Jest Express testing middleware with arguments

Question

I'm pretty new to node and this is my first time unit testing an app. I'm doing well with Jest faking the request with Jest function as below

// Create a fake request
 const mockRequest = (sessionData, body) => ({
  session: { data: sessionData },
  body
});

// Create a fake response
 const mockResponse = () => {
  const res = {};
  res.status = jest.fn().mockReturnValue(res);
  res.json = jest.fn().mockReturnValue(res);
  return res;
};

const mockNext = () => {
  const next = jest.fn();
  return next;
};

So I can use them like follows

doSomething(req, res, next);
expect(res.status).toHaveBeenCalledWith(201);
//or
expect(next).toHaveBeenCalled();

That's enough for all the cases until I found that my authorisation middleware includes a couple of parameters so I can not pass the fake res and req as below

exports.isAllowedTo = (par1, par2) => {
    return async (req, res, next) => {
        try {
            //
            // Grant logic here that needs par1 and par2
            //

            if(granted)
                next();
            else
                return res.status(401).json({
                    error: "You don't have enough permission to perform this action"
                });

        } catch (err) {
            res.status(406).json({
                error: err.toString(),
            })
        }
    }
}

If I test isAllowTo(req, res, next) with the mock req, res and next then I'm missing the 2 parameters needed by the function. Actually when I do this, the function isAllowTo() is not even called. I don't know how to deal with that. Any suggestion or approach?

score 3 · Accepted Answer · answered Apr 15 '20 at 02:20

Two months later I realized that the real problem is that I'm testing a function inside of another function. So firstly I store the function in a variable so I can test it as a regular middleware.

test('Grant access if user role is allowed to', async () => {

    const isAllowToTester = userController.isAllowedTo(par1, par2);

    await isAllowToTester(req, res, next)

    expect(next).toHaveBeenCalled();

});

Hope this helps someone else. Credits to this post

score 0 · Answer 2 · answered Jan 31 '20 at 15:47

0

Check out https://github.com/nock/nock it's a library dedicated to mocking requests and responses, it's really easy to use with unit tests/jest. I personally don't think is worth it to write your own mocking implementation.

answered Jan 31 '20 at 15:47

noone

21
3

Thank you! Looks pretty useful mocking. AFAICS Nock calls the endpoint but I want to test unit by unit. The piece of code above is a middleware that I isolated in order to test it. – Nathan Lo Sabe Jan 31 '20 at 16:24
1

Hmm, I see, I think sinon's stubs could help you do that: https://sinonjs.org/releases/latest/stubs/ take a look. – noone Jan 31 '20 at 17:19

Jest Express testing middleware with arguments

2 Answers2

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