Stub chained promises with sinon

Question

  let image = await object
      .firstCall(params)
      .promise()
      .then(data => {
        return data
      })
      .catch(err => {
        console.(err)
      });

What's the way to stub the chained promises with sinon ? I've tried the following, but with no luck

promiseStub = sinon.stub().callsArg(0).resolves("something");
firtCallStub = sinon.stub(object, "firstCall").returns(this.promiseStub);

Answer 1

Unit test solution:

index.ts :

import { object } from './obj';

export async function main() {
  const params = {};
  return object
    .firstCall(params)
    .promise()
    .then((data) => {
      return data;
    })
    .catch((err) => {
      console.log(err);
    });
}

obj.ts :

export const object = {
  firstCall(params) {
    return this;
  },
  async promise() {
    return 'real data';
  },
};

index.test.ts :

import { main } from './';
import { object } from './obj';
import sinon from 'sinon';
import { expect } from 'chai';

describe('64795845', () => {
  afterEach(() => {
    sinon.restore();
  });
  it('should return data', async () => {
    const promiseStub = sinon.stub(object, 'promise').resolves('fake data');
    const firtCallStub = sinon.stub(object, 'firstCall').returnsThis();
    const actual = await main();
    expect(actual).to.be.equal('fake data');
    sinon.assert.calledWithExactly(firtCallStub, {});
    sinon.assert.calledOnce(promiseStub);
  });
});

unit test result:

  64795845
    ✓ should return data


  1 passing (32ms)

----------|---------|----------|---------|---------|-------------------
File      | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s 
----------|---------|----------|---------|---------|-------------------
All files |   66.67 |      100 |      40 |   66.67 |                   
 index.ts |   83.33 |      100 |   66.67 |   83.33 | 12                
 obj.ts   |   33.33 |      100 |       0 |   33.33 | 3-6               
----------|---------|----------|---------|---------|-------------------