    url = make_url(value)
+    if url.drivername != "postgresql+psycopg" or url.database != "wisegrade_tests":
+        pytest.fail("TEST_DATABASE_URL must use postgresql+psycopg and the wisegrade_tests database")
+    return url
 
 
 @pytest.fixture
@@ -24,14 +39,35 @@ def environment(tmp_path, monkeypatch):
 
 
 @pytest.fixture
-def session_factory(environment):
-    engine = engine_for(f"sqlite:///{environment / 'test.db'}")
-    Base.metadata.create_all(engine)
-    factory = sessionmaker(bind=engine, expire_on_commit=False)
-    with factory() as db:
-        seed_initial(db)
-    yield factory
-    engine.dispose()
+def session_factory(environment, monkeypatch, test_database_url):
+    admin_engine = create_engine(test_database_url, isolation_level="AUTOCOMMIT")
+    name = f"wisegrade_test_{uuid4().hex}"
+    engine = None
+    created = False
+    try:
+        with admin_engine.connect() as connection:
+            connection.exec_driver_sql(f'CREATE DATABASE "{name}"')
+        created = True
+        url = test_database_url.set(database=name).render_as_string(hide_password=False)
+        monkeypatch.setenv("DATABASE_URL", url)
+        get_settings.cache_clear()
+        backend_root = Path(__file__).resolve().parents[1]
+        migration_config = Config(str(backend_root / "alembic.ini"))
+        migration_config.set_main_option("script_location", str(backend_root / "migrations"))
+        command.upgrade(migration_config, "head")
+        engine = engine_for(url)
+        factory = sessionmaker(bind=engine, expire_on_commit=False)
+        with factory() as db:
+            seed_initial(db)
+        yield factory
+    finally:
+        if engine is not None:
+            engine.dispose()
+        get_settings.cache_clear()
+        if created:
+            with admin_engine.connect() as connection:
+                connection.exec_driver_sql(f'DROP DATABASE "{name}" WITH (FORCE)')
+        admin_engine.dispose()
 
 
 @pytest.fixture