⚡️ Speed Up Angular Testing with SWC 🦀
👀 What is this?
This is a set of Angular presets that enable you to use SWC (Speedy Web Compiler) with Jest or
Vitest.
Switching to SWC can speed up your tests by 2x to 12x.
🤔 Context
Surprisingly, in most cases, the bottleneck in Jest & Vitest tests is not the test execution time nor the Angular JIT
(Just-In-Time) compiler but the TypeScript transformer.
This is where SWC (Speedy Web Compiler) comes in. SWC is a JavaScript/TypeScript compiler that aims to be extremely
fast.
This package enables you to use SWC with Angular projects by setting the right configuration for SWC and using
our Angular plugin for SWC @jscutlery/swc-angular-plugin
🥇 Benchmark Summary

This chart is based on the benchmark where all caches were disabled as in most cases we will still have
to transform the code that we changed and which is affecting our tests.
In addition to that, incremental build tools like Nx (or jest/vitest changedSince
/changed
options) will reduce the amount of transforms.
Cf. Detailed Benchmark Data
🎭 Setup with Jest
1. Install
Install this preset and its dependencies via npm:
npm install -D @jscutlery/swc-angular @jscutlery/swc-angular-plugin @swc/core @swc/jest
grep .swc .gitignore || echo .swc >> .gitignore
2. Configure
In your Jest configuration file (e.g., jest.config.ts
), use the swcAngularJestTransformer
function to
transform .ts
, .js
, and .mjs
files.
import { swcAngularJestTransformer } from '@jscutlery/swc-angular';
export default {
transform: {
'^.+\\.(ts|mjs|js)$': swcAngularJestTransformer(),
'^.+\\.(html)$': [
'jest-preset-angular',
{
tsconfig: '<rootDir>/tsconfig.spec.json',
stringifyContentPathRegex: '\\.(html|svg)$',
},
],
},
transformIgnorePatterns: ['node_modules/(?!.*\\.mjs$)'],
};
3. Add reflect-metadata
In order for constructor injection to work, you need to import reflect-metadata
in the setup file which is probably
located at src/test-setup.ts
.
import 'reflect-metadata';
⚡️Setup with Vitest
1. Install
Install this preset and its dependencies via npm:
npm install -D @jscutlery/swc-angular @jscutlery/swc-angular-plugin @swc/core unplugin-swc
grep .swc .gitignore || echo .swc >> .gitignore
2. Configure
In your vite configuration file (e.g., vite.config.ts
), use the unplugin-swc
plugin with our
preset: swcAngularVitePreset
.
import { swcAngularUnpluginOptions } from '@jscutlery/swc-angular';
import swc from 'unplugin-swc';
import { defineConfig } from 'vite';
export default defineConfig({
plugins: [swc.vite(swcAngularUnpluginOptions())],
});
3. Add reflect-metadata
In order for constructor injection to work, you need to import reflect-metadata
in the setup file which is probably
located at src/test-setup.ts
.
import 'reflect-metadata';
🙋♂️ F.A.Q.
TypeScript property inheritance issue
If you encounter an issue with TypeScript property inheritance (Cf. https://github.com/jscutlery/devkit/issues/376), then you can try to disable the useDefineForClassFields
option:
swcAngularJestTransformer({ useDefineForClassFields: false });
or
swcAngularUnpluginOptions({ useDefineForClassFields: false });
🙏 Thanks to @santiagof4, @pumano, and @ryan-bendel.
🥇 Benchmark Data
🔥 No Cache
All caches are cleared before each benchmark run.
