I found a solution on Stack Overflow for Java program run configurations which also works for JUnit run configurations.
You can get the full command executed by your configuration on the Debug tab, or more specifically the Debug view.
- Run your application
- Go to your Debug perspective
- There should be an entry in there (in the Debug View) for the app you've just executed
- Right-click the node which references java.exe or javaw.exe and select Properties In the dialog that pops up you'll see the Command Line which includes all jars, parameters, etc