install in ubuntu

sudo apt-get install php-xdebug

phpunit.xml add this

<logging>
    <log type="coverage-html" target="./report" charset="UTF-8"
        yui="true" highlight="true"
        lowUpperBound="50" highLowerBound="80" />
</logging>

to run it

vendor/bin/phpunit

trouble

No code coverage driver is available
-> dont forget to install php-xdebug