In order of preference:
composer require wp-phpunit/wp-phpunit --dev. Depending on the IDE you use you might need to mark the package in
vendor/as a source directory.
- Each IDE allows you to add definitions from external libraries. In PHPStorm it’s
Settings → Languages & Frameworks → PHP → Include Path.
- Just copy the files over to some directory in your project and exclude them with
.gitignore(if you use Git for version control).