Use View -> Quick Documentation or the corresponding keyboard shortcut (depends on OS and Keymap).
On Mac OSX with Eclipse keymap, F2 Works.
It's also possible to enable automatic JavaDoc popup on code completion in Preferences -> Editor -> Code completion (Autopopup documentation).
At the beginning this worked for me (somewhat clitching), but now it no longer works :(
To run the Headless-App-Tests in JUnit (e.g. for debugging), create/add a new JUnit Configuration. In the configuration, it is important to select "class" at the dropdown for the "Form mode" (upper right). I also recommend to use "Single instance only".
If "Fork mode: class" is not selected, JUnit seems to use different JVMs to execute test and parameter method, which causes the ArticleManager in the test method to be empty.