diff --git a/src/Data/Range.hs b/src/Data/Range.hs
index 607d5815a..e4f725b77 100644
--- a/src/Data/Range.hs
+++ b/src/Data/Range.hs
@@ -32,6 +32,13 @@ subtractRange range1 range2 = Range (start range1) (end range1 - rangeLength (Ra
 
 -- Instances
 
+-- $setup
+-- >>> import Test.QuickCheck
+-- >>> instance Arbitrary Range where arbitrary = Range <$> arbitrary <*> arbitrary
+
+-- $
+-- Associativity:
+-- prop> \ a b c -> a <> (b <> c) == (a <> b) <> (c :: Range)
 instance Semigroup Range where
   Range start1 end1 <> Range start2 end2 = Range (min start1 start2) (max end1 end2)