为什么 sinon 存根返回未定义？

Question

I am trying to stub a library function with Sinon. Sorry can't post exact code but it looks something like the code below.

The library I am trying to stub library.js

async function a(input) {
    // make some api calls here
    returns input;
}
export async function b {
    const output = await a(123);
    // do some magic here with output
    // call again a
    returns a(output);
}

My test case file: sinon.js

import * as lib from 'library.js'

describe('', ()=>{
    it('', ()=>{
        sinon.stub(lib, 'b')
        .withArgs(123)
        .resolves(123)
    })
})

when I run this code my stub returns undefined instead of expected output which 123 Can anyone help me find what's wrong I am doing here?

Answer 1

I do not claim to be an expert on this subject but it seems to me you are trying to stub instead of mock. Try something like this.

describe('', () => {
  it('', () => {
    const mock = sinon.mock(lib);
    mock
      .expects('b').withArgs(123)
      .resolves(345);
    lib.b(123).then((c) => console.log(c));
  })
})

This will print 345. Pretty sure there is a more elegant way but this will work.