The Sinon stub appears to be completely ignored during the test, despite its successful use in earlier tests

Question

The Sinon stub appears to be completely ignored during the test, despite its successful use in earlier tests

I am currently testing the functionality of an express router using sinon. The first test in my code below passes without any issues, but I'm having trouble with the second test. It's not passing and I can't seem to figure out why.

When I send an http request to the route, it works as expected.

There seems to be some issue with the catch block causing the problem. Below is the code snippet that I have narrowed it down to, along with the error message:

books.js

import express from 'express';
import models from '../db/models';
const router = express.Router();

var indexPost = async (req, res, next) => {
  try {
    let savedBook = await models.Book.create({
      title: req.body.title || null,
      isbn: req.body.isbn || null,
      author: req.body.author || null
    });
    res.status(201).json({ book: savedBook.id });
  } catch (err) {
    res.status(400).send('');
  }
};
router.post('/', indexPost);

export default router;
export { indexPost };

books.test.js

import { indexPost } from '../../../src/routes/books';
import models from '../../../src/db/models';
import sinon from 'sinon';
import { expect } from 'chai';
import sinonTestFactory from 'sinon-test';

const sinonTest = sinonTestFactory(sinon);

describe('Books router', () => {
  describe('indexPost', () => {
    it('should save the book to the database', sinonTest(async function () {
      let req = {
        body: {
          title: 'Book Title',
          isbn: '123asera23',
          author: 123
        }
      };

      let res = {
        status: status => {},
        json: json => {}
      };

      this.stub(res, 'status').returns(res);
      this.stub(res, 'json').returns(res);

      indexPost(req, res);

      let book = await models.Key.findById(1);

      expect(book.title).to.equal('Book Title');
      expect(book.isbn).to.equal('123asera23');
      expect(book.author).to.equal(123);

      sinon.assert.calledWith(res.status, 201);
      sinon.assert.calledWith(res.json, { book: 1 });
    }));

    it('should throw an error if data is not all there', sinonTest(async function () {
      let req = {
        body: {
          title: 'Book Title',
          author: 123
        }
      };

      let res = {
        status: status => {},
        send: send => {}
      };

      this.stub(res, 'status').returns(res);
      this.stub(res, 'send').returns(res);

      indexPost(req, res);

      sinon.assert.calledWith(res.status, 400);
      sinon.assert.calledWith(res.send, '');
    }));
  });
});

Error

1) Books router
    indexPost
        should throw an error if data is not all there:
            AssertError: expected status to be called with arguments
            at Object.fail (/var/app/node_modules/sinon/lib/sinon/assert.js:96:21)
            at failAssertion (/var/app/node_modules/sinon/lib/sinon/assert.js:55:16)
            at Object.assert.(anonymous function) [as calledWith] (/var/app/node_modules/sinon/lib/sinon/assert.js:80:13)
            at Context.<anonymous> (tests/src/routes/books.test.js:58:20)
            at Generator.next (<anonymous>)
            at step (tests/src/routes/books.test.js:21:191)
            at tests/src/routes/keys.test.js:21:437
            at new Promise (<anonymous>)
            at Context.<anonymous> (tests/src/routes/books.test.js:21:99)
            at callSandboxedFn (/var/app/node_modules/sinon-test/lib/test.js:94:25)
            at Context.sinonSandboxedTest (/var/app/node_modules/sinon-test/lib/test.js:114:24)

javascript unit-testing express mocha.js sinon

Answer 1

Answer №1

Upon realizing that the solution was not as straightforward as initially thought, I took the time to figure out the correct answer.

The issue stemmed from my incorrect approach to handling non-async code within JavaScript.

I needed to ensure that my controller returned a promise to Mocha's it function. To achieve this, the controller itself had to return a promise, especially when dealing with database operations where the database call itself could be returned as a promise.

After the promise resolves with either resolve or reject, assertions can be made to verify the success of the tests.

The key lies in chaining promises all the way from the bottom of the controller back up to Mocha's it function.

