Edit in JSFiddle

var productBasket = function (products) {
    return {
        total: function () {
            return 0;
        }
    }
};
 
describe('Product basket', function () {
    describe('#total()', function () {
        it('returns 0 when basket is empty', function () {
            expect(productBasket([]).total()).toEqual(0);
        });
    })
});