instanceof doesn't seem to work with class mocks

[Philipp3211]

In our tests we want to mock classes. When mocking them with the createMock function, the instanceof operator is not returning true when checking for the to be mocked class:

class Person {
    name: string;
}
const myPerson = createMock<Person>();

const isOfType = myPerson instanceof Person; // is false

I'm not sure if this is a bug or not, but it prevents us from using the mock as a direct substitute, because our code depends on the instanceof operator returning true.

Workaround is possible by using Object.setPrototypeOf(myPerson, Person.prototype);.