Summary

The failOnPhpunitWarning phpunit attribute configuration doesn't work.
It is not mentioned in the documentation, but is present in the phpunit.xsd file.

Current behavior

When I run tests with --do-not-fail-on-phpunit-warning cli option, I have no errors.
When I run tests with the failOnPhpunitWarning phpunit attribute configuration, I have an error.

How to reproduce

<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="vendor/phpunit/phpunit/phpunit.xsd"
        bootstrap="vendor/autoload.php"
        failOnPhpunitWarning="false"
>

Expected behavior

No longer have errors when using failOnPhpunitWarning phpunit attribute configuration.