commit stale changes

components/pid/TODO.md

@@ -32,17 +32,19 @@ git history for `temp_controller.py`/`temp_controller_smith.py`).
   hold_scale)` — the overshoot-compensation scheduling logic now lives
   entirely in the temp controller, not the generic `Pid` block.
 
-- [ ] **No automated tests for the heat-rate filtering or Smith
-  correction specifically.** An earlier `tests/components/pid/` suite
-  (stdlib `unittest`, no pytest) covering FSM transitions, anti-windup
-  clamping, and Kalman convergence was removed before the Kalman-filter
-  removal/Smith rewrite. A new `tests/components/pid/` suite was added
-  alongside the HOLD-windup fix below (`test_pid.py`,
-  `test_temp_controller_closed_loop.py`) covering the `yi_max` clamp and
-  closed-loop disturbance/ramp/transition behavior, but
-  `_compute_heatrate()`'s backward-difference + low-pass filtering and
-  the two-model Smith correction itself still have no dedicated
-  coverage. This drives a physical heater — worth extending.
+- [x] **No automated tests for the heat-rate filtering or Smith
+  correction specifically.** Fixed: `tests/components/pid/test_heatrate_filter.py`
+  covers `_compute_heatrate()` - a first-tick-reads-zero regression test
+  (verified it would catch the old hardcoded `last_theta_ist = 20` bug),
+  convergence to the true rate on a steady ramp (heating and cooling),
+  and the `beta` pre-filter measurably suppressing noise amplification vs.
+  raw differentiation. `tests/components/pid/test_temp_controller_smith_correction.py`
+  covers the two-model correction in `temp_controller_smith.py`: with a
+  matched internal model, `theta_ist` stays close to the fast (zero-delay)
+  model's own prediction (contrasted against a deliberately mismatched
+  model, which diverges 10x+ further); and the corrected estimate visibly
+  rises before the real transport delay (`Td`) has elapsed, while the raw
+  plant reading is still flat.
 
 - [x] **`set_model_power` isn't defined on every controller, but
   `brewpi.py` wires it unconditionally.** Fixed: `TempControllerBase`