personObject_spec.js

/*
  You can use any testing suite and assertion library you want.
  I test with mocha & chai
*/
const person = {
  name: 'ken',
  favoriteFood: []
}

function favoriteFood (food) {
  person.favoriteFood.push(food)
}

favoriteFood('apple')
favoriteFood('ramen')

describe('personObject', () => {
  it('it will add food to favoriteFood list', () => {
      expect(person).to.equal({
      name: 'ken',
      favoriteFood: ['apple', 'ramen']
    })
  })
})

// This will pass! :)