Automated test coverage of the priority sorter plugin is low. Improve the automated test coverage by submitting pull requests with new automated tests.
Review the current test coverage with the commands:
Most integrated development environments have tools that will create a test stub that is a good beginning. Apache Netbeans has "Create / Update tests" . JetBrains IntelliJ has "Create tests". Visual Studio Code has the "Extension Pack for Java".
Use the IDE or your own coding to create a test for one of the classes that is not well covered by tests.
Keep the test small so that the pull request is easy to review.