servant-mock: add simple test case

servant-mock/servant-mock.cabal

@@ -58,5 +58,9 @@ test-suite spec
   build-depends:
     base,
     hspec,
+    hspec-wai,
+    QuickCheck,
     servant,
-    servant-mock
+    servant-server,
+    servant-mock,
+    aeson

servant-mock/test/Servant/MockSpec.hs

@@ -1,12 +1,42 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DeriveAnyClass #-}
+{-# LANGUAGE DeriveGeneric #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE TypeOperators #-}
 
 module Servant.MockSpec where
 
-import           Test.Hspec
+import           Data.Aeson as Aeson
+import           Data.Proxy
+import           GHC.Generics
+import           Servant.API
+import           Test.Hspec hiding (pending)
+import           Test.Hspec.Wai
+import           Test.QuickCheck
 
+import           Servant
 import           Servant.API.Internal.Test.ComprehensiveAPI
 import           Servant.Mock
 
 _ = mock comprehensiveAPI
 
+data Body
+  = Body
+  | ArbitraryBody
+  deriving (Generic, ToJSON)
+
+instance Arbitrary Body where
+  arbitrary = return ArbitraryBody
+
 spec :: Spec
-spec = return ()
+spec = do
+  describe "mock" $ do
+    context "Get" $ do
+      let api :: Proxy (Get '[JSON] Body)
+          api = Proxy
+          app = serve api (mock api)
+      with (return app) $ do
+        it "serves arbitrary response bodies" $ do
+          get "/" `shouldRespondWith` 200{
+            matchBody = Just $ Aeson.encode ArbitraryBody
+          }