usage of sinon.js

test.js

TestCase("usage.sinon", {
    'test mock for constructor': sinon.test(function() {

        var obj = {
            hoge: function(id) {
                this.id = id
            }
        };

        this.mock(obj)
        .expects("hoge")
        .withArgs(2)
        //.returns(new obj.hoge(2));    //cause expectation error.
        .returns(Object.create(obj.hoge.prototype, {id: {value: 2}}));//spy

        assertEquals(2, new obj.hoge(2).id);

    })
});