File: phpunit.xml

<?xml version="1.0" encoding="UTF-8"?>

<phpunit bootstrap="app/Bootstrap.php" colors="true">

    <testsuites>
        <testsuite name="AppTests">
            <directory suffix="Test.php">./tests/</directory>
        </testsuite>
    </testsuites>

    <filter>
        <whitelist>
            <directory suffix=".php">src</directory>
        </whitelist>
    </filter>

</phpunit>