Plug-in “org.codecover.eclipse” was unable to instantiate class “org.codecover.eclipse.junit.JUnitLaunchConfigurationDelegate” while using JUnit

I've been trying to run my test classes with the CodeCover framework, but I am getting an error when I use the configuration Run As -> CodeCover Measurement for JUnit.

I am not sure what the problem is, as I have already ran these test classes successfully as junit tests. Please advise.