July 3rd - Review and optimize codes

tests/test_tenant_routing.py

@@ -0,0 +1,40 @@
+"""
+Tests for the tenant routing layer (app/tenancy/routing.py).
+
+The crown-jewel invariant of the multi-tenant design is data isolation: a
+request bound to tenant A must never touch tenant B's database. Full isolation
+proof requires two live tenant DBs and belongs in an integration suite (see
+tests/README.md). What we CAN verify cheaply and deterministically here is the
+other half of the contract:
+
+    "The routing layer is completely inert until a tenant is resolved."
+
+If routing were NOT inert when MULTI_TENANT_ENABLED=false, the existing
+single-tenant deployment would break. This test locks that guarantee in.
+"""
+
+from flask import g
+
+
+def test_routing_is_inert_without_a_resolved_tenant(app):
+    """With no g.tenant_engine set, db.session binds to the default engine."""
+    from app import db
+    with app.test_request_context('/'):
+        # Multi-tenancy disabled → the resolver never sets g.tenant_engine.
+        assert g.get('tenant_engine') is None
+        # …so get_bind() must fall through to the app's default engine.
+        assert db.session.get_bind() is db.engine
+
+
+def test_resolved_tenant_engine_wins(app, monkeypatch):
+    """When g.tenant_engine IS set, get_bind() returns it, not the default."""
+    from app import db
+
+    class _SentinelEngine:
+        """Stand-in object; get_bind should return it verbatim when present."""
+
+    sentinel = _SentinelEngine()
+
+    with app.test_request_context('/'):
+        g.tenant_engine = sentinel
+        assert db.session.get_bind() is sentinel