Unit test bluebird Promise.all with Mocha/Chai - node.js

Question

What would be the proper way to unit test this getall function using mocha/chai? I'm having a hard time understanding what to expect with Promise.all.
const Promise = require('bluebird');
const someApiService = require('./someapiservice');
const _ = require('underscore');
function getall(arr) {
let promises = _.map(arr, function(item) {
return someApiService(item.id);
});
return Promise.all(promises);
}

Answer 1

We should stub standalone function someApiService use link seams. This is the CommonJS version, so we will be using proxyquire to construct our seams. Additionally, I use sinon.js to create the stub for it.
E.g.
getall.js:
const Promise = require('bluebird');
const someApiService = require('./someapiservice');
const _ = require('underscore');
function getall(arr) {
let promises = _.map(arr, function (item) {
return someApiService(item.id);
});
return Promise.all(promises);
}
module.exports = getall;
someapiservice.js:
module.exports = function someApiService(id) {
return Promise.resolve('real data');
};
getall.test.js:
const proxyquire = require('proxyquire');
const sinon = require('sinon');
const { expect } = require('chai');
describe('45337461', () => {
it('should pass', async () => {
const someapiserviceStub = sinon.stub().callsFake((id) => {
return Promise.resolve(`fake data with id: ${id}`);
});
const getall = proxyquire('./getall', {
'./someapiservice': someapiserviceStub,
});
const actual = await getall([{ id: 1 }, { id: 2 }, { id: 3 }]);
expect(actual).to.deep.equal(['fake data with id: 1', 'fake data with id: 2', 'fake data with id: 3']);
sinon.assert.calledThrice(someapiserviceStub);
});
});
unit test result:
45337461
✓ should pass (2745ms)
1 passing (3s)
-------------------|---------|----------|---------|---------|-------------------
File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s
-------------------|---------|----------|---------|---------|-------------------
All files | 88.89 | 100 | 66.67 | 88.89 |
getall.js | 100 | 100 | 100 | 100 |
someapiservice.js | 50 | 100 | 0 | 50 | 2
-------------------|---------|----------|---------|---------|-------------------