What is a Cypress preprocessor?
A Cypress preprocessor is the plugin responsible for preparing a support file or a test file for the browser.
The default Webpack preprocessor
By default, Cypress uses a Webpack preprocessor to transpile your test code and send it to the browser. The default Cypress Webpack config does the following things
- Transpiles ES2015+ and JSX via Babel.
- Transpiles TypeScript (how?).
- Watches and caches files.
You can customise the webpack config as shown here.