Starting with maven-checkstyle-plugin version 2.14, config/maven_checks.xml predefined ruleset is not part of the plugin any more but has moved to Apache Maven Shared Resources.
You can set the Checkstyle properties to be used in the plugin configuration of your POM through the propertiesLocation parameter. The properties file will be resolved by the plugin based on its value.
You can set a custom ruleset through the configLocation plugin parameter. If no value is specified, the plugin will use a default ruleset, which is the sun_checks.xml, that is bundled with the plugin.
You can include the test directory in the Checkstyle report by setting the includeTestSourceDirectory plugin parameter to true.
The checkstyle:checkstyle goal is a reporting goal that adds a report of Checkstyle violations to the output of the maven-site-plugin. The checkstyle:check goal is an ordinary goal that reports violations to the console and/or fails the build when there are violations.