How to unit test node-cron job

Question

I need to call a function using node-cron and want to write a unit test case for that. the unit test case should be able to test if the function is getting calling based on the pattern.

Below is my code

const server = (module.exports = {
  cronJob: null,
  scheduledJob: function(pattern) {
    server.cronJob = cron.schedule(pattern, () => {
      server.run();
    });
  },
  run: function() {
    console.log("run called");
  },
}); 

describe("entry point test suite", () => {
  it("should call function every second", (done) => {
    const pattern = "* * * * * *";
    let spy = sinon.spy(server, "run");
    server.scheduledJob(pattern);
    server.cronJob.Start();
    // to do wait for 3 sencond
    server.cronJob.Stop();
    expect(spy.callCount).eq(3);
  });
}); 

Two questions:

1. other than setTimeout what option I have to wait for 3 seconds so that cron job will run 3 times as pattern is for each second.

2. This test is failing with error server.cronjob.start is not a function.

How can I make this work?

Answer 1

Here is the unit testing solution:

server.js:

const cron = require("node-cron");

const server = (module.exports = {
  cronJob: null,
  scheduledJob: function(pattern) {
    server.cronJob = cron.schedule(pattern, () => {
      server.run();
    });
  },
  run: function() {
    console.log("run called");
  },
});

server.test.js:

const server = require("./server");
const sinon = require("sinon");
const cron = require("node-cron");
const { expect } = require("chai");

describe("57208090", () => {
  afterEach(() => {
    sinon.restore();
  });
  describe("#scheduledJob", () => {
    it("should schedule job", () => {
      const pattern = "* * * * * *";
      const runStub = sinon.stub(server, "run");
      const scheduleStub = sinon
        .stub(cron, "schedule")
        .yields()
        .returns({});
      server.scheduledJob(pattern);
      sinon.assert.calledWith(scheduleStub, pattern, sinon.match.func);
      sinon.assert.calledOnce(runStub);
      expect(server.cronJob).to.be.eql({});
    });
  });

  describe("#run", () => {
    it("should run server", () => {
      const logSpy = sinon.spy(console, "log");
      server.run();
      sinon.assert.calledWith(logSpy, "run called");
    });
  });
});

Unit test result with 100% coverage:

  57208090
    #scheduledJob
      ✓ should schedule job
    #run
run called
      ✓ should run server


  2 passing (12ms)

----------------|----------|----------|----------|----------|-------------------|
File            |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
----------------|----------|----------|----------|----------|-------------------|
All files       |      100 |      100 |      100 |      100 |                   |
 server.js      |      100 |      100 |      100 |      100 |                   |
 server.test.js |      100 |      100 |      100 |      100 |                   |
----------------|----------|----------|----------|----------|-------------------|

You asked for unit testing. If you need an integration testing, please create a new post.

Source code: https://github.com/mrdulin/mocha-chai-sinon-codelab/tree/master/src/stackoverflow/57208090