ts-jest VS svelte-preprocess

use ts-jest and set up Paths Re-Map

ts-jest has had some strange performance issues and workarounds in the past, though I haven’t used it very recently so it might have fixed those by now.

Since we're working with TypeScript, we can use ts-jest, which conveniently brings Jest along for the ride:

I want to save you from manually copying the snippets one by one, so here is a Gist with the complete test file. This can be easily executed with Jest (or ts-jest for TypeScript).

See the Jest configuration docs to learn more about Jest configuration. ts-jest also has good documentation.

Using @swc/jest to compile code to CommonJS is much faster than babel-jest, ts-jest which have long cold starts when executing tests in a large project.

ts-jest: A transformer for handling TypeScript files.

Thankfully using TypeScript and TypeScript project references makes the intricate problem of using Jest easier since we can make use of the excellent ts-jest Jest transformer. All we need to do it point ts-jest to the respective tsconfig.json file for each package (see example jest.config.js). Since we have configured TypeScript to be composite and incremental, we do not need to recompile TypeScript for dependencies of a package we want to test, which significantly reduces the runtime for unit tests. ts-jest will also ensure that any error message will reference the line numbers in the source TypeScript files.

We need to configure Jest to transform our files. We must explicitly set our test environment to jsdom, which we are using through Jest. Since v27 Jest's default test environment is node. I will put the configuration in a specific Jest configuration file called jest.config.json in the project root folder. If you create a configuration file called jest.config.js, Vite will complain as it expects only ESM JavaScript by default. Vite will recommend that you rename it to a ".cjs" file if you want to do it that way. You can look at the different ways to configure Jest if you are unsure about the file conventions. If you're using TypeScript, you need to configure svelte-preprocess and ts-jest also, see the svelte-jester docs for how to do that.

svelte-preprocess is responsible for processing things like TypeScript and SCSS. The svelte compiler itself is only responsible for turning the svelte file into JavaScript.

svelte-preprocess should handle scss out-of-the-box, and it’s included in SvelteKit by default if you created your project with create-svelte

Have you tried https://github.com/sveltejs/svelte-preprocess

// svelte.config.js import preprocess from 'svelte-preprocess' import adapter from '@sveltejs/adapter-static' /** @type {import('@sveltejs/kit').Config} */ const config = { // Consult https://github.com/sveltejs/svelte-preprocess // for more information about preprocessors preprocess: [preprocess({ postcss: true })], kit: { // I can even build php file which I can use in current project seamlessly! adapter: adapter({ fallback: 'myapp.php' }), files: { assets: 'src/assets', }, appDir: 'myapp', } } export default config

/** @type {import('@sveltejs/kit').Config} */ const config = { // Consult https://github.com/sveltejs/svelte-preprocess // for more information about preprocessors preprocess: preprocess(),

We need to configure Jest to transform our files. We must explicitly set our test environment to jsdom, which we are using through Jest. Since v27 Jest's default test environment is node. I will put the configuration in a specific Jest configuration file called jest.config.json in the project root folder. If you create a configuration file called jest.config.js, Vite will complain as it expects only ESM JavaScript by default. Vite will recommend that you rename it to a ".cjs" file if you want to do it that way. You can look at the different ways to configure Jest if you are unsure about the file conventions. If you're using TypeScript, you need to configure svelte-preprocess and ts-jest also, see the svelte-jester docs for how to do that.

If you want to write pug, there are tools that allow you to do that: https://github.com/sveltejs/svelte-preprocess

All this file does is export a configuration object for the build of our Svelte application. By default, it uses the svelte-preprocess package, which is a preprocessor for Svelte providing support for PostCSS, SCSS, TypeScript, and much more.

import preprocess from 'svelte-preprocess' import path, { dirname } from 'path' import { fileURLToPath } from 'url' import adapter from '@sveltejs/adapter-node' const filePath = dirname(fileURLToPath(import.meta.url)) const sassPath = `${filePath}/src/lib/style/` const config = { // Consult https://github.com/sveltejs/svelte-preprocess // for more information about preprocessors preprocess: preprocess({ scss: { prependData: `@import '${sassPath}_global-imports.scss';` } }), .... } export default config

import adapter from '@sveltejs/adapter-vercel' import { mdsvex } from 'mdsvex' import preprocess from 'svelte-preprocess' import mdsvexConfig from './mdsvex.config.js' /** @type {import('@sveltejs/kit').Config} */ const config = { extensions: ['.svelte', ...mdsvexConfig.extensions], // Consult https://github.com/sveltejs/svelte-preprocess // for more information about preprocessors preprocess: [ mdsvex(mdsvexConfig), [ preprocess({ postcss: true, }), ], ], kit: { target: '#svelte', adapter: adapter(), }, } export default config // Workaround until SvelteKit uses Vite 2.3.8 (and it's confirmed to fix the Tailwind JIT problem) const mode = process.env.NODE_ENV const dev = mode === 'development' process.env.TAILWIND_MODE = dev ? 'watch' : 'build'