If you want code coverage in your Tests, you can use one of pcov
(recommended) or xdebug
To enable pcov
put php -dpcov.enabled=1
before your script:
e.g: php -dpcov.enabled=1 vendor/bin/phpunit
!!! to use pcov with phpunit <=7.0 you need pcov/clobber
To enable xdebug
got to the Documentation about xdebug.md.