+
+
+-- Quickcheck tests.
+
+-- | Since the grid size is necessarily positive, all tetrahedrons
+-- (which comprise cubes of positive volume) must have positive volume
+-- as well.
+-- prop_all_volumes_positive :: Cube -> Property
+-- prop_all_volumes_positive c =
+-- (delta > 0) ==> (null nonpositive_volumes)
+-- where
+-- delta = h (grid c)
+-- ts = tetrahedrons c
+-- volumes = map volume ts
+-- nonpositive_volumes = filter (<= 0) volumes