Harden location db startup validation

tests/conftest.py

@@ -1,12 +1,51 @@
+from pathlib import Path
+
 import pytest
+from alembic import command
+from alembic.config import Config
 from fastapi.testclient import TestClient
 
+from app.config import get_settings
 from app.main import create_app
 
 
+def _make_alembic_config(database_url: str) -> Config:
+    config = Config("alembic.ini")
+    config.set_main_option("sqlalchemy.url", database_url)
+    return config
+
+
 @pytest.fixture
-def app():
-    return create_app()
+def test_database_urls(tmp_path: Path, monkeypatch: pytest.MonkeyPatch):
+    location_database_path = tmp_path / "location_test.db"
+    poo_database_path = tmp_path / "poo_placeholder.db"
+    location_database_url = f"sqlite:///{location_database_path}"
+    poo_database_url = f"sqlite:///{poo_database_path}"
+
+    monkeypatch.setenv("LOCATION_DATABASE_URL", location_database_url)
+    monkeypatch.setenv("POO_DATABASE_URL", poo_database_url)
+    get_settings.cache_clear()
+
+    try:
+        yield {
+            "location_path": location_database_path,
+            "location_url": location_database_url,
+            "poo_path": poo_database_path,
+            "poo_url": poo_database_url,
+        }
+    finally:
+        get_settings.cache_clear()
+
+
+@pytest.fixture
+def ready_location_database(test_database_urls):
+    command.upgrade(_make_alembic_config(test_database_urls["location_url"]), "head")
+    return test_database_urls
+
+
+@pytest.fixture
+def app(ready_location_database):
+    yield create_app()
 
 
 @pytest.fixture