Cobertura plugin for maven 2. cobertura is a free java tool that calculates the percentage of code accessed by tests. it can be used to identify which parts of your java program are lacking test coverage. this plugin provides the features of cobertura within the maven 2 environment. the report generated by this plugin is the result of executing the cobertura tool against your compiled classes to help you determine how well the unit testing efforts have been, and can then be used to identify which parts of your java program are lacking test coverage.