# Add Jest

This recipe helps you setup Jest in your Gatsby site to test components and utilities.

<Config
  name="gatsbyjs/add-jest"
/>

This recipe:

---

Installs the `jest` package.

<NPMPackage name="jest" />

---

Adds some jest test files for you to play with.

<File
  path="src/jest-example/sum.js"
  content="https://gist.github.com/KyleAMathews/3267b3e09b23dd693aa996b23dfd2d6f/raw/f7c8fa25c295421d8826037b40ac924a33aebf15/sum.js"
/>

<File
  path="src/jest-example/sum.test.js"
  content="https://gist.github.com/KyleAMathews/3267b3e09b23dd693aa996b23dfd2d6f/raw/f7c8fa25c295421d8826037b40ac924a33aebf15/sum.test.js"
/>

---

Adds a `test` & `test:watch` scripts to your `package.json`.

<NPMScript
  name="test"
  command="jest"
/>

<NPMScript
  name="test:watch"
  command="jest --watch"
/>

---

Once you've installed this recipe, try running `npm run test` and jest will run your test. And, while writing tests, you can run `npm run test:watch` and tests will re-run
as you edit them.