Below is the revised code to address this:

import express from 'express';
import models from '../db/models';
const router = express.Router();

var indexPost = (req, res, next) => {
  return models.Book.create({
    title: req.body.title || null,
    isbn: req.body.isbn || null,
    author: req.body.author || null
  }).then(savedBook => {
    res.status(201).json({ book: savedBook.id });
  }).catch(err => {
    res.status(400).send('');
  });
};
router.post('/', indexPost);

export default router;
export { indexPost };

import { indexPost } from '../../../src/routes/books';
import models from '../../../src/db/models';
import sinon from 'sinon';
import { expect } from 'chai';

describe('Books router', () => {
  describe('indexPost', () => {
    it('should save the book to the database', async () => {
      let req = {
        body: {
          title: 'Book Title',
          isbn: '123asera23',
          author: 123
        }
      };

      const jsonStub = sinon.stub()
      const res = { status: status => ({ json: jsonStub, send: err => err }) }
      const statusSpy = sinon.spy(res, 'status')

      return indexPost(req, res).then(() => {
        let book = await models.Key.findById(1);

        expect(book.title).to.equal('Book Title');
        expect(book.isbn).to.equal('123asera23');
        expect(book.author).to.equal(123);

        sinon.assert.calledWith(res.status, 201);
        sinon.assert.calledWith(res.json, { book: 1 });
      })
    }));

    it('should throw an error if data is not all there', () => {
      let req = {
        body: {
          title: 'Book Title',
          author: 123
        }
      };

      const sendStub = sinon.stub()
      const res = { status: status => ({ json: err => err, send: sendStub }) }
      const statusSpy = sinon.spy(res, 'status')

      indexPost(req, res).then(() => {
        sinon.assert.calledWith(res.status, 400);
        sinon.assert.calledWith(res.send, '');
      });
    }));
  });
});

The response object quirks have also been resolved in the updated code above.

Answer 2

Upon realizing that the solution was not as straightforward as initially thought, I took the time to figure out the correct answer.

The issue stemmed from my incorrect approach to handling non-async code within JavaScript.

I needed to ensure that my controller returned a promise to Mocha's it function. To achieve this, the controller itself had to return a promise, especially when dealing with database operations where the database call itself could be returned as a promise.

After the promise resolves with either resolve or reject, assertions can be made to verify the success of the tests.

The key lies in chaining promises all the way from the bottom of the controller back up to Mocha's it function.

Below is the revised code to address this:

import express from 'express';
import models from '../db/models';
const router = express.Router();

var indexPost = (req, res, next) => {
  return models.Book.create({
    title: req.body.title || null,
    isbn: req.body.isbn || null,
    author: req.body.author || null
  }).then(savedBook => {
    res.status(201).json({ book: savedBook.id });
  }).catch(err => {
    res.status(400).send('');
  });
};
router.post('/', indexPost);

export default router;
export { indexPost };

import { indexPost } from '../../../src/routes/books';
import models from '../../../src/db/models';
import sinon from 'sinon';
import { expect } from 'chai';

describe('Books router', () => {
  describe('indexPost', () => {
    it('should save the book to the database', async () => {
      let req = {
        body: {
          title: 'Book Title',
          isbn: '123asera23',
          author: 123
        }
      };

      const jsonStub = sinon.stub()
      const res = { status: status => ({ json: jsonStub, send: err => err }) }
      const statusSpy = sinon.spy(res, 'status')

      return indexPost(req, res).then(() => {
        let book = await models.Key.findById(1);

        expect(book.title).to.equal('Book Title');
        expect(book.isbn).to.equal('123asera23');
        expect(book.author).to.equal(123);

        sinon.assert.calledWith(res.status, 201);
        sinon.assert.calledWith(res.json, { book: 1 });
      })
    }));

    it('should throw an error if data is not all there', () => {
      let req = {
        body: {
          title: 'Book Title',
          author: 123
        }
      };

      const sendStub = sinon.stub()
      const res = { status: status => ({ json: err => err, send: sendStub }) }
      const statusSpy = sinon.spy(res, 'status')

      indexPost(req, res).then(() => {
        sinon.assert.calledWith(res.status, 400);
        sinon.assert.calledWith(res.send, '');
      });
    }));
  });
});

The response object quirks have also been resolved in the updated code above.

The Sinon stub appears to be completely ignored during the test, despite its successful use in earlier tests

Answer №1

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