phpunit.xml

<phpunit
        bootstrap="web/core/tests/bootstrap.php"
        colors="true"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/4.5/phpunit.xsd"
        convertErrorsToExceptions="true"
        convertNoticesToExceptions="true"
        convertWarningsToExceptions="true">
    <testsuites>
        <testsuite name="Custom modules">
            <directory>docroot/modules/custom/*/tests</directory>
        </testsuite>
    </testsuites>
    <filter>
        <whitelist processUncoveredFilesFromWhitelist="true">
            <directory suffix=".php">docroot/modules/custom</directory>
            <exclude>
                <directory suffix=".php">docroot/modules/custom/*/tests</directory>
            </exclude>
        </whitelist>
    </filter>
</phpunit>