Improve generator control and status displays

tests/test_simulation.py

@@ -206,6 +206,30 @@ def test_generator_spools_and_powers_pumps():
     assert state.primary_loop.mass_flow_rate > 0.0
 
 
+def test_generator_manual_mode_allows_single_unit_and_stop():
+    reactor = Reactor.default()
+    state = reactor.initial_state()
+    reactor.shutdown = False
+    reactor.control.manual_control = True
+    reactor.control.rod_fraction = 0.95
+    reactor.generator_auto = False
+    reactor.primary_pump_units = [True, False]
+    reactor.secondary_pump_units = [False, False]
+
+    reactor.step(state, dt=1.0, command=ReactorCommand(generator_units={1: True}, primary_pumps={1: True}))
+    assert state.generators[0].starting or state.generators[0].running
+
+    for _ in range(15):
+        reactor.step(state, dt=1.0)
+
+    assert state.generators[0].running is True
+    reactor.step(state, dt=1.0, command=ReactorCommand(generator_units={1: False}))
+    for _ in range(5):
+        reactor.step(state, dt=1.0)
+    assert state.generators[0].running is False
+    assert state.generators[1].running is False
+
+
 def test_meltdown_triggers_shutdown():
     reactor = Reactor.default()
     state = reactor.initial_state()