sinon依赖函数伪造

Question

I want to fake or stub a function which is not used as a method of an object.See mylib.js

//multiplicaiton.js

module.exports = function(x,y) {
  return x*y;
}

//mylib.js

let Multiplication = require('./multiplication');

let myLib = function(x,y) {
  var result = Multiplication(x,y)
  return result
}

module.exports = myLib;

//test.js

let sinon = require('sinon');
let mylib = require('./mylib');
let chai = require('chai');
let expect = chai.expect;

describe('My Test', function() {

   it('Faking Globally',function() {
     //How do I declare 'multiplication' as Globally and fake it.
     expect(mylib(2,3)).to.deep.equal(6);
   })

})

Answer 1

If you want to globally replace a module you need to use a link seam , which basically injects a different module (for instance a Sinon spy) instead of the real one. You can see a whole how-to in the Sinon documentation .

For your case it would be something like

const proxyquire = require('proxyquire');
const sinon = require('sinon');
const chai = require('chai');
const expect = chai.expect;

// replace the dependency with a stub
const multiplicationFake = sinon.fake.returns(42);
const mylib = proxyquire('./mylib', { './multiplication': multiplicationFake });

describe('My Test', function() {

   it('Faking Globally',function() {
     const result = mylib(2,3);
     expect(multiplicationFake.calledOnce).to.equal(true);
     expect(result).to.deep.equal(42);
   })   
})

I used Sinon fakes here, but you can use spies or stubs if you prefer them.