Sinon spy on console.log call not registered

Question

I'm trying to learn about Sinon and want to spy on console.log. The code is simple:

function logToConsole() {
    console.log('Hello World');
}

exports.logToConsole = logToConsole;

But if I want to test it, it doesn't work because the call to console.log is not registered inside the 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 I execute console.log inside the test itself, it is captured and 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, it doesn't seem to be able to spy on inner-function calls at all. Is this not the purpose of a spying library?

e.g.

function a() {};

function b() {
    a();
}

Answer 1

It looks like you're not actually using sinon-chai, the code you post is missing this line:

chai.use(sinonChai);

EDIT: here is the code I 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 to console', function() {
      sut.logToConsole();
      expect(console.log).to.be.called;
    });
  });

  describe('logToConsole2', function() {
    it('should not log to 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() {
};