Edit in JSFiddle

describe('Product', function () {
    var product;
    beforeEach(function () {
        product = new Product({name: 'foo'});
    });
    describe('.getName()', function () {
        it('returns name formatted using format function', function () {
            var formatFunctionStub = function (productName) { return productName + '-bar'; }
 
            expect(product.getName(formatFunctionStub)).toEqual('foo-bar');
        });
    });
});