Stubbing nested function calls in sinon

Question

There are three seperate questions that are similar to this one but none of them resembles the case I have.

So I basically have a function which takes a function as a parameter

var myfunc ( func_outer ) {
    return func_outer().func_inner();
}

In my unit tests I want to be able to make a stub of a myfunc2. Basically I need to be able to stub a stub which is a nested stub. I currently use this kind of a manual stub but I would rather do it using sinon stubs if there is a way.

const func_outer = () => {
    return {
       func_inner: () => {return mockResponse;}
    }
};

Has anyone ever faced this situation. Is there an easy way to solve this issue?

Answer 1

From sinon documentation you can check the returns section

stub.returns(obj);
Makes the stub return the provided value.

You can try the following:

First you should make sure that you stub your inner function, and then make it return the value you want.

func_innerStub = sinon.stub().returns('mockResponse')  

Then stub your outer function and make it return the object with your stubbed inner function.

func_outerStub = sinon.stub().returns({func_inner: func_innerStub})

You can follow this pattern with the myfunc function, as well and pass as a param the func_outerStub.