before functional changes by codex

test/edge/missing-child.edge.test.js

@@ -0,0 +1,28 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const NodeClass = require('../../src/nodeClass');
+const { makeNodeStub, makeREDStub } = require('../helpers/factories');
+
+test('registerChild with unknown node id currently throws (known robustness gap)', () => {
+  const inst = Object.create(NodeClass.prototype);
+  const node = makeNodeStub();
+
+  inst.node = node;
+  inst.RED = makeREDStub();
+  inst.source = {
+    childRegistrationUtils: {
+      registerChild() {},
+    },
+  };
+
+  inst._attachInputHandler();
+
+  assert.throws(() => {
+    node._handlers.input(
+      { topic: 'registerChild', payload: 'missing-child', positionVsParent: 'upstream' },
+      () => {},
+      () => {},
+    );
+  });
+});