Good mocha test

good-mocha-test.js

//describe what are you testing: given
describe('button widget', function(){
  //describe the aspect of object that you are testing: when
  describe('when button is clicked', function(){
    //verify the expectation: then
    it('onClickHandler should be called ', function(){
      expect(onClickHandler).to.have.been.called
    })
  })
});