diff --git a/aeson-casing.cabal b/aeson-casing.cabal
--- a/aeson-casing.cabal
+++ b/aeson-casing.cabal
@@ -1,6 +1,6 @@
 
 name:                aeson-casing
-version:             0.1.0.3
+version:             0.1.0.4
 synopsis:            Tools to change the formatting of field names in Aeson
                      instances.
 description:         Tools to change the formatting of field names in Aeson
@@ -33,6 +33,8 @@
     main-is:            Main.hs
     hs-source-dirs:     test
     default-language:   Haskell2010
+
+    other-modules:      Data.Aeson.Casing.Test
 
     build-depends:      base                >=4.7   && <5.0
                     ,   tasty
diff --git a/test/Data/Aeson/Casing/Test.hs b/test/Data/Aeson/Casing/Test.hs
new file mode 100644
--- /dev/null
+++ b/test/Data/Aeson/Casing/Test.hs
@@ -0,0 +1,55 @@
+{-# LANGUAGE DeriveGeneric     #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TemplateHaskell   #-}
+
+module Data.Aeson.Casing.Test (tests) where
+
+import           Data.Aeson
+import           GHC.Generics
+import           Test.Tasty
+import           Test.Tasty.HUnit
+import           Test.Tasty.TH
+
+import           Data.Aeson.Casing.Internal
+
+tests :: TestTree
+tests = $(testGroupGenerator)
+
+case_snake :: Assertion
+case_snake = do snakeCase "SampleField" @=? "sample_field"
+                snakeCase "sampleField" @=? "sample_field"
+
+case_camel :: Assertion
+case_camel = do camelCase "SampleField" @=? "sampleField"
+                camelCase "sampleField" @=? "sampleField"
+
+case_pascal :: Assertion
+case_pascal = do pascalCase "SampleField" @=? "SampleField"
+                 pascalCase "sampleField" @=? "SampleField"
+
+case_prefix :: Assertion
+case_prefix = dropFPrefix "extraSampleField" @=? "SampleField"
+
+----
+
+data Person = Person
+        { personFirstName :: String
+        , personLastName  :: String
+        } deriving (Eq, Show, Generic)
+
+instance ToJSON Person where
+    toJSON = genericToJSON $ aesonPrefix snakeCase
+instance FromJSON Person where
+    parseJSON = genericParseJSON $ aesonPrefix snakeCase
+
+case_encode_snake :: Assertion
+case_encode_snake = do
+        let p = Person "John" "Doe"
+            b = encode p
+        b @=? "{\"first_name\":\"John\",\"last_name\":\"Doe\"}"
+
+case_decode_snake :: Assertion
+case_decode_snake = do
+        let b = "{\"first_name\":\"John\",\"last_name\":\"Doe\"}"
+            p = decode b :: Maybe Person
+        p @=? Just (Person "John" "Doe")