why the stubbed functions does not works when using destructor with sinon js?

Question

There are a lot of people face the problem of stubing functions with sinon.js doesn't work when using destructorand there is a great explantion mentioned on Sinon stub function used with destructuring. And as mentioned in the answer, when using the destructor we call always the original function:

const stub = (o, method) => (o[method] = () => "I am a stub");

const obj = {
  methodFoo() {
    return "I am foo";
  }
};

// same as doing `const methodFoo = obj.methodFoo;`
const { methodFoo } = obj; // "import" using destructuring

console.log("obj.methodFoo(): ", obj.methodFoo());
console.log("methodFoo()", methodFoo());

console.log("Stubbing out method!");
stub(obj, "methodFoo");

console.log("obj.methodFoo: ", obj.methodFoo());
console.log("methodFoo()", methodFoo());

I searched for an answer why the destructor overrides the stub or how it works under the hood to understand how to manipulate data but I didn't get any solution. Is there any details about this issue ?

Answer 1

Stubbing overrides the methods property. If you take this contrived example:

 const obj = { prop: "value" };

 const prop = obj.prop; // or { prop } = obj;

 obj.prop = "new value"; // stub()

 console.log(prop); // "value"

then it might become clearer. Think of methods as values that can be copied (actually a reference to them gets copied).