In Jasmine Test string __proto__ doesn't equal String.prototype

Question

If I have the test like so, which should pass expect("test".__proto__ === String.prototype).toBe(true) it fails with the error Expected false to be true.

The reason I'm testing this is because in my code jquery extensions adds format to String.prototype. However, when I go todo my test "my test {0}".format(1) I get "undefined is not a function", and looking closer all string in a Jasmine test dont have the String.prototype as their prototype.

---EDIT--- After further testing I found that if I have:

it("test string prototype", function() {
   var test_string = "test"
   expect(test_string.__proto__ === String.prototype).toBe(true)
   with (frameContext) {
      expect(test_string.__proto__ === String.prototype).toBe(true)
   }
});

the first expect passes but the second doesn't.

---EDIT---

expect(typeof String.prototype.format !== "undefined").toBe(true)
expect(test_string.__proto__ === String.prototype).toBe(true)
with (frameContext) {
    expect(typeof String.prototype.format !== "undefined").toBe(true)
    expect(test_string.__proto__ === String.prototype).toBe(true)
}

first expect fails, second expect passes

within the with, first expect pass, and second fails.