CODEWITHSUNDEEP
mockingjestjs
Julian Torregrosa
Julian Torregrosa

Reputation: 861

jest - spy function inside mock function

I have a chained mock function inside another mock function, I need to spy both of them but I don't know how to spy the second one.

This is an example:

res = {
  status: jest.fn(() => {
    return {
      json: jest.fn()
    }
  })
}

expect(res.status).toBeCalled() // This works
expect(res.status.json).toBeCalled() // This does not
expect(res.status().json).toBeCalled() // This does neither

Upvotes: 0

Views: 750

Answers (2)

IceManSpy
IceManSpy

Reputation: 1098

Now you can use https://jestjs.io/docs/en/mock-function-api#mockfnmockreturnthis

Like this:

const res = {
  status: jest.fn().mockReturnThis(),
  send: jest.fn()
};

// call function and pass res

expect(res.status).toHaveBeenCalledTimes(1);
expect(res.status).toHaveBeenCalledWith(200);
expect(res.send).toHaveBeenCalledTimes(1);
expect(res.send).toHaveBeenCalledWith("Something");

In app:

res.status(200).send("Something");

Upvotes: 2

Julian Torregrosa
Julian Torregrosa

Reputation: 861

I found the solution here: Spying on chained method calls with Jest not working

The trick is to separate definitions:

json = { json: jest.fn() }
res = {
  status: jest.fn(() => json)
}

Upvotes: 2

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