src/test/resources/com/puppycrawl/tools/checkstyle/main/InputMainConfig-non-existing-classname.xml

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

<!DOCTYPE module PUBLIC
        "-//Puppy Crawl//DTD Check Configuration 1.1//EN"
        "http://checkstyle.sourceforge.net/dtds/configuration_1_1.dtd">

<module name="Checker">
    <module name="TreeWalker">
        <module name="NonExistingClass">
            <property name="severity" value="warning"/>
        </module>
    </module>
</module>