I want to mock some object of some Class, but catch this err:

```
function MyClass(){}

var myInstance = new MyClass();
var mock = sinon.mock(myInstance);

console.log(mock instanceof MyClass); // false

```

How can I pass this mock to the unit under the test, if unit checks exactly the same instanceof in a constructor?

I know, that stub solving this problem, but I need exactly Mock.

Thanks =)