M39: harden application and acceptance gates

backend/tests/test_migrations.py

@@ -0,0 +1,88 @@
+"""Guard against model/migration drift.
+
+The functional suite builds its schema with ``Base.metadata.create_all`` for speed, so a
+column or index added to a model but never written into an Alembic migration would only
+surface on the first real deployment. This test runs the migration chain from an empty
+database and asserts that Alembic's autogenerate sees nothing left to do.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import pytest
+from alembic.autogenerate import compare_metadata
+from alembic.config import Config
+from alembic.runtime.migration import MigrationContext
+from sqlalchemy import create_engine, text
+from sqlalchemy.engine import make_url
+
+from alembic import command
+from app.core.config import get_settings
+from app.models import Base
+
+BACKEND_DIR = Path(__file__).resolve().parents[1]
+SCRATCH_DB = "mobilityops_migration_check"
+
+
+@pytest.fixture(scope="module")
+def migrated_database_url() -> str:
+    settings = get_settings()
+    base_url = make_url(settings.database_url)
+    admin_engine = create_engine(
+        base_url.set(database="postgres"), isolation_level="AUTOCOMMIT", poolclass=None
+    )
+    with admin_engine.connect() as conn:
+        conn.execute(text(f'DROP DATABASE IF EXISTS "{SCRATCH_DB}"'))
+        conn.execute(text(f'CREATE DATABASE "{SCRATCH_DB}"'))
+    scratch_url = base_url.set(database=SCRATCH_DB).render_as_string(hide_password=False)
+    try:
+        yield scratch_url
+    finally:
+        admin_engine.dispose()
+        admin_engine = create_engine(
+            base_url.set(database="postgres"), isolation_level="AUTOCOMMIT", poolclass=None
+        )
+        with admin_engine.connect() as conn:
+            conn.execute(text(f'DROP DATABASE IF EXISTS "{SCRATCH_DB}" WITH (FORCE)'))
+        admin_engine.dispose()
+
+
+def _alembic_config(database_url: str) -> Config:
+    config = Config(str(BACKEND_DIR / "alembic.ini"))
+    config.set_main_option("script_location", str(BACKEND_DIR / "alembic"))
+    config.set_main_option("sqlalchemy.url", database_url)
+    return config
+
+
+def test_migrations_upgrade_from_empty_and_match_models(migrated_database_url: str) -> None:
+    config = _alembic_config(migrated_database_url)
+    # env.py reads DATABASE_URL from settings; override it for the scratch database.
+    import os
+
+    previous = os.environ.get("DATABASE_URL")
+    os.environ["DATABASE_URL"] = migrated_database_url
+    get_settings.cache_clear()
+    try:
+        command.upgrade(config, "head")
+    finally:
+        if previous is None:
+            os.environ.pop("DATABASE_URL", None)
+        else:
+            os.environ["DATABASE_URL"] = previous
+        get_settings.cache_clear()
+
+    engine = create_engine(migrated_database_url)
+    try:
+        with engine.connect() as conn:
+            context = MigrationContext.configure(
+                conn, opts={"compare_type": True, "compare_server_default": False}
+            )
+            diff = compare_metadata(context, Base.metadata)
+    finally:
+        engine.dispose()
+
+    assert diff == [], (
+        "Models and Alembic migrations have drifted; write a migration for:\n"
+        + "\n".join(repr(entry) for entry in diff)
+    )