Angular >=13

Angular 13 introduces ESM package format for Angular packages. jest-preset-angular currently supports testing with Jest in CommonJS mode with Angular 13 using default preset.

important

With Jest 28 and jest-preset-angular v12.0.0, ng-jest-resolver is no longer required to have in Jest config. This resolver is also excluded from our default and default ESM presets.

Starting from v11.0.0, jest-preset-angular introduces a few extra changes to be able to run Jest with Angular 13:

• moduleFileExtensions is updated to include mjs files as accepted module format.

• transformIgnorePatterns is added to inform Jest to transform .mjs files.

• transform is updated to include .mjs extension to transform to CommonJS codes.

Migration steps from Angular < 13

• Upgrade the project to Angular 13 following guide

• If one is using the default preset as following:

JavaScript

// jest.config.js
module.exports = {
  preset: 'jest-preset-angular',
};

TypeScript

// jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  preset: 'jest-preset-angular',
};

export default jestConfig;

there are no migration steps required

Using ES Modules

ES Modules support is new and may encounter issues. See example-app-v13 for an example with tests that run using ESM, and using ESM + isolated.

Your jest.config.js should be changed to something like:

JavaScript

// jest.config.js
const { pathsToModuleNameMapper } = require('ts-jest/utils');
const { paths } = require('./tsconfig.json').compilerOptions;

/** @type {import('ts-jest/dist/types').JestConfigWithTsJest} */
module.exports = {
  preset: 'jest-preset-angular/presets/defaults-esm',
  transform: {
    '^.+\\.(ts|js|html|svg)$': [
      'jest-preset-angular',
      {
        tsconfig: '<rootDir>/tsconfig-esm.spec.json',
        stringifyContentPathRegex: '\\.(html|svg)$',
        isolatedModules: true,
        useESM: true,
      },
    ],
  },
  moduleNameMapper: {
    ...pathsToModuleNameMapper(paths, { prefix: '<rootDir>' }),
    tslib: 'tslib/tslib.es6.js',
  },
  setupFilesAfterEnv: ['<rootDir>/setup-jest.ts'],
};

TypeScript

// jest.config.ts
import type { Config } from 'jest';
import { pathsToModuleNameMapper } from 'ts-jest';
import { compilerOptions } from './tsconfig.json';

const jestConfig: Config = {
  preset: 'jest-preset-angular/presets/defaults-esm',
  transform: {
    '^.+\\.(ts|js|html|svg)$': [
      'jest-preset-angular',
      {
        tsconfig: '<rootDir>/tsconfig-esm.spec.json',
        stringifyContentPathRegex: '\\.(html|svg)$',
        isolatedModules: true,
        useESM: true,
      },
    ],
  },
  moduleNameMapper: {
    ...pathsToModuleNameMapper(compilerOptions.paths, { prefix: '<rootDir>' }),
    tslib: 'tslib/tslib.es6.js',
  },
  setupFilesAfterEnv: ['<rootDir>/setup-jest.ts'],
};

export default jestConfig;

Before upgrading to ng13 and switching to ES Modules, your setup-jest.ts file most likely uses the preset setup-jest, like the following:

// setup-jest.ts
import 'jest-preset-angular/setup-jest';

or for ESM mode

// setup-jest.ts
import 'jest-preset-angular/setup-jest.mjs';

Potential issues with Angular 13 ESM package format and workaround

Cannot find modules error when importing any deep paths from Angular ESM format packages

Cannot find module '@angular/common/locales/xx' from 'src/app/app.component.spec.ts'

To fix this issue, one needs to add mjs to moduleFileExtensions as following

JavaScript

// jest.config.js
module.exports = {
  // ...other options
  moduleFileExtensions: ['ts', 'html', 'js', 'json', 'mjs'],
};

TypeScript

// jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  // ...other options
  moduleFileExtensions: ['ts', 'html', 'js', 'json', 'mjs'],
};

export default jestConfig;

Usage with Angular libraries which are built with Angular CLI 13

Besides, the changes in Angular packages themselves, Angular libraries which are built with Angular CLI 13 also introduce ESM package format. Similar to Angular packages, Jest doesn't understand .mjs files which are in these new format libraries in Jest CommonJS mode.

To fix this issue, one should modify transformIgnorePatterns to be as following:

JavaScript

// jest.config.js
module.exports = {
  // ...other options
  transformIgnorePatterns: ['node_modules/(?!.*\\.mjs$)'],
};

TypeScript

// jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  // ...other options
  transformIgnorePatterns: ['node_modules/(?!.*\\.mjs$)'],
};

export default jestConfig;

Usage with Ionic 6 or 7

To support Ionic 6 or 7 you will need to modify transformIgnorePatterns to be as following:

JavaScript

// jest.config.js
module.exports = {
  // ...other options
  transformIgnorePatterns: ['<rootDir>/node_modules/(?!(@ionic/core|@ionic/angular|@stencil/core|.*\\.mjs$))'],
};

TypeScript

// jest.config.ts
import type { Config } from 'jest';

const jestConfig: Config = {
  // ...other options
  transformIgnorePatterns: ['<rootDir>/node_modules/(?!(@ionic/core|@ionic/angular|@stencil/core|.*\\.mjs$))'],
};

export default jestConfig;