How to skip compile irrelevant class when using testOnly in Play! Framework's Activator

I am refactoring my Play! Framework project. When I edit code in a file, it will make the others files full of errors.

I don't want to go all the place to fix the errors. Instead, I write a unit test to test the class I am fixing one by one. To run the unit test, I use Activator's testOnly command. It worked at first, but after I once run the clean command, the testOnly command starts compile all files in the project, which results in compilation failed.

How to tell to testOnly command to compile only the relevant code used in the unit test.