🥇vitest-swc-no-isolate | 1.00 | 3.137 ± 0.061 | 3.042 | 3.227 |
🥈jest-swc | 3.31 ± 0.15 | 10.393 ± 0.429 | 9.745 | 10.994 |
🥉angular-cli-karma | 3.52 ± 0.53 | 11.041 ± 1.642 | 10.218 | 15.690 |
angular-cli-web-test-runner | 5.46 ± 0.45 | 17.118 ± 1.362 | 16.473 | 20.911 |
jest | 5.78 ± 0.25 | 18.132 ± 0.716 | 17.553 | 19.998 |
angular-cli-jest | 8.61 ± 0.63 | 27.009 ± 1.902 | 24.938 | 30.450 |
vitest-swc | 8.94 ± 0.21 | 28.038 ± 0.402 | 27.539 | 28.617 |
vitest | 11.43 ± 0.32 | 35.872 ± 0.727 | 34.452 | 37.340 |
vitest-no-isolate | 11.49 ± 0.25 | 36.061 ± 0.369 | 35.414 | 36.502 |
⚡️ With Cache
All tests are ran once to warm up the cache before running the benchmark.
🥇vitest-swc-no-isolate | 1.00 | 3.092 ± 0.090 | 3.030 | 3.301 |
🥈angular-cli-karma | 1.91 ± 0.07 | 5.901 ± 0.139 | 5.718 | 6.131 |
🥉jest-swc | 2.93 ± 0.18 | 9.045 ± 0.494 | 8.513 | 10.065 |
jest | 4.07 ± 0.25 | 12.581 ± 0.663 | 11.572 | 13.915 |
angular-cli-web-test-runner | 5.96 ± 0.29 | 18.428 ± 0.711 | 17.497 | 19.262 |
angular-cli-jest | 8.46 ± 1.04 | 26.170 ± 3.117 | 23.350 | 31.983 |
vitest-swc | 9.28 ± 0.36 | 28.691 ± 0.728 | 27.977 | 30.488 |
vitest-no-isolate | 11.74 ± 0.45 | 36.286 ± 0.880 | 35.107 | 38.018 |
vitest | 12.18 ± 0.63 | 37.666 ± 1.625 | 35.563 | 41.503 |
🥱 Cold Start
Run a single test module just and try to measure the bootstrap time.
🥇vitest-swc-no-isolate | 1.00 | 1.260 ± 0.024 | 1.241 | 1.314 |
🥈vitest-swc | 1.00 ± 0.03 | 1.262 ± 0.026 | 1.225 | 1.305 |
🥉jest-swc | 1.44 ± 0.15 | 1.812 ± 0.186 | 1.714 | 2.310 |
vitest-no-isolate | 1.47 ± 0.05 | 1.846 ± 0.056 | 1.797 | 1.949 |
vitest | 1.61 ± 0.16 | 2.030 ± 0.198 | 1.814 | 2.423 |
jest | 1.69 ± 0.08 | 2.136 ± 0.094 | 2.017 | 2.356 |
angular-cli-jest | 1.73 ± 0.39 | 2.186 ± 0.495 | 1.869 | 3.119 |
angular-cli-web-test-runner | 2.06 ± 1.15 | 2.602 ± 1.451 | 2.080 | 6.730 |
angular-cli-karma | 5.08 ± 1.30 | 6.400 ± 1.636 | 5.377 | 10.177 |
Configurations
angular-cli-karma | Angular CLI's Karma | false |
angular-cli-jest | Angular CLI's Jest | true |
angular-cli-web-test-runner | Angular CLI's @web/test-runner | true |
jest | Jest | true |
jest-swc | Jest + SWC | true |
vitest | Vitest | true |
vitest-no-isolate | Vitest + No Isolation | false |
vitest-swc | Vitest + SWC | true |
vitest-swc-no-isolate | Vitest + SWC + No Isolation | false |
- Test Isolation: this tells whether each test module has its own testing environment or if each one is isolated. (i.e.
globals like the DOM are shared, asynchronous code might bleed between tests, etc...)
Source
💻 try it yourself: https://github.com/yjaaidi/experiments/tree/angular-swc-benchmark
or checkout the last benchmark results: https://github.com/yjaaidi/experiments/actions/workflows/benchmark.yml