test(daemon): use fake timers and mock date to test daemon

Make tests more predictable by not actually having to wait a real amount of time.

Author: danielrbradley

CronDaemon.ts

@@ -1,8 +1,8 @@
 import { parse, Schedule } from "./parse";
 import { next } from "./next";
 
-// When delay is larger than 2147483647 or less than 1, the delay will be set to 1.
-const MAX_DELAY = Math.pow(2, 32 - 1) - 1;
+// When delay is larger than `(2^31) - 1)` the delay will be set to 1.
+const MAX_DELAY = 2147483647;
 
 /**
  * Calculate the next time to execute the job.

package.json

@@ -44,9 +44,13 @@
     "babel-jest": "^26.6.1",
     "commitizen": "^4.2.2",
     "jest": "^26.6.1",
+    "mockdate": "^3.0.2",
     "rimraf": "^3.0.2",
     "semantic-release": "^17.2.2",
     "typedoc": "^0.19.2",
     "typescript": "^4.0.5"
+  },
+  "jest": {
+    "timers": "modern"
   }
 }

tests/CronDaemon.test.ts

@@ -1,80 +1,143 @@
+import MockDate from "mockdate";
 import { CronDaemon } from "../CronDaemon";
 
-const waitFor = (ms: number) =>
-  new Promise((resolve, reject) => {
-    setTimeout(resolve, ms);
-  });
+let daemon: CronDaemon | undefined;
+
+beforeAll(() => {
+  MockDate.set(Date.now());
+});
+afterEach(() => {
+  if (daemon) {
+    daemon.stop();
+    daemon = undefined;
+  }
+});
+afterAll(() => {
+  MockDate.reset();
+});
 
 test("triggering", async () => {
   const callback = jest.fn();
-  const daemon = new CronDaemon("* * * * * * *", callback);
+  daemon = new CronDaemon("* * * * * * *", callback);
+
   expect(daemon.state()).toEqual("running");
   expect(callback).not.toHaveBeenCalled();
-  await waitFor(1000);
+
+  MockDate.set(Date.now() + 1000);
+  jest.advanceTimersByTime(1000);
+
   expect(callback).toHaveBeenCalledTimes(1);
 });
 
 test("schedule without next date", async () => {
   const callback = jest.fn();
-  const daemon = new CronDaemon("* * * * * * 1980", callback);
+  daemon = new CronDaemon("* * * * * * 1980", callback);
+
   expect(daemon.next()).toBeUndefined();
-  await waitFor(1000);
+
+  MockDate.set(Date.now() + 1000);
+  jest.advanceTimersByTime(1000);
+
   expect(callback).not.toHaveBeenCalled();
 });
 
 test("calling start multiple times", async () => {
   const callback = jest.fn();
-  const daemon = new CronDaemon("* * * * * * *", callback);
+  daemon = new CronDaemon("* * * * * * *", callback);
+
   daemon.start();
   daemon.start();
+
   expect(daemon.state()).toEqual("running");
   expect(callback).not.toHaveBeenCalled();
-  await waitFor(1000);
+
+  MockDate.set(Date.now() + 1000);
+  jest.advanceTimersByTime(1000);
+
   expect(callback).toHaveBeenCalledTimes(1);
 });
 
 test("stopping", async () => {
   const callback = jest.fn();
-  const daemon = new CronDaemon("* * * * * * *", callback);
+  daemon = new CronDaemon("* * * * * * *", callback);
+
   daemon.stop();
+
   expect(daemon.state()).toEqual("stopped");
-  await waitFor(1000);
+
+  MockDate.set(Date.now() + 1000);
+  jest.advanceTimersByTime(1000);
+
   expect(callback).not.toHaveBeenCalled();
 });
 
 test("doesn't break when next trigger is a long way away", async () => {
   const callback = jest.fn();
-  const daemon = new CronDaemon("* * * * * * 2099", callback);
+  daemon = new CronDaemon("* * * * * * 2099", callback);
+
   expect(daemon.state()).toEqual("running");
-  await waitFor(50);
+
+  MockDate.set(Date.now() + 50);
+  jest.advanceTimersByTime(50);
+
   expect(callback).not.toHaveBeenCalled();
 });
 
 test("can call stop multiple times", async () => {
   const callback = jest.fn();
-  const daemon = new CronDaemon("* * * * * * *", callback);
+  daemon = new CronDaemon("* * * * * * *", callback);
+
   daemon.stop();
   daemon.stop();
+
   expect(daemon.state()).toEqual("stopped");
   expect(callback).not.toHaveBeenCalled();
 });
 
 test("custom date function", async () => {
   const callback = jest.fn();
-  const daemon = new CronDaemon((now) => {
+  daemon = new CronDaemon((now) => {
     const next = new Date(now);
     next.setTime(now.getTime() + 10);
     return next;
   }, callback);
-  await waitFor(20);
+
+  MockDate.set(Date.now() + 50);
+  jest.advanceTimersByTime(20);
+
   expect(callback).toHaveBeenCalled();
 });
 
 test("Invalid schedule type causes an error", () => {
+  const callback = jest.fn();
   try {
-    new CronDaemon({} as any, jest.fn());
+    daemon = new CronDaemon({} as any, callback);
     throw new Error("Should have failed validation");
   } catch (error) {
     expect(error.message).toEqual("Invalid schedule type");
+    expect(callback).not.toHaveBeenCalled();
   }
 });
+
+test("Very long delay", () => {
+  const maxDelay = Math.pow(2, 32 - 1) - 1;
+  const requestedDelay = maxDelay * 1.5;
+  const start = Date.now();
+  MockDate.set(start);
+
+  const callback = jest.fn();
+  daemon = new CronDaemon(
+    (now) => new Date(now.getTime() + requestedDelay),
+    callback
+  );
+
+  jest.runOnlyPendingTimers();
+  MockDate.set(start + maxDelay);
+
+  expect(callback).not.toHaveBeenCalled();
+
+  MockDate.set(start + requestedDelay);
+  jest.runOnlyPendingTimers();
+
+  expect(callback).toHaveBeenCalledTimes(1);
+});

yarn.lock

@@ -5596,6 +5596,11 @@ mkdirp@~1.0.3:
   resolved "https://registry.yarnpkg.com/mkdirp/-/mkdirp-1.0.4.tgz#3eb5ed62622756d79a5f0e2a221dfebad75c2f7e"
   integrity sha512-vVqVZQyf3WLx2Shd0qJ9xuvqgAyKPLAiqITEtqW0oIUjzo3PePDd6fW9iFz30ef7Ysp/oiWqbhszeGWW2T6Gzw==
 
+mockdate@^3.0.2:
+  version "3.0.2"
+  resolved "https://registry.yarnpkg.com/mockdate/-/mockdate-3.0.2.tgz#a5a7bb5820da617747af424d7a4dcb22c6c03d79"
+  integrity sha512-ldfYSUW1ocqSHGTK6rrODUiqAFPGAg0xaHqYJ5tvj1hQyFsjuHpuWgWFTZWwDVlzougN/s2/mhDr8r5nY5xDpA==
+
 modify-values@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/modify-values/-/modify-values-1.0.1.tgz#b3939fa605546474e3e3e3c63d64bd43b4ee6022"