node.js - How to test javascript function independently with mocha chai and sinon? -

i new unit testing , have been reading few tutorials practice javascript. use silly example explain problem.

let's john needs go school , before knowing if he's ready go has check if has bag , headphones. called following function:

john.isreadytogo; 

the implementation of isreadttogo() function character object follows:

characher.isreadytogo = function() {     return this.hasbag() && this.hasheadphones(); }  characher.hasbag = function() {     // return true or false }  characher.hasheadphones = function() {     //return true or false } 

now, let's want test function. in unit testing recommended test functions without them being affected other functions. means in case have test 3 functions character.isreadytogo() function need have mock values this.hasbag() , this.hasheadphones(). right?

if so, give me hint on how can mock these 2 values?

here's example:

let character = {};  character.isreadytogo = function() {     return this.hasbag() && this.hasheadphones(); }  character.hasbag = function() {     // return true or false }  character.hasheadphones = function() {     //return true or false }  const sinon  = require('sinon'); const expect = require('chai').expect;  describe('is character ready?', () => {    beforeeach(() => {     sinon.stub(character, 'hasbag');     sinon.stub(character, 'hasheadphones');   });    aftereach(() => {     character.hasbag.restore();     character.hasheadphones.restore();   });    it("not if don't have bag or headphones", () => {     character.hasbag.returns(false);     character.hasheadphones.returns(false);     expect(character.isreadytogo()).to.be.false;   });    it("not if have headphones no bag", () => {     character.hasbag.returns(false);     character.hasheadphones.returns(true);     expect(character.isreadytogo()).to.be.false;   });    it("not if have bag no headphones", () => {     character.hasbag.returns(true);     character.hasheadphones.returns(false);     expect(character.isreadytogo()).to.be.false;   });    it("yes, if have bag , headphones", () => {     character.hasbag.returns(true);     character.hasheadphones.returns(true);     expect(character.isreadytogo()).to.be.true;   });  }); 

for each test, stubs character.hasbag , character.hadheadphones (this done in beforeeach). replaces original new function (the stub) can control.

depending on test, stub "told" return each function (using .returns()), isreadytogo called, , result checked against expectation.

after each test, stub restored (meaning original function restored).