javascript - Sinon spy on console.log call not registered -

i'm trying learn sinon , want spy on console.log. code simple:

function logtoconsole() {     console.log('hello world'); }  exports.logtoconsole = logtoconsole; 

but if want test it, doesn't work because call console.log not registered inside system under test:

var chai = require('chai'),     expect = chai.expect,     sinonchai = require('sinon-chai'),     sinon = require('sinon'),     sut = require('../src/logtoconsole');  chai.use(sinonchai);  describe('logtoconsole', function() {     it('should spy on console.log', function() {         sinon.spy(console, 'log');          sut.logtoconsole();          expect(console.log).to.have.been.called;     }); }); 

however if execute console.log inside test itself, captured , passes:

it('should spy on console.log', function() {     sinon.spy(console, 'log');      sut.logtoconsole();     console.log('test');      expect(console.log).to.have.been.called; }); 

interestingly, doesn't seem able spy on inner-function calls @ all. not purpose of spying library?

e.g.

function a() {};  function b() {     a(); } 

it looks you're not using sinon-chai, code post missing line:

chai.use(sinonchai); 

edit: here code tested with:

// test.js var chai = require('chai'),     expect = chai.expect,     sinonchai = require('sinon-chai'),     sinon = require('sinon'),     sut = require('./log');  chai.use(sinonchai);  describe('logging', function() {    beforeeach(function() {     sinon.spy(console, 'log');   });    aftereach(function() {     console.log.restore();   });    describe('logtoconsole', function() {     it('should log console', function() {       sut.logtoconsole();       expect(console.log).to.be.called;     });   });    describe('logtoconsole2', function() {     it('should not log console', function() {       sut.logtoconsole2();       expect(console.log).to.not.be.called;     });   }); });  // log.js module.exports.logtoconsole = function() {   console.log('hello world'); };  module.exports.logtoconsole2 = function() { };