describe('Add and subtract', () => {

    it('Should contain add, subtract, get', () => {

        let returnValue = createCalculator();

        expect(returnValue).to.haveOwnProperty('add');

        expect(returnValue).to.haveOwnProperty('subtract');

        expect(returnValue).to.haveOwnProperty('get');

    });


    it('Should not take any parameters', () => {

        let obj = createCalculator();

        obj.add(5);

        obj.add(5);

        let returnValue = obj.get();

        expect(returnValue).to.equal(10);

    });


    it('Should be a number', () => {

        let obj = createCalculator();

        obj.add('sss');

        obj.subtract('dssa');

        let returnValue = obj.get();

        expect(returnValue).to.be.NaN;

    });


    it('Should return the variable value', () => {

        expect(createCalculator().get()).to.equal(0);

    });



});