Improve persistence and reactor dynamics

tests/test_neutronics.py

@@ -0,0 +1,26 @@
+from reactor_sim.neutronics import NeutronDynamics
+from reactor_sim.state import CoreState
+
+
+def _core_state(
+    temperature: float = 950.0,
+    flux: float = 2e7,
+    burnup: float = 0.01,
+    power: float = 500.0,
+) -> CoreState:
+    return CoreState(
+        fuel_temperature=temperature,
+        neutron_flux=flux,
+        reactivity_margin=0.0,
+        power_output_mw=power,
+        burnup=burnup,
+    )
+
+
+def test_reactivity_increases_with_rod_withdrawal():
+    dynamics = NeutronDynamics()
+    state = _core_state()
+    rho_full_out = dynamics.reactivity(state, control_fraction=0.0)
+    rho_half = dynamics.reactivity(state, control_fraction=0.5)
+    assert rho_full_out > 0.0
+    assert rho_full_out > rho_half

tests/test_simulation.py

@@ -4,6 +4,7 @@ from pathlib import Path
 import pytest
 
 from reactor_sim import constants
+from reactor_sim.failures import HealthMonitor
 from reactor_sim.reactor import Reactor
 from reactor_sim.simulation import ReactorSimulation
 
@@ -13,7 +14,7 @@ def test_reactor_initial_state_is_cold():
     state = reactor.initial_state()
     assert state.core.fuel_temperature == constants.ENVIRONMENT_TEMPERATURE
     assert state.primary_loop.mass_flow_rate == 0.0
-    assert state.turbine.electrical_output_mw == 0.0
+    assert state.total_electrical_output() == 0.0
 
 
 def test_state_save_and_load_roundtrip(tmp_path: Path):
@@ -36,7 +37,18 @@ def test_health_monitor_flags_core_failure():
     reactor = Reactor.default()
     state = reactor.initial_state()
     state.core.fuel_temperature = constants.MAX_CORE_TEMPERATURE
-    failures = reactor.health_monitor.evaluate(state, True, True, True, dt=200.0)
+    failures = reactor.health_monitor.evaluate(state, True, True, [True, True, True], dt=200.0)
     assert "core" in failures
     reactor._handle_failure("core")
     assert reactor.shutdown is True
+
+
+def test_maintenance_recovers_component_health():
+    monitor = HealthMonitor()
+    pump = monitor.component("secondary_pump")
+    pump.integrity = 0.3
+    pump.fail()
+    restored = monitor.maintain("secondary_pump", amount=0.5)
+    assert restored is True
+    assert pump.integrity == pytest.approx(0.8)
+    assert pump.failed is False