jest/require-hook

Code at the top level of a test file, or directly in the body of a describe, runs once while Jest collects the tests. It runs even if every test in that block is skipped, and the state it builds is shared by all tests, so one test can break the next. Put it in beforeAll, beforeEach, afterEach or afterAll.

The rule reports two things in those places:

• a statement that's only a function call, such as setup();
• a let or var that starts with a value other than null or undefined

const declarations are allowed. So are calls to describe, test, it and the hooks, and calls on jest, such as jest.mock().

The rule checks every file it's turned on for, not only tests. Turn it on for your test files only.

Configure

Off by default. To turn it on:

[lint.rules]
"jest/require-hook" = "error" # or "warn"

Every option, set to its default:

[lint.rules]
"jest/require-hook" = ["error", {
  allowedFunctionCalls = [], # list of strings
}]

Examples

Reported:

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

let db = connect();
db.seed(["ada", "grace"]);

describe("users", () => {
  clearCache();

  test("finds a user", () => {
    expect(db.find("ada")).toBeDefined();
  });
});

Not reported:

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

jest.mock("./mailer");

const names = ["ada", "grace"];
let db;

beforeAll(() => {
  db = connect();
  db.seed(names);
});

describe("users", () => {
  beforeEach(() => {
    clearCache();
  });

  test("finds a user", () => {
    expect(db.find("ada")).toBeDefined();
  });
});

Options

expect.extend() and the short forms fit, xit, xtest, fdescribe and xdescribe are reported unless you list them:

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

expect.extend({ toBeUser });

xtest("finds a user", () => {
  expect(db.find("ada")).toBeUser();
});

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

expect.extend({ toBeUser });

xtest("finds a user", () => {
  expect(db.find("ada")).toBeUser();
});