Setup

We recommend using Jest but you're free to use the library with any testing framework and runner you're comfortable with.

Jest

Install Jest
npm install --save-dev jest
Add the following to your package.json
{
"scripts": {
"test": "jest src",
"test:watch": "npm run test -- --watch"
}
}
You'll need to compile the Svelte components before using them in Jest, so we need to install svelte-jester
npm install --save-dev svelte-jester
Add the following Jest configuration to your package.json
{
"jest": {
"transform": {
"^.+\\.svelte$": "svelte-jester"
},
"moduleFileExtensions": ["js", "svelte"]
}
}
If you are using ES6 modules in your project you have to add Jest's babel transform setting (it is set by default, but since we are overriding the transform config, we have to add it explicitly)
5.1 Install babel-jest
npm install --save-dev babel-jest
5.2. Add a basic .babelrc configuration
{
"presets": [["@babel/preset-env", { "targets": { "node": "current" } }]]
}
5.3. Update the Jest transform configuration
"transform": {
"^.+\\.js$": "babel-jest",
"^.+\\.svelte$": "svelte-jester"
},
This is optional but it is recommended, you can install jest-dom to add handy assertions to Jest
6.1 Install jest-dom
npm install --save-dev @testing-library/jest-dom
6.2 Add the following to your Jest configuration in package.json
{
"setupFilesAfterEnv": ["@testing-library/jest-dom/extend-expect"]
}
Create your component + test file (checkout the rest of the docs to see how) and run it
npm run test

To use Typescript, you'll need to install and configure svelte-preprocess and ts-jest. For full instructions, see the svelte-jester docs.

If you'd like to also include any Svelte preprocessors then simply follow the instructions over at svelte-jester.