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.
Jest ESM support with Angular 13 is new and may have issues.
Starting from v11.0.0, jest-preset-angular
introduces a few extra changes to be able to run Jest with Angular 13:
-
ng-jest-resolver
is introduced as a custom Jest resolver to resolve.mjs
files. -
moduleFileExtensions
is updated to includemjs
files as accepted module format. -
transformIgnorePatterns
is added to inform Jest to transform.mjs
files. -
transform
is updated to include.mjs
extension to transform toCommonJS
codes.
Migration steps from Angular < 13
-
Upgrade the project to Angular 13 following guide
-
If one is using the default preset as following:
// jest.config.js
module.exports = {
preset: 'jest-preset-angular',
};
there are no migration steps required
- If one is NOT having
preset: 'jest-preset-angular'
in Jest config, the config needs to be updated with new values forresolver
,transformIgnorePatterns
andtransform
:
// jest.config.js
module.exports = {
// ...other options
moduleFileExtensions: ['ts', 'html', 'js', 'json', 'mjs'],
resolver: 'jest-preset-angular/build/resolvers/ng-jest-resolver.js',
transformIgnorePatterns: ['node_modules/(?!.*\\.mjs$)'],
transform: {
'^.+\\.(ts|js|mjs|html|svg)$': 'jest-preset-angular',
},
};
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:
const { pathsToModuleNameMapper } = require('ts-jest/utils');
const { paths } = require('./tsconfig.json').compilerOptions;
/** @type {import('ts-jest/dist/types').InitialOptionsTsJest} */
module.exports = {
preset: 'jest-preset-angular/presets/defaults-esm',
globals: {
'ts-jest': {
useESM: true,
stringifyContentPathRegex: '\\.(html|svg)$',
tsconfig: '<rootDir>/tsconfig-esm.spec.json',
},
},
moduleNameMapper: {
...pathsToModuleNameMapper(paths, { prefix: '<rootDir>' }),
tslib: 'tslib/tslib.es6.js',
},
setupFilesAfterEnv: ['<rootDir>/setup-jest.ts'],
};
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';
import './jest-global-mocks';
The jest-preset-angular/setup-jest
file doesn't work with ESM, because it uses require
. For now you should skip using this file, and replace the contents of your setup-jest.ts
with:
// setup-jest.ts
import 'zone.js';
import 'zone.js/testing';
import './jest-global-mocks';
import { getTestBed } from '@angular/core/testing';
import { BrowserDynamicTestingModule, platformBrowserDynamicTesting } from '@angular/platform-browser-dynamic/testing';
getTestBed().initTestEnvironment(BrowserDynamicTestingModule, platformBrowserDynamicTesting(), {
teardown: {
destroyAfterEach: true, // Angular recommends this, but it may break existing tests
},
});
getTestBed().initTestEnvironment(BrowserDynamicTestingModule, platformBrowserDynamicTesting());
Potential issues with Angular 13 ESM package format and workaround
Cannot find modules
error when importing any deep paths from Angular ESM format packages
- Angular 13 ESM package format makes Jest resolution not able to resolve the correct
.mjs
files. Even though we introducedng-jest-resolver
as a part of the preset, this resolver won't work for all scenarios. One might get Jest error like
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
// jest.config.js
module.exports = {
// ...other options
moduleFileExtensions: ['ts', 'html', 'js', 'json', 'mjs'],
};
If the issue still persists, you might need to configure moduleNameMapper or extend the behavior the default resolver of this preset.
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:
// jest.config.js
module.exports = {
// ...other options
transformIgnorePatterns: ['node_modules/(?!.*\\.mjs$)'],
};