How do describe blocks and hooks work together?

Hooks are registered inside the currently executing describe. That means a hook declared in an outer block applies to every nested test, and a hook in an inner block applies only there. Jest records the nesting and runs hooks from the outside in on setup, then inside out on teardown.

describe("cart", () => {
  let cart: Cart;

  beforeEach(() => {
    cart = createCart();
  });

  afterEach(() => {
    cart.clear();
  });

  describe("with an item", () => {
    beforeEach(() => {
      cart.add({ sku: "A1", price: 20 });
    });

    test("has a subtotal", () => {
      expect(cart.subtotal()).toBe(20);
    });
  });
});

Hook order for a nested test

• Outer beforeEach runs first
• Inner beforeEach runs next
• The test body runs
• Inner afterEach runs first
• Outer afterEach runs last

Use hooks for setup that every case in the block needs. If only one test needs a value, build it inside that test. Hidden setup is a common source of confusion because a reader sees a bare test body and cannot tell what state already exists.