07. Add / Subtract

describe('It should return module(object)', () => {
    it('Return object', () => {
        expect(typeof createCalculator()).to.equal('object');
    });

    it('Contains add property', () => {
        expect(createCalculator()).to.have.property('add');
    });

    it('Contains subtract property', () => {
        expect(createCalculator()).to.have.property('subtract');
    });

    it('Contains get property', () => {
        expect(createCalculator()).to.have.property('get');
    });

    it('Return a function', () => {
        expect(typeof createCalculator().add).to.equal('function');
    });

    it('Return a function', () => {
        expect(typeof createCalculator().subtract).to.equal('function');
    });

    it('Return a function', () => {
        expect(typeof createCalculator().get).to.equal('function');
    });

    let calc = createCalculator();

    it('Add to parse string number', () => {
        calc.add('1');
        expect(calc.get()).to.equal(1);
    });

    it('Subtract to parse string number', () => {
        calc.subtract('2');
        expect(calc.get()).to.equal(-1);
    });

    it('Add a number', () => {
        calc.add(2);
        expect(calc.get()).to.equal(1);
    });

    it('Subtract a number', () => {
        calc.subtract(2);
        expect(calc.get()).to.equal(-1);
    });

    it('Add a number', () => {
        calc.add(2);
        expect(calc.get()).to.equal(1);
    });

    it('Return the value', () => {
        expect(typeof calc.get()).to.equal('number');
        expect(calc.get()).to.equal(1);
    });

    it('String params to return NaN', () => {
        let calc = createCalculator();
        calc.add('string');
        expect(calc.get()).to.be.NaN;
    })
});