jest.js

/**
 * Generates a config for `jest/no-restricted-matchers` that bans all variations
 * of the given base matchers
 *
 * @param {Record<string, string>} matchers
 *
 * @return {Record<string, string>}
 */
const banMatchers = matchers => {
  return Object.fromEntries(
    Object.entries(matchers).flatMap(([matcher, message]) => [
      [matcher, message],
      [`resolves.${matcher}`, message],
      [`resolves.not.${matcher}`, message],
      [`rejects.not.${matcher}`, message],
      [`not.${matcher}`, message]
    ])
  );
};

/**
 * Generates an ESLint config for Jest, based on the Ackama style guide
 *
 * @return {import('eslint').Linter.FlatConfig[]|import('eslint').Linter.LegacyConfig}
 */
const generateConfig = () => {
  /** @type {import('eslint').Linter.RulesRecord} */
  const rules = {
    '@typescript-eslint/unbound-method': 'off',
    'jest/consistent-test-it': 'error',
    'jest/expect-expect': [
      'error',
      // todo: TBD - this will need adjusting for react-testing-library
      { assertFunctionNames: ['expect'] }
    ],
    'jest/no-conditional-expect': 'error',
    'jest/no-conditional-in-test': 'error',
    'jest/no-deprecated-functions': 'error',
    'jest/no-large-snapshots': 'error',
    'jest/no-restricted-matchers': [
      'error',
      banMatchers({
        toThrowErrorMatchingSnapshot:
          'Use `toThrowErrorMatchingInlineSnapshot()` instead',
        toMatchSnapshot: 'Use `toMatchInlineSnapshot()` instead',
        toBeTruthy: 'Avoid `toBeTruthy`',
        toBeFalsy: 'Avoid `toBeFalsy`'
      })
    ],
    'jest/no-test-return-statement': 'error',
    'jest/prefer-called-with': 'error',
    // you can disable this if you use a `beforeEach` setup script,
    'jest/prefer-expect-assertions': 'error',
    'jest/prefer-expect-resolves': 'error',
    'jest/prefer-hooks-on-top': 'error',
    'jest/prefer-lowercase-title': ['error', { ignoreTopLevelDescribe: true }],
    'jest/prefer-spy-on': 'error',
    'jest/prefer-strict-equal': 'error',
    'jest/prefer-todo': 'error',
    'jest/require-hook': 'error',
    'jest/require-to-throw-message': 'error',
    'jest/require-top-level-describe': 'error',
    'jest/unbound-method': 'error',
    'jest/valid-title': 'error',

    'jest/padding-around-after-all-blocks': 'error',
    'jest/padding-around-after-each-blocks': 'error',
    'jest/padding-around-before-all-blocks': 'error',
    'jest/padding-around-before-each-blocks': 'error',
    'jest/padding-around-describe-blocks': 'error',
    'jest/padding-around-test-blocks': 'error'
  };

  if (process.env.ESLINT_USE_FLAT_CONFIG !== 'false') {
    // eslint-disable-next-line n/global-require
    const pluginJest = require('eslint-plugin-jest');

    /** @type {import('eslint').Linter.FlatConfig[]} */
    const config = [
      {
        name: 'ackama/jest',
        ...pluginJest.configs['flat/recommended'],
        plugins: { jest: pluginJest },
        rules: {
          ...pluginJest.configs['flat/recommended'].rules,
          ...pluginJest.configs['flat/style'].rules,
          ...rules
        }
      }
    ];

    return config;
  }

  /** @type {import('eslint').Linter.LegacyConfig} */
  const config = {
    plugins: ['jest'],
    extends: ['plugin:jest/recommended', 'plugin:jest/style'],
    rules
  };

  return config;
};

module.exports = generateConfig();