And only on this method the test fail on should:

testCellOnState
      | cell |
      cell := BlankCell new.
      cell should: [ cell isOff ].
      cell shouldnt:  [ cell isOn ].

Yes it does, inasmuch on the bottom of this page ( http://squeak.preeminent.org/tut2007/html/017.html )

both methods return false. I think later the implementation of this two methods will be changed so don't worry.