Failure Simulation & Diagnostics Validation

#!/usr/bin/env python3
# Test: safe state transition timing after sensor fault injection
# Requirement: [ASIL-D] ECU shall reach safe state within FTTI = 200 ms

import time

class SafeStateTest:
    FTTI_MS = 200   # Fault Tolerance Time Interval
    FHTI_MS = 100   # Fault Handling Time Interval (FTTI / 2)

    def run(self, hil, ecu_monitor):
        results = []

        for fault_type in ["SHORT_GND", "OPEN_CIRCUIT", "STUCK_HIGH"]:
            print(f"Testing safe state for fault: {fault_type}")

            # Establish nominal operating condition
            hil.set("Plant/Speed_kph", 100.0)
            hil.set("Plant/Motor/Torque_Nm", 50.0)
            time.sleep(2)

            # Record pre-fault actuator state
            pre_torque = ecu_monitor.get("ECU/Motor/TorqueCmd_Nm")
            assert abs(pre_torque - 50.0) < 5.0, "Pre-fault state wrong"

            # Inject fault and start timer
            t_fault = time.time()
            hil.inject_fault("TorqueSensor_ChA", fault_type)

            # Poll for safe state (motor torque = 0)
            safe_reached = False
            t_safe = None
            while (time.time() - t_fault) * 1000 < self.FTTI_MS + 50:
                torque = ecu_monitor.get("ECU/Motor/TorqueCmd_Nm")
                if abs(torque) < 1.0:  # safe state = 0 Nm
                    t_safe = (time.time() - t_fault) * 1000
                    safe_reached = True
                    break
                time.sleep(0.005)

            passed = safe_reached and t_safe <= self.FTTI_MS
            print(f"  {fault_type}: safe state at {t_safe:.1f} ms -- {"PASS" if passed else "FAIL"}")
            results.append({"fault": fault_type, "pass": passed,
                            "time_ms": t_safe})

            # Clear fault and recover
            hil.clear_fault("TorqueSensor_ChA")
            time.sleep(1)

        return results