[tests] Add a test for button group
[tests] Add a test for button group

jonnylamb/mx,pwithnall/mx,clutter-project/mx,pwithnall/mx,jonnylamb/mx,clutter-project/mx,jonnylamb/mx,clutter-project/mx,pwithnall/mx,clutter-project/mx,jonnylamb/mx,pwithnall/mx