dixi, AFAIR the Trident accident was during a pre-delivery production test flight, thus additional experimental test-flight devices were not fitted.
Nowadays where pre-delivery testing requires a stall check either with or without stick push (stall ident) enabled, an additional glare-shield stall panel is fitted showing AoA calibrated for stick shake / push. Preflight the AoA vanes and indicator are crosschecked, so that if when inflight the shake / push do not occur at the expected AOA then the test is stopped.
The BAe 146 used such a panel, which may also have been approved for training stalls, providing the shake / push was enabled and checked / calibrated preflight.