How to use PHPUnit code-coverage-tool PCOV in PhpStorm

Question

I use PHP 7.4.13, PhpStorm 2020.1.4, PHPUnit 9.5.8.

I try to use PHPUnit code coverage tool with PCOV, but I don't get it to work.

I installed pcov: pecl install pcov

I enabled the extension in the php.ini file: extension="pcov.so"

My phpunit.xml looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<phpunit backupGlobals="false"
         backupStaticAttributes="false"
         bootstrap="vendor/autoload.php"
         colors="true"
         convertErrorsToExceptions="true"
         convertNoticesToExceptions="true"
         convertWarningsToExceptions="true"
         processIsolation="false"
         stopOnFailure="false">
    <testsuites>
        <testsuite name="Unit">
            <directory suffix="Test.php">./tests/Unit</directory>
        </testsuite>

        <testsuite name="Integration">
            <directory suffix="Test.php">./tests/Integration</directory>
        </testsuite>
    </testsuites>
    <filter>
        <whitelist processUncoveredFilesFromWhitelist="true">
            <directory suffix=".php">./app</directory>
        </whitelist>
    </filter>
    <php>
        <server name="APP_ENV" value="testing"/>
        <server name="BCRYPT_ROUNDS" value="4"/>
        <server name="CACHE_DRIVER" value="array"/>
        <server name="MAIL_DRIVER" value="array"/>
        <server name="QUEUE_CONNECTION" value="sync"/>
        <server name="SESSION_DRIVER" value="array"/>
        <server name="DB_DATABASE" value="testing"/>
    </php>
</phpunit>

When I try to run phpunit --coverage-html coverage I get the following:

I think the problem is the missing coverage driver. But where does the problem come from and how can I fix it?

I'm trying to solve this problem since 3 hours now, but I cant find a way.

I hope someone can help :)