updates

test/integration/registration.integration.test.js

@@ -25,3 +25,29 @@ test('registerChild listens to measurement events and stores measured pressure',
   assert.equal(typeof stored, 'number');
   assert.equal(Math.round(stored), 123);
 });
+
+test('registerChild deduplicates listeners on re-registration', async () => {
+  const machine = new Machine(makeMachineConfig(), makeStateConfig());
+  const child = makeChildMeasurement({ id: 'pt-dup', positionVsParent: 'downstream', type: 'pressure', unit: 'mbar' });
+  const eventName = 'pressure.measured.downstream';
+
+  let handlerCalls = 0;
+  const originalUpdatePressure = machine.updateMeasuredPressure.bind(machine);
+  machine.updateMeasuredPressure = (...args) => {
+    handlerCalls += 1;
+    return originalUpdatePressure(...args);
+  };
+
+  machine.registerChild(child, 'measurement');
+  machine.registerChild(child, 'measurement');
+
+  assert.equal(child.measurements.emitter.listenerCount(eventName), 1);
+
+  child.measurements
+    .type('pressure')
+    .variant('measured')
+    .position('downstream')
+    .value(321, Date.now(), 'mbar');
+
+  assert.equal(handlerCalls, 1);
+});