basketCalculation.test.ts

describe('Unit | Basket price calculation', () => {
    let basket: Basket
    
    beforeEach(() => basket = new Basket())
    
    it('For an empty basket', () => {
        expect(basket.price).to.equal(0)
    })
    
    describe('Borrowing n different books', () => {
        it('Apply no discount', () => {
            basket.add(new Book('1'))
            basket.add(new Book('2'))
            basket.add(new Book('3'))
            basket.add(new Book('5'))
    
            expect(basket.price).to.equal(32)
        })
    })
    
    describe('Borrowing n times the same book', () => {
        it('Apply no discount for only one book', () => {
            addNTimesTheSameBook(1)
            expect(basket.price).to.equal(8)
        })
        it('Apply 5% discount for two same books', () => {
            addNTimesTheSameBook(2)
            expect(basket.price).to.equal(15.2)
        })
        it('Apply 25% discount for three same books', () => {
            addNTimesTheSameBook(3)
            expect(basket.price).to.equal(18)
        })
        it('Apply 25% discount for more than three times', () => {
            addNTimesTheSameBook(4)
            expect(basket.price).to.equal(24)
        })
        
        function addNTimesTheSameBook(nTimes: number) {
            const book = new Book('1')
            for (let i = 1; i <= nTimes; i++)
                basket.add(book)
        }
    })
})