diff --git a/tests/hspec/MapSpec.hs b/tests/hspec/MapSpec.hs
index b1cabbe..ca13c94 100644
--- a/tests/hspec/MapSpec.hs
+++ b/tests/hspec/MapSpec.hs
@@ -15,9 +15,19 @@ myMap2 = ext (Var :: (Var "w")) (2::Int) $ ext (Var :: (Var "z")) (4::Int) empty
 
 spec :: Spec
 spec = do
-  describe "Map tests" $
-    it "Map tests" $ do
+  describe "Map tests" $ do
+    it "foo map lookups" $ do
       (lookp (Var @"x") Example.foo)  `shouldBe` (2 :: Int)
       (lookp (Var @"w") Example.foo)  `shouldBe` (5 :: Int)
       (lookp (Var @"z") Example.foo)  `shouldBe` True
       (mapLength Example.foo) `shouldBe` 3
+    it "bar map lookups" $ do
+      (lookp (Var @"y") Example.bar)  `shouldBe` (3 :: Int)
+      (lookp (Var @"w") Example.bar)  `shouldBe` (1 :: Int)
+      (mapLength Example.bar) `shouldBe` 2
+    it "foobar union combines values correctly" $ do
+      (lookp (Var @"w") Example.foobar) `shouldBe` (6 :: Int)  -- 5 + 1 combined
+      (lookp (Var @"x") Example.foobar) `shouldBe` (2 :: Int)
+      (lookp (Var @"y") Example.foobar) `shouldBe` (3 :: Int)
+      (lookp (Var @"z") Example.foobar) `shouldBe` True
+      (mapLength Example.foobar) `shouldBe` 4
diff --git a/tests/hspec/SetSpec.hs b/tests/hspec/SetSpec.hs
index fbf1626..f43b935 100644
--- a/tests/hspec/SetSpec.hs
+++ b/tests/hspec/SetSpec.hs
@@ -7,6 +7,7 @@ module SetSpec where
 
 import Test.Hspec
 import Data.Type.Set
+import qualified ExampleSet
 import ExampleSet2
 
 spec :: Spec
@@ -20,3 +21,9 @@ spec = do
       barHasNat1 `shouldBe` False
     it "Union of large sets should run in reasonable time" $ do
       (r0_9 `union` r10_19) `shouldBe` (r0_9 `append` r10_19)
+  describe "Natural set example from README" $ do
+    it "foo, bar, and foobar unions compile successfully" $ do
+      -- These are mainly type-level tests - if they compile, they work
+      show ExampleSet.foo `shouldSatisfy` (not . null)
+      show ExampleSet.bar `shouldSatisfy` (not . null)
+      show ExampleSet.foobar `shouldSatisfy` (not . null)