M34: enforce domain integrity in PostgreSQL

backend/tests/test_database_constraints.py

@@ -0,0 +1,23 @@
+import pytest
+from sqlalchemy import text
+from sqlalchemy.exc import IntegrityError
+
+from app.core.db import SessionLocal
+
+
+@pytest.mark.parametrize(
+    ("statement", "constraint_name"),
+    (
+        ("UPDATE vehicles SET odometer_km = -1 WHERE public_ref = 'MO-001'", "ck_vehicles_odometer"),
+        ("UPDATE bookings SET ends_at = starts_at WHERE public_ref = 'BK-DEMO-RETURN'", "ck_bookings_time_window"),
+        ("UPDATE data_quality_issues SET status = 'invented' WHERE public_ref = 'DQ-DEMO-DUPLICATE'", "ck_data_quality_status"),
+        ("UPDATE outbox_events SET attempts = -1", "ck_outbox_attempts"),
+    ),
+)
+def test_database_rejects_invalid_domain_state(statement: str, constraint_name: str) -> None:
+    with SessionLocal() as db:
+        with pytest.raises(IntegrityError) as caught:
+            db.execute(text(statement))
+            db.commit()
+        db.rollback()
+    assert constraint_name in str(caught.value)