Installing dependencies.

node_modules/eslint-plugin-jest/docs/rules/require-hook.md

@@ -0,0 +1,187 @@
+# Require setup and teardown code to be within a hook (`require-hook`)
+
+Often while writing tests you have some setup work that needs to happen before
+tests run, and you have some finishing work that needs to happen after tests
+run. Jest provides helper functions to handle this.
+
+It's common when writing tests to need to perform setup work that needs to
+happen before tests run, and finishing work after tests run.
+
+Because Jest executes all `describe` handlers in a test file _before_ it
+executes any of the actual tests, it's important to ensure setup and teardown
+work is done inside `before*` and `after*` handlers respectively, rather than
+inside the `describe` blocks.
+
+## Rule details
+
+This rule flags any expression that is either at the toplevel of a test file or
+directly within the body of a `describe`, _except_ for the following:
+
+- `import` statements
+- `const` variables
+- `let` _declarations_, and initializations to `null` or `undefined`
+- Classes
+- Types
+- Calls to the standard Jest globals
+
+This rule flags any function calls within test files that are directly within
+the body of a `describe`, and suggests wrapping them in one of the four
+lifecycle hooks.
+
+Here is a slightly contrived test file showcasing some common cases that would
+be flagged:
+
+```js
+import { database, isCity } from '../database';
+import { Logger } from '../../../src/Logger';
+import { loadCities } from '../api';
+
+jest.mock('../api');
+
+const initializeCityDatabase = () => {
+  database.addCity('Vienna');
+  database.addCity('San Juan');
+  database.addCity('Wellington');
+};
+
+const clearCityDatabase = () => {
+  database.clear();
+};
+
+initializeCityDatabase();
+
+test('that persists cities', () => {
+  expect(database.cities.length).toHaveLength(3);
+});
+
+test('city database has Vienna', () => {
+  expect(isCity('Vienna')).toBeTruthy();
+});
+
+test('city database has San Juan', () => {
+  expect(isCity('San Juan')).toBeTruthy();
+});
+
+describe('when loading cities from the api', () => {
+  let consoleWarnSpy = jest.spyOn(console, 'warn');
+
+  loadCities.mockResolvedValue(['Wellington', 'London']);
+
+  it('does not duplicate cities', async () => {
+    await database.loadCities();
+
+    expect(database.cities).toHaveLength(4);
+  });
+
+  it('logs any duplicates', async () => {
+    await database.loadCities();
+
+    expect(consoleWarnSpy).toHaveBeenCalledWith(
+      'Ignored duplicate cities: Wellington',
+    );
+  });
+});
+
+clearCityDatabase();
+```
+
+Here is the same slightly contrived test file showcasing the same common cases
+but in ways that would be **not** flagged:
+
+```js
+import { database, isCity } from '../database';
+import { Logger } from '../../../src/Logger';
+import { loadCities } from '../api';
+
+jest.mock('../api');
+
+const initializeCityDatabase = () => {
+  database.addCity('Vienna');
+  database.addCity('San Juan');
+  database.addCity('Wellington');
+};
+
+const clearCityDatabase = () => {
+  database.clear();
+};
+
+beforeEach(() => {
+  initializeCityDatabase();
+});
+
+test('that persists cities', () => {
+  expect(database.cities.length).toHaveLength(3);
+});
+
+test('city database has Vienna', () => {
+  expect(isCity('Vienna')).toBeTruthy();
+});
+
+test('city database has San Juan', () => {
+  expect(isCity('San Juan')).toBeTruthy();
+});
+
+describe('when loading cities from the api', () => {
+  let consoleWarnSpy;
+
+  beforeEach(() => {
+    consoleWarnSpy = jest.spyOn(console, 'warn');
+    loadCities.mockResolvedValue(['Wellington', 'London']);
+  });
+
+  it('does not duplicate cities', async () => {
+    await database.loadCities();
+
+    expect(database.cities).toHaveLength(4);
+  });
+
+  it('logs any duplicates', async () => {
+    await database.loadCities();
+
+    expect(consoleWarnSpy).toHaveBeenCalledWith(
+      'Ignored duplicate cities: Wellington',
+    );
+  });
+});
+
+afterEach(() => {
+  clearCityDatabase();
+});
+```
+
+## Options
+
+If there are methods that you want to call outside of hooks and tests, you can
+mark them as allowed using the `allowedFunctionCalls` option.
+
+```json
+{
+  "jest/require-hook": [
+    "error",
+    {
+      "allowedFunctionCalls": ["enableAutoDestroy"]
+    }
+  ]
+}
+```
+
+Examples of **correct** code when using
+`{ "allowedFunctionCalls": ["enableAutoDestroy"] }` option:
+
+```js
+/* eslint jest/require-hook: ["error", { "allowedFunctionCalls": ["enableAutoDestroy"] }] */
+
+import { enableAutoDestroy, mount } from '@vue/test-utils';
+import { initDatabase, tearDownDatabase } from './databaseUtils';
+
+enableAutoDestroy(afterEach);
+
+beforeEach(initDatabase);
+afterEach(tearDownDatabase);
+
+describe('Foo', () => {
+  test('always returns 42', () => {
+    expect(global.getAnswer()).toBe(42);
+  });
+});
+```