Express router's mock post handler doesn't work as expected - express

Question

I have a documents router which has router.post('/mine', [auth, uploadFile], async (req, res) => { ... }) route handler. The actual implementation of this route handler is below.
documents.js router
const createError = require('./../helpers/createError');
const auth = require('./../middlewares/auth');
const uploadFile = require('./../middlewares/uploadFile');
const express = require('express');
const router = express.Router();
router.post('/mine', [auth, uploadFile], async (req, res) => {
try {
let user = await User.findById(req.user._id);
let leftDiskSpace = await user.leftDiskSpace();
if(leftDiskSpace < 0) {
await accessAndRemoveFile(req.file.path);
res.status(403).send(createError('Your plan\'s disk space is exceeded.', 403));
} else {
let document = new Document({
filename: req.file.filename,
path: `/uploads/${req.user.username}/${req.file.filename}`,
size: req.file.size
});
document = await document.save();
user.documents.push(document._id);
user = await user.save();
res.send(document);
}
} catch(ex) {
res.status(500).send(createError(ex.message, 500));
}
});
module.exports = router;
I'm currently writing integration tests using Jest and Supertest. My current documents.test.js test file is below:
documents.test.js test file
const request = require('supertest');
const { Document } = require('../../../models/document');
const { User } = require('../../../models/user');
const fs = require('fs');
const path = require('path');
let server;
describe('/api/documents', () => {
beforeEach(() => { server = require('../../../bin/www'); });
afterEach(async () => {
let pathToTestFolder = path.join(process.cwd(), config.get('diskStorage.destination'), 'user');
// Remove test uploads folder for next tests
await fs.promises.access(pathToTestFolder)
.then(() => fs.promises.rm(pathToTestFolder, { recursive: true }))
.catch((err) => { return; });
// Remove all users and documents written in test database
await User.deleteMany({});
await Document.deleteMany({});
server.close();
});
describe('POST /mine', () => {
it('should call user.leftDiskSpace method once', async () => {
let user = new User({
username: 'user',
password: '1234'
});
user = await user.save();
let token = user.generateAuthToken();
let file = path.join(process.cwd(), 'tests', 'integration', 'files', 'test.json');
let documentsRouter = require('../../../routes/documents');
let errorToThrow = new Error('An error occured...');
user.leftDiskSpace = jest.fn().mockRejectedValue(errorToThrow);
let mockReq = { user: user };
let mockRes = {};
documentsRouter.post = jest.fn();
documentsRouter.post.mockImplementation((path, callback) => {
if(path === '/mine') {
console.warn('called');
callback(mockReq, mockRes);
}
});
const res = await request(server)
.post('/api/documents/mine')
.set('x-auth-token', token)
.attach('document', file);
expect(documentsRouter.post).toHaveBeenCalled();
expect(user.leftDiskSpace).toHaveBeenCalled();
});
});
});
I create mock post router handler for documents.js router. As you can see from mockImplementation for this route handler, it checks if the path is equal to '/mine' (which is my supertest endpoint), then calls console.warn('called'); and callback. When I run this test file, I can not see any yellow warning message with body 'called'. And also when POST request endpoint /api/documents/mine the server doesn't trigger my mock function documentsRouter.post. It has never been called. So I think the server's documents router is not getting replaced with my mock post route handler. It still uses original post route handler to respond my POST request. What should I do to test if my mock documentsRouter.post function have been called?
Note that my User model has a custom method for checking left disk space of user. I also tried to mock that mongoose custom method but It also doesn't work.