# Resilience Tests

### NFT-RES-01: FC IMU-only fallback after >3 s without estimate

**Summary**: Validates AC-5.2 — on >3 s without an estimate, the FC falls back to IMU-only dead reckoning AND the SUT logs the failure.
**Traces to**: AC-5.2

**Preconditions**:
- SUT in `satellite_anchored` steady state on Derkachi replay.
- 4 s outage injector primed (replay paused for 4 s of wall-clock).

**Fault injection**:
- Pause frame source for 4 s of wall-clock while FC IMU stream continues.

**Steps**:

| Step | Action | Expected Behavior |
|------|--------|------------------|
| 1 | Mid-replay, halt frame delivery for 4 s | SUT continues emitting `dead_reckoned` estimates from FC IMU/attitude propagation |
| 2 | After 3 s without an emit (i.e. SUT internally fails to update for >3 s), SUT logs `NO_ESTIMATE_TIMEOUT` | FDR contains the log entry |
| 3 | Observe FC EKF source-set transition | EKF source-set transitions to internal IMU-only on the FC side per the FC's own failsafe logic (AP `EKF_FAILSAFE` or equivalent on iNav) |
| 4 | Resume frame delivery | SUT recovers; FC EKF source-set returns to companion-GPS source |

**Pass criteria**:
- `NO_ESTIMATE_TIMEOUT` logged within 200 ms of the 3 s mark.
- FC EKF reflects the transition.
- Recovery on resume happens within 5 emit cycles.

---

### NFT-RES-02: Companion mid-flight reboot

**Summary**: Validates AC-5.3 — on companion reboot mid-flight, SUT re-initializes from FC's current IMU-extrapolated position.
**Traces to**: AC-5.3

**Preconditions**:
- SUT in steady state on Derkachi replay.
- FC SITL has been running long enough to have a stable IMU-extrapolated pose.

**Fault injection**:
- `docker compose restart gps-denied-onboard` mid-replay (or `systemctl restart` on Tier-2).

**Steps**:

| Step | Action | Expected Behavior |
|------|--------|------------------|
| 1 | At t=120 s of replay, restart SUT container | SUT goes down and back up |
| 2 | Wait for first post-restart `GPS_INPUT` / `MSP2_SENSOR_GPS` arrival | First emit lat/lon within ±100 m of FC's IMU-extrapolated pose at boot-complete time |
| 3 | Observe TTFF post-reboot | Within AC-NEW-1 budget (<30 s p95) |

**Pass criteria**:
- First post-restart emit ±100 m of FC pose at boot-complete.
- Cold-restart TTFF < 30 s.
- No FC-side EKF divergence event during the gap.

---

### NFT-RES-03: False-position safety budget Monte Carlo

**Summary**: Validates AC-NEW-4 false-position safety budget (`P(error > 500 m) < 0.1%`, `P(error > 1 km) < 0.01%`) on the available data + synthesis. PARTIAL — multi-flight statistics constrained by single Derkachi flight + 60 stills (see traceability matrix flag).
**Traces to**: AC-NEW-4 (PARTIAL)

**Preconditions**:
- Tier-1 acceptable (statistical rather than hardware-bound).
- Pull together: 60 still-image runs (60 frames) + Derkachi replay (~14,700 frames at 30 fps OR resampled to ~870 frames at 3 Hz target). Total ≥930 frames per Monte Carlo iteration.
- Run M=50 Monte Carlo iterations with synthetic perturbations (camera-pose noise, IMU bias drift, randomized tile sub-selection).

**Fault injection**:
- Add per-iteration synthetic perturbations to mimic a population of independent flights.

**Steps**:

| Step | Action | Expected Behavior |
|------|--------|------------------|
| 1 | Run M iterations end-to-end | Per-iteration error distribution captured |
| 2 | Aggregate across all iterations × frames | Per-frame error CDF |
| 3 | Read off `P(error > 500 m)` and `P(error > 1 km)` from CDF | Both values |

**Pass criteria** (PARTIAL):
- `P(error > 500 m) < 0.1%`.
- `P(error > 1 km) < 0.01%`.
- Test FAILS-OPEN with explicit "PARTIAL" annotation in CSV report when iteration count is below the AC-NEW-4-implied ≥100 flights — noted as reduced confidence pending D-PROJ-3 (AerialVL S03 + own multi-flight data).

---

### NFT-RES-04: Visual blackout + spoof degraded-mode escalation

**Summary**: Validates the AC-NEW-8 escalation ladder (5 s, 15 s, 35 s blackouts paired with spoof) including the 100 m / 500 m covariance thresholds and the 10 s GPS-health gate before recovery.
**Traces to**: AC-NEW-8 (twin of FT-N-04 with extended duration window and covariance assertions)

**Preconditions**: Same as FT-N-04; Tier-1 acceptable.

**Fault injection**: `blackout-spoof-derkachi` 5 s / 15 s / 35 s windows + spoofed FC GPS for the same windows.

**Steps**:

| Step | Action | Expected Behavior |
|------|--------|------------------|
| 1 | Begin 5 s window | Mode transition ≤ 400 ms; covariance grows monotonically; spoofed GPS rejected |
| 2 | At end of 5 s window, attempt recovery | Recovery only after FC GPS-health stable + non-spoofed for ≥10 s AND visual/satellite consistency check succeeds (gate enforced) |
| 3 | Begin 15 s window | Same as step 1 plus when 95% covariance crosses 100 m: outbound MAVLink fix-quality degraded to "2D fix or worse" |
| 4 | Begin 35 s window | Plus when 95% covariance crosses 500 m OR blackout exceeds 30 s: `horiz_accuracy=999.0` + `VISUAL_BLACKOUT_FAILSAFE` STATUSTEXT emitted |

**Pass criteria**:
- All four assertions fire at the right thresholds.
- Recovery gate is honored — early recovery attempts (FC GPS healthy for <10 s) MUST NOT promote spoofed GPS back into the estimator.

**Duration**: ~10 min total for three windows.