deeper test for differentiate. back to 100% coverage

darcs-hash:20070930075018-cba2c-48c2b170e452ef6db4957c1088ef9ab4d42a7505

1 files changed, 1 insertions, 1 deletions

diff --git a/tests/Properties.hs b/tests/Properties.hs
index 447dae8..2bc5443 100644
--- a/tests/Properties.hs
+++ b/tests/Properties.hs
@@ -547,7 +547,7 @@ prop_screens (x :: T) = n `elem` screens x
 
 prop_differentiate xs =
         if null xs then differentiate xs == Nothing
-                   else focus (fromJust (differentiate xs)) == head xs
+                   else (differentiate xs) == Just (Stack (head xs) [] (tail xs))
     where _ = xs :: [Int]
 
 -- looking up the tag of the current workspace should always produce a tag.