replacing known values in output now (pretty sick)

test/NicetiesSpec.hs

@@ -0,0 +1,19 @@
+module NicetiesSpec (spec) where
+
+import Bruijn (toDeBruijn)
+import Niceties (findKnown, replaceKnowns)
+import Parser (Expr (Abstraction, Application, Variable))
+import Test.Hspec
+
+spec :: Spec
+spec = do
+  describe "can find knowns" $ do
+    it "can find identity" $
+      findKnown identity `shouldBe` Just "I"
+  describe "replaceKnowns" $ do
+    it "can replace identity" $
+      replaceKnowns identity `shouldBe` Variable "I"
+    it "can replace identity of identity" $
+      replaceKnowns (Application identity identity) `shouldBe` Application (Variable "I") (Variable "I")
+  where
+    identity = toDeBruijn $ Abstraction "x" (Variable "x")