I'm not familiar with SonarQube at all so I'm not sure if this will help but Codename One does have a unit test API of its own and test recorder that is probably not supported by SonarQube: http://www.codenameone.com/3/post/2012/12/test-it.html
The reason for not using JUnit and other such harnesses is that they usually rely on reflection to get the job done and that's a problem for on device testing across platforms.