diff --git a/driver/Main.hs b/driver/Main.hs
--- a/driver/Main.hs
+++ b/driver/Main.hs
@@ -2,14 +2,16 @@
 
 import           Prelude ()
 import           Prelude.Compat
-import           Control.Monad.Compat
+
+import           Control.DeepSeq
 import           Control.Exception
-import           System.IO
-import           System.IO.Error
+import           Control.Monad.Compat
 import           Data.List.Compat
 import           Data.Version (showVersion)
-import           Control.DeepSeq
 import           System.Environment
+import           System.Exit
+import           System.IO
+import           System.IO.Error
 
 import           Paths_hpack (version)
 import           Hpack.Config
@@ -29,17 +31,29 @@
 main :: IO ()
 main = do
   args <- getArgs
-  if "--version" `elem` args
-    then putStrLn programVersion
-    else do
-      (warnings, name, new) <- run
-      forM_ warnings $ \warning -> hPutStrLn stderr ("WARNING: " ++ warning)
-      old <- force . either (const Nothing) (Just . stripHeader) <$> tryJust (guard . isDoesNotExistError) (readFile name)
-      if (old == Just (lines new)) then do
-        putStrLn (name ++ " is up-to-date")
-      else do
-        (writeFile name $ header ++ new)
-        putStrLn ("generated " ++ name)
-      where
-        stripHeader :: String -> [String]
-        stripHeader = dropWhile null . dropWhile ("--" `isPrefixOf`) . lines
+  case args of
+    ["--version"] -> putStrLn programVersion
+    ["--silent"] -> hpack False
+    [] -> hpack True
+    _ -> do
+      hPutStrLn stderr "Usage: hpack [ --version | --silent ]"
+      exitFailure
+
+hpack :: Bool -> IO ()
+hpack verbose = do
+  (warnings, name, new) <- run
+  forM_ warnings $ \warning -> hPutStrLn stderr ("WARNING: " ++ warning)
+  old <- force . either (const Nothing) (Just . stripHeader) <$> tryJust (guard . isDoesNotExistError) (readFile name)
+  if (old == Just (lines new)) then do
+    output (name ++ " is up-to-date")
+  else do
+    (writeFile name $ header ++ new)
+    output ("generated " ++ name)
+  where
+    stripHeader :: String -> [String]
+    stripHeader = dropWhile null . dropWhile ("--" `isPrefixOf`) . lines
+
+    output :: String -> IO ()
+    output message
+      | verbose = putStrLn message
+      | otherwise = return ()
diff --git a/hpack.cabal b/hpack.cabal
--- a/hpack.cabal
+++ b/hpack.cabal
@@ -1,10 +1,11 @@
--- This file has been generated from package.yaml by hpack version 0.5.3.
+-- This file has been generated from package.yaml by hpack version 0.5.4.
 --
 -- see: https://github.com/sol/hpack
 
 name:           hpack
-version:        0.5.4
+version:        0.6.0
 synopsis:       An alternative format for Haskell packages
+category:       Development
 homepage:       https://github.com/sol/hpack#readme
 bug-reports:    https://github.com/sol/hpack/issues
 maintainer:     Simon Hengel <sol@typeful.net>
@@ -35,6 +36,7 @@
   exposed-modules:
       Hpack.Config
       Hpack.Run
+      Hpack.Yaml
   other-modules:
       Hpack.GenericsUtil
       Hpack.Haskell
@@ -68,6 +70,7 @@
       test
     , src
   ghc-options: -Wall
+  cpp-options: -DTEST
   build-depends:
       aeson >= 0.8
     , base >= 4.7 && < 5
@@ -97,4 +100,5 @@
       Hpack.Render
       Hpack.Run
       Hpack.Util
+      Hpack.Yaml
   default-language: Haskell2010
diff --git a/src/Hpack/Config.hs b/src/Hpack/Config.hs
--- a/src/Hpack/Config.hs
+++ b/src/Hpack/Config.hs
@@ -7,9 +7,11 @@
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE CPP #-}
 module Hpack.Config (
   packageConfig
 , readPackageConfig
+, package
 , Package(..)
 , Dependency(..)
 , GitRef(..)
@@ -19,9 +21,9 @@
 , Library(..)
 , Executable(..)
 , SourceRepository(..)
-
--- exported for testing
+#ifdef TEST
 , getModules
+#endif
 ) where
 
