Testing throw error inside generator?

Question

I am trying to test the thrown of an error inside a generator function as follow, using Jest and Chai:

    // function

    function * gen () {
        yield put({ type: TIME_OUT_LOGOUT })
        throw new Error('User has logged out')
    }

    //test

    let genFunc = gen()

    expect(genFunc().next).to.deep.equal(put({ type: TIME_OUT_LOGOUT }))

    expect(genFunc().next).to.throw(Error('User has logged out'));

But it isn't working. Which would be the correct way to test this?

Answer 1

Try changing your testing code from genFunc().next to genFunc.next().value

---

EDIT:

The assertions should be:

expect(genFunc.next().value).toEqual(put({type: TIME_OUT_LOGOUT})); expect(genFunc.next).toThrow(Error);

For the second assertion expect(() => genFunc.next()).toThrow(Error); would also work, but the wrapper function () => genFunc.next() is unnecessary since genFunc.next does not take any parameters.