phpunit.xml

<phpunit
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/6.5/phpunit.xsd"
        bootstrap="vendor/autoload.php"
>
    <testsuites>
        <testsuite name="Unit Tests">
            <directory>tests</directory>
        </testsuite>
    </testsuites>

    <filter>
        <whitelist>
            <directory suffix=".php">./</directory>
            <exclude>
                <directory>tests/</directory>
            </exclude>
        </whitelist>
    </filter>
</phpunit>