Testing the Mongoose save() method by mocking it in an integration test

Question

Testing the Mongoose save() method by mocking it in an integration test

I am currently facing an issue while trying to create a test scenario. The problem arises with the endpoint I have for a REST-API:

Post represents a Mongoose model.

router.post('/addPost', (req, res) => {
  const post = new Post(req.body);
  post.save()
    .then(() => ... return success)
    .catch((err) => ... return error);
});

My goal is to write a test that verifies if the correct value is returned when save() resolves.

After attempting to mock the save() method within the model, I realized it may not be possible. As mentioned in this thread , save is not a method on the model itself but on the document (an instance of the model).

Even after following the recommended approach from the above-mentioned discussion, I seem to be missing something as I cannot successfully override the save() method.

The code snippet I have so far (factory is sourced from factory-girl as per the instructions provided in the given link. Here is a direct link to the package):

factory.define('Post', Post, {
  save: new Promise((resolve, reject) => {
    resolve();
  }),
});
factory.build('Post').then((factoryPost) => {
  Post = factoryPost;
  PostMock = sinon.mock(Post);
  PostMock.expects('save').resolves({});

  ... perform test
});

I believe my implementation might be off track, but I am unable to pinpoint where I am going wrong. There must be others who have encountered a similar issue before.

javascript unit-testing mongoose promise sinon

Answer 1

Answer №1

If you want to create a stub for the post document, which represents an instance of the Post model, you can achieve this by stubbing the Post.prototype.

For example:

server.ts:

import express from 'express';
import Post from './models/post';
import http from 'http';

const app = express();
app.post('/addPost', async (req, res) => {
  const post = new Post(req.body);
  await post.save();
  res.sendStatus(200);
});

const server = http.createServer(app).listen(3000, () => {
  console.info('Http server is listening on http://localhost:3000');
});

export { server };

models/post.ts:

import { model, Schema } from 'mongoose';

const postSchema = new Schema({
  titie: String,
});

export default model('post', postSchema);

server.integration.spec.ts:

import { server } from './server';
import request from 'supertest';
import Post from './models/post';
import sinon from 'sinon';
import { expect } from 'chai';

after((done) => {
  server.close(done);
});

describe('58820254', () => {
  it('/addPost', (done) => {
    const saveStub = sinon.stub(Post.prototype, 'save').returnsThis();
    request(server)
      .post('/addPost')
      .expect(() => {
        console.log('assert');
        expect(saveStub.calledOnce).to.be.true;
      })
      .expect(200, done);
  });
});

Integration test with full coverage:

Http server is listening on http://localhost:3000
  58820254
assert
    ✓ /addPost


  1 passing (25ms)

-----------------------------|----------|----------|----------|----------|-------------------|
File                         |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------------------------|----------|----------|----------|----------|-------------------|
All files                    |      100 |      100 |      100 |      100 |                   |
 58820254                    |      100 |      100 |      100 |      100 |                   |
  server.integration.spec.ts |      100 |      100 |      100 |      100 |                   |
  server.ts                  |      100 |      100 |      100 |      100 |                   |
 58820254/models             |      100 |      100 |      100 |      100 |                   |
  post.ts                    |      100 |      100 |      100 |      100 |                   |
-----------------------------|----------|----------|----------|----------|-------------------|

Source code: https://github.com/mrdulin/mongoose5.x-lab/tree/master/src/stackoverflow/58820254

Answer 2

If you want to create a stub for the post document, which represents an instance of the Post model, you can achieve this by stubbing the Post.prototype.

For example:

server.ts:

import express from 'express';
import Post from './models/post';
import http from 'http';

const app = express();
app.post('/addPost', async (req, res) => {
  const post = new Post(req.body);
  await post.save();
  res.sendStatus(200);
});

const server = http.createServer(app).listen(3000, () => {
  console.info('Http server is listening on http://localhost:3000');
});

export { server };

models/post.ts:

import { model, Schema } from 'mongoose';

const postSchema = new Schema({
  titie: String,
});

export default model('post', postSchema);

server.integration.spec.ts:

import { server } from './server';
import request from 'supertest';
import Post from './models/post';
import sinon from 'sinon';
import { expect } from 'chai';

after((done) => {
  server.close(done);
});

describe('58820254', () => {
  it('/addPost', (done) => {
    const saveStub = sinon.stub(Post.prototype, 'save').returnsThis();
    request(server)
      .post('/addPost')
      .expect(() => {
        console.log('assert');
        expect(saveStub.calledOnce).to.be.true;
      })
      .expect(200, done);
  });
});

Integration test with full coverage:

Http server is listening on http://localhost:3000
  58820254
assert
    ✓ /addPost


  1 passing (25ms)

-----------------------------|----------|----------|----------|----------|-------------------|
File                         |  % Stmts | % Branch |  % Funcs |  % Lines | Uncovered Line #s |
-----------------------------|----------|----------|----------|----------|-------------------|
All files                    |      100 |      100 |      100 |      100 |                   |
 58820254                    |      100 |      100 |      100 |      100 |                   |
  server.integration.spec.ts |      100 |      100 |      100 |      100 |                   |
  server.ts                  |      100 |      100 |      100 |      100 |                   |
 58820254/models             |      100 |      100 |      100 |      100 |                   |
  post.ts                    |      100 |      100 |      100 |      100 |                   |
-----------------------------|----------|----------|----------|----------|-------------------|

Source code: https://github.com/mrdulin/mongoose5.x-lab/tree/master/src/stackoverflow/58820254

Testing the Mongoose save() method by mocking it in an integration test

Answer №1

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