jest/no-hooks

A hook usually sets a variable that every test in the block shares. To understand one test, you have to find the hooks above it, and a test that changes the shared value can break the next one. A test that calls a setup function itself shows everything it depends on.

Configure

Off by default. To turn it on:

[lint.rules]
"jest/no-hooks" = "error" # or "warn"

Every option, set to its default:

[lint.rules]
"jest/no-hooks" = ["error", {
  allow = [], # list of strings
}]

Examples

Reported:

import { beforeEach, expect, test } from "@jest/globals";

let cart;

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

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

Not reported:

import { expect, test } from "@jest/globals";

test("starts empty", () => {
  const cart = createCart();
  expect(cart.items).toEqual([]);
});

Options

Option	Default	What it does
allow	[]	Names of hooks to allow.

With { "allow": ["afterEach"] }, only beforeAll is reported here:

import { afterEach, beforeAll, jest } from "@jest/globals";

afterEach(() => {
  jest.restoreAllMocks();
});

beforeAll(() => {
  server.listen();
});

When not to use it

Hooks are the usual way to start something slow once per file, such as a server or a database, and to stop it afterwards. If your tests do that, allow those hooks or leave the rule off.