This plugin integrates with Grails 2.x and is no longer maintained.
Consider using a Gradle Clover Plugin for Grails 3.0 and newer.
What is Clover-for-Grails?
Clover-for-Grails integrates the industry-leading code coverage tool, Clover with the Grails web application development framework. Clover-for-Grails allows you to easily measure the coverage of your unit tests, enabling targeted work in unit testing — resulting in stability and enhanced quality code with maximal efficiency of effort.