isabella232 / instrument-cra

Little module for CRA applications to instrument code without ejecting react-scripts

@cypress/instrument-cra

Little module for CRA applications to instrument code without ejecting react-scripts

Install and use

yarn add @cypress/instrument-cra

Then change your npm start script to require this module before starting the dev server

{
  "scripts": {
    "start": "react-scripts -r @cypress/instrument-cra start",
  }
}

This module assumes standard Create-React-App v3 JavaScript application with source files in the "src" folder.

When the app starts with yarn start, you should see the coverage information under window.__coverage__ information.

The instrumentation is done using Istanbul.js via babel-plugin-istanbul and is compatible with @cypress/code-coverage plugin.

Exclude files

If you want to exclude files from coverage, for example src/serviceWorker.js, add an object named nyc to package.json following the nyc CLI configuration.

{
  "nyc": {
    "exclude": "src/serviceWorker.js"
  }
}

Instrument a fork

To instrument a fork of react-scripts, provide the path to the new webpack.config.js in your package.json as cypressWebpackConfigPath, e.g.:

{
  "cypressWebpackConfigPath": "./node_modules/@my-org/my-react-scripts-fork/config/webpack.config.js"
}

Force instrumentation

Usually, the code is only instrumented in the development environment. If you want to force the instrumentation, set the environment variable

CYPRESS_INSTRUMENT_PRODUCTION=true

Debugging

Run with environment variable DEBUG=instrument-cra to see the verbose logs

Notes

If you try to start the application, and react-scripts shows an error There might be a problem with the project dependency tree., just create a local file .env with. The problem is due to several versions of babel-loader dependency between this plugin and your application.

SKIP_PREFLIGHT_CHECK=true

Examples

In this repository

• react-scripts v3
• react-scripts v4

External

• React JavaScript app
• React TypeScript app

License

MIT License, see LICENSE