1 files changed, 96 insertions, 0 deletions
diff --git a/js/xpconnect/tests/mochitest/finalizationRegistry_worker.js b/js/xpconnect/tests/mochitest/finalizationRegistry_worker.js
new file mode 100644
index 0000000000..d603cdab38
--- /dev/null
+++ b/js/xpconnect/tests/mochitest/finalizationRegistry_worker.js
@@ -0,0 +1,96 @@
+let holdings1 = [];
+let holdings2 = [];
+let holdings3 = [];
+let holdings4 = [];
+let holdings5 = [];
+
+onmessage = (event) => {
+  switch (event.data) {
+  case 'startTest':
+    startTest();
+    break;
+  case 'checkResults':
+    checkResults();
+    break;
+  default:
+    throw "Unknown message";
+  }
+};
+
+function startTest() {
+  // Registry with no registered objects.
+  let registry1 = new FinalizationRegistry(v => { holdings1.push(v); });
+
+  // Registry with three registered objects.
+  let registry2 = new FinalizationRegistry(v => { holdings2.push(v); });
+  registry2.register({}, 1);
+  registry2.register({}, 2);
+  registry2.register({}, 3);
+
+  // Registry with registered object that is then unregistered.
+  let registry3 = new FinalizationRegistry(v => { holdings3.push(v); });
+  let token3 = {}
+  registry3.register({}, 1, token3);
+  registry3.unregister(token3);
+
+  // Registry with registered object that doesn't die.
+  let registry4 = new FinalizationRegistry(v => { holdings4.push(v); });
+  let object4 = {};
+  registry4.register(object4, 1);
+
+  // Registry observing cyclic JS data structure.
+  let registry5 = new FinalizationRegistry(v => { holdings5.push(v); });
+  registry5.register(makeJSCycle(4), 5);
+
+  const { gc } = getJSTestingFunctions();
+  gc();
+
+  Promise.resolve().then(() => {
+    checkNoCallbacks();
+  });
+
+  postMessage('started');
+}
+
+function checkNoCallbacks() {
+  is(holdings1.length, 0);
+  is(holdings2.length, 0);
+  is(holdings3.length, 0);
+  is(holdings4.length, 0);
+  is(holdings5.length, 0);
+}
+
+function checkResults() {
+  is(holdings1.length, 0);
+
+  let result = holdings2.sort((a, b) => a - b);
+  is(result.length, 3);
+  is(result[0], 1);
+  is(result[1], 2);
+  is(result[2], 3);
+
+  is(holdings3.length, 0);
+  is(holdings4.length, 0);
+
+  is(holdings5.length, 1);
+  is(holdings5[0], 5);
+
+  postMessage('passed');
+}
+
+function is(a, b) {
+  if (a !== b) {
+    throw `Expected ${b} but got ${a}`;
+  }
+}
+
+function makeJSCycle(size) {
+  let first = {};
+  let current = first;
+  for (let i = 0; i < size; i++) {
+    current.next = {};
+    current = current.next;
+  }
+  current.next = first;
+  return first;
+}