Flask 2.2 test_client crashes on Werkzeug 3: werkzeug.__version__ missing

With Flask 2.2.x installed alongside Werkzeug 3.x, app.test_client() raises AttributeError: module 'werkzeug' has no attribute '__version__' (flask/testing.py builds the User-Agent from it, and Werkzeug 3 removed it). The app code is fine; it's an environment version mismatch. Fix properly by upgrading Flask to >=3 or pinning werkzeug<3. To smoke-test a route without touching the env, call the view inside with app.test_request_context('/path'): and inspect the returned Response (.status_code, .json, .headers).