使用Sinon.JS模擬JavaScript構造函數

Question

我想對下面的ES6類進行單元測試：

// service.js
const InternalService = require('internal-service');

class Service {
  constructor(args) {
    this.internalService = new InternalService(args);
  }

  getData(args) {   
    let events = this.internalService.getEvents(args);
    let data = getDataFromEvents(events);
    return data;
  }
}

function getDataFromEvents(events) {...}

module.exports = Service;

如何使用Sinon.JS模擬構造函數以模擬internalService getEvents來測試getData ？

我查看了使用Sinon的Javascript：Mocking Constructor，但無法提取解決方案。

// test.js
const chai = require('chai');
const sinon = require('sinon');
const should = chai.should();

let Service = require('service');

describe('Service', function() {
  it('getData', function() {
    // throws: TypeError: Attempted to wrap undefined property Service as function
    sinon.stub(Service, 'Service').returns(0);
  });
});

Answer 1

您可以使用sinon.createStubInstance創建命名空間或創建存根實例（這不會調用構造函數）。

創建命名空間：

const namespace = {
  Service: require('./service')
};

describe('Service', function() {
  it('getData', function() {
    sinon.stub(namespace, 'Service').returns(0);
    console.log(new namespace.Service()); // Service {}
  });
});

創建存根實例：

let Service = require('./service');

describe('Service', function() {
  it('getData', function() {
    let stub = sinon.createStubInstance(Service);
    console.log(stub); // Service {}
  });
});