How to mock functions when testing with jest and superagent - node.js

Question

I have run into an issue that files and functions cannot be mocked, that is used in a handler of an API call. This call is simulated using superagent.
Here is the code of the test
// users.itest.js
const request = require('superagent');
const get = async url => request
.get(`${process.env.API_URL}${url}`);
describe('endpoint', () => {
it('GET', async () => {
jest.mock('../token-store', () => ({
getToken: jest.fn().mockReturnValue('token'),
}));
const { status, body } = await get('/api/users');
expect(status).toEqual(200);
expect(body).toHaveValidSchema(userSchema);
});
And here is the handler that is called by the '/api/users' endpoint
const someHandler = async (req, res) => {
const token = await tokenStore.getToken();
res.send(token);
};
I tried mocking it like shown, however, I couldn't find a solution.
Thanks.

Answer 1

You should use jest.mock() in the module scope, not function scope.
Here is the integration test solution:
app.js:
const express = require('express');
const tokenStore = require('./token-store');
const app = express();
const someHandler = async (req, res) => {
const token = await tokenStore.getToken();
res.send(token);
};
app.get('/api/users', someHandler);
module.exports = app;
token-store.js:
async function getToken() {
return 'real token';
}
module.exports = {
getToken,
};
users.test.js:
const request = require('superagent');
const app = require('./app');
const port = 3000;
process.env.API_URL = `http://localhost:${port}`;
const get = async (url) => request.get(`${process.env.API_URL}${url}`);
jest.mock('./token-store', () => ({
getToken: jest.fn().mockReturnValue('token'),
}));
describe('endpoint', () => {
let server;
beforeAll((done) => {
server = app.listen(port, () => {
console.info(`HTTP server is listening on http://localhost:${server.address().port}`);
done();
});
});
afterAll((done) => {
server.close(done);
});
it('GET', async () => {
const { status, text } = await get('/api/users');
expect(status).toEqual(200);
expect(text).toBe('token');
});
});
Integration test result with coverage report:
PASS src/stackoverflow/59426030/users.test.js (10.767s)
endpoint
✓ GET (74ms)
console.info src/stackoverflow/59426030/users.test.js:16
HTTP server is listening on http://localhost:3000
----------|----------|----------|----------|----------|-------------------|
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s |
----------|----------|----------|----------|----------|-------------------|
All files | 100 | 100 | 100 | 100 | |
app.js | 100 | 100 | 100 | 100 | |
----------|----------|----------|----------|----------|-------------------|
Test Suites: 1 passed, 1 total
Tests: 1 passed, 1 total
Snapshots: 0 total
Time: 12.254s
Source code: https://github.com/mrdulin/jest-codelab/tree/master/src/stackoverflow/59426030