Challenge 2: Proving beforeEach Actually Resets State — Possible Solution
====================================================================

let cart;

beforeEach(() => {
  cart = [];
});

describe("cart", () => {
  it("starts empty", () => {
    expect(cart).toEqual([]);
  });

  it("has length 1 after adding one item", () => {
    cart.push("apple");
    expect(cart.length).toBe(1);
  });

  it("is empty again in a fresh test, even after the previous test added an item", () => {
    expect(cart).toEqual([]);
  });
});

WHY THIS WORKS AS AN ANSWER
------------------------------
cart is declared outside beforeEach (with let, not const) so the same
variable can be reassigned before each test, rather than redeclared —
beforeEach resets it to an empty array before EVERY test in the
describe block runs, exactly as this chapter described.

The second test pushes an item and checks cart.length === 1 — proving
adding an item works as expected, using toBe since length is a
primitive number.

The THIRD test is what actually proves the reset works, not just the
comment claiming it does: if beforeEach were NOT running between tests
(say, it only ran once via a beforeAll instead), this third test would
see the "apple" item still sitting in cart from the second test, and
expect(cart).toEqual([]) would FAIL. Since this test passes, it
demonstrates concretely that beforeEach really does reset cart before
every single test, not just once at the start of the suite — directly
verifying the isolation guarantee this chapter's Setup and Teardown
section described, rather than just taking it on faith.