 import           Control.Applicative
@@ -30,22 +32,25 @@
 import           Data.Data
 import           Data.HashMap.Lazy (HashMap)
 import qualified Data.HashMap.Lazy as Map
-import           Data.Ord
 import           Data.List (nub, (\\), sortBy)
 import           Data.Maybe
+import           Data.Ord
 import           Data.String
 import           Data.Text (Text)
 import qualified Data.Text as T
-import           Data.Yaml
 import           GHC.Generics
 import           Prelude ()
 import           Prelude.Compat
 import           System.Directory
 import           System.FilePath
 
-import           Hpack.Util
 import           Hpack.GenericsUtil
+import           Hpack.Util
+import           Hpack.Yaml
 
+package :: String -> String -> Package
+package name version = Package name version Nothing Nothing Nothing Nothing Nothing Nothing [] [] [] Nothing Nothing Nothing [] [] Nothing Nothing [] []
+
 packageConfig :: FilePath
 packageConfig = "package.yaml"
 
@@ -129,6 +134,7 @@
 , packageConfigMaintainer :: Maybe (List String)
 , packageConfigCopyright :: Maybe (List String)
 , packageConfigLicense :: Maybe String
+, packageConfigTestedWith :: Maybe String
 , packageConfigExtraSourceFiles :: Maybe (List FilePath)
 , packageConfigDataFiles :: Maybe (List FilePath)
 , packageConfigGithub :: Maybe Text
@@ -167,15 +173,8 @@
 
 readPackageConfig :: FilePath -> IO (Either String ([String], Package))
 readPackageConfig file = do
-  config <- decodeFileEither file
-  either (return . Left . errToString) (fmap Right . mkPackage) config
-  where
-    errToString err = file ++ case err of
-      AesonException e -> ": " ++ e
-      InvalidYaml (Just (YamlException s)) -> ": " ++ s
-      InvalidYaml (Just (YamlParseException{..})) -> ":" ++ show yamlLine ++ ":" ++ show yamlColumn ++ ": " ++ yamlProblem ++ " " ++ yamlContext
-        where YamlMark{..} = yamlProblemMark
-      _ -> ": " ++ show err
+  config <- decodeYaml file
+  either (return . Left) (fmap Right . mkPackage) config
 
 data Dependency = Dependency {
   dependencyName :: String
@@ -229,6 +228,7 @@
 , packageCopyright :: [String]
 , packageLicense :: Maybe String
 , packageLicenseFile :: Maybe FilePath
+, packageTestedWith :: Maybe String
 , packageExtraSourceFiles :: [FilePath]
 , packageDataFiles :: [FilePath]
 , packageSourceRepository :: Maybe SourceRepository
@@ -290,7 +290,7 @@
   (dataFilesWarnings, dataFiles) <-
     expandGlobs (fromMaybeList packageConfigDataFiles)
 
-  let package = Package {
+  let pkg = Package {
         packageName = name
       , packageVersion = fromMaybe "0.0.0" packageConfigVersion
       , packageSynopsis = packageConfigSynopsis
@@ -304,6 +304,7 @@
       , packageCopyright = fromMaybeList packageConfigCopyright
       , packageLicense = packageConfigLicense
       , packageLicenseFile = guard licenseFileExists >> Just "LICENSE"
+      , packageTestedWith = packageConfigTestedWith
       , packageExtraSourceFiles = extraSourceFiles
       , packageDataFiles = dataFiles
       , packageSourceRepository = sourceRepository
@@ -321,7 +322,7 @@
         ++ extraSourceFilesWarnings
         ++ dataFilesWarnings
 
-  return (warnings, package)
+  return (warnings, pkg)
   where
     executableSections :: [(String, CaptureUnknