Rewrite WallClockListener as onTimeTravel

ts/test-both/util/startTimeTravelDetector_test.ts

@@ -0,0 +1,59 @@
+// Copyright 2022 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import * as sinon from 'sinon';
+
+import { startTimeTravelDetector } from '../../util/startTimeTravelDetector';
+
+describe('startTimeTravelDetector', () => {
+  let sandbox: sinon.SinonSandbox;
+
+  beforeEach(() => {
+    sandbox = sinon.createSandbox({ useFakeTimers: true });
+  });
+
+  afterEach(() => {
+    sandbox.restore();
+  });
+
+  it('calls the callback when the time between checks is more than 2 seconds', async function test() {
+    const callback = sandbox.fake();
+
+    startTimeTravelDetector(callback);
+
+    // Normal clock behavior
+    await sandbox.clock.tickAsync(1234);
+    await sandbox.clock.tickAsync(5678);
+    sinon.assert.notCalled(callback);
+
+    // Time travel ≤2s
+    sandbox.clock.setSystemTime(Date.now() + 1000);
+    await sandbox.clock.tickAsync(1000);
+    sinon.assert.notCalled(callback);
+    sandbox.clock.setSystemTime(Date.now() + 1999);
+    await sandbox.clock.tickAsync(1);
+    sinon.assert.notCalled(callback);
+
+    // Time travel >2s
+    sandbox.clock.setSystemTime(Date.now() + 2001);
+    await sandbox.clock.nextAsync();
+    sinon.assert.calledOnce(callback);
+    sandbox.clock.setSystemTime(Date.now() + 9999);
+    await sandbox.clock.nextAsync();
+    sinon.assert.calledTwice(callback);
+
+    // Normal clock behavior
+    await sandbox.clock.tickAsync(9876);
+    sinon.assert.calledTwice(callback);
+  });
+
+  it('can detect time travel right after initialization', async () => {
+    const callback = sandbox.fake();
+
+    startTimeTravelDetector(callback);
+
+    sandbox.clock.setSystemTime(Date.now() + 2001);
+    await sandbox.clock.nextAsync();
+    sinon.assert.calledOnce(callback);
+  });
+});