Simple Mock Function of Passport using Jest - node.js

Question

I am currently unit testing all my routes, including some that are using a custom passport authentication function. I am trying to mock the passport function to test error handling, but I keep getting the error:
TypeError: _passport.default.authenticate(...) is not a function
Here is the actual code that runs in /controllers/users.js:
export const persistentLogin = (req, res, next) => {
// Authenicate the cookie sent on the req object.
passport.authenticate('jwt', { session: false }, async (authErr, user) => {
// If there is an system error, send 500 error
if (authErr) return res.sendStatus(500);
// If no user is returned, send response showing failure.
if (!user) {
return res.status(200).json({
success: 'false',
});
}
})(req, res, next);
};
Here is the testing code in /tests/controllers/users.js:
import passport from 'passport';
import { persistentLogin } from '../../controllers/users';
beforeEach(() => {
mockResponse = () => {
const response = {};
response.status = jest.fn().mockReturnValue(response);
response.json = jest.fn().mockReturnValue(response);
response.sendStatus = jest.fn().mockReturnValue(response);
response.clearCookie = jest.fn().mockReturnValue(response);
response.cookie = jest.fn().mockReturnValue(response);
return response;
};
});
/**
* persistentLogin Tests
*/
describe('Persistent Login Controller', () => {
beforeEach(() => {
req = {};
res = mockResponse();
validateLoginForm.mockClear();
bcrypt.compare.mockClear();
});
// Passport authenication error
test('Should show passport authenication error', async () => {
passport.authenticate = jest.fn((authType, options, callback) => callback('This is an error', null));
await persistentLogin(req, res);
expect(passport.authenticate).toHaveBeenCalledTimes(1);
expect(res.sendStatus).toHaveBeenCalledWith(500);
});
});
If I had to guess, I would say it has something to do with how the (req, res, next) objects are passed into the live function after the fact. But since we are just mocking the function, I am not sure if it actually needs access to those objects.
EDIT #1:
Per the comment from #jakemingolla, I am now thinking it may be because Jest is not running my app.js file which defines my custom JWT strategy.
Here is the code from the /app.js file:
import passport from 'passport';
import passportJWTStrategy from './utils/auth/passport';
app.use(passport.initialize());
passportJWTStrategy(passport);
And the code from the /utils/auth/passport.js file:
import { Strategy } from 'passport-jwt';
/**
* Verifies JWT payload
*
* #param passport The instance of passport module.
*/
export default (passport) => {
const JWTStrategy = Strategy;
// Setup Options Object
const opts = {};
opts.jwtFromRequest = req => req.cookies.jwt;
opts.secretOrKey = process.env.PASSPORT_SECRET;
passport.use(
new JWTStrategy(opts, (jwtPayload, done) => {
if (Date.now() > jwtPayload.expire_date) {
return done('jwt expired');
}
return done(null, jwtPayload);
}),
);
};

Answer 1

You just need a small change:
Your mock for passport.authenticate just needs to return a function:
passport.authenticate = jest.fn((authType, options, callback) => () => { callback('This is an error', null); });

Answer 2

In the question you mock passport.authenticate, but in this case verify function of your strategy is not called. If you want to run this function as well or mock specific strategy then try something like this:
sinon
.stub(passport._strategies.google, 'authenticate')
.callsFake(function verified() {
const self = this;
this._verify(
null,
null,
{
_json: { email: faker.internet.email() },
name: {
givenName: faker.name.firstName(),
familyName: faker.name.lastName(),
},
},
(err, user, info) => {
if (err) {
return self.error(err);
}
if (!user) {
return self.fail(info);
}
return self.success(user, info);
}
);
});
const response = await supertest(app)
.get('/google/callback?code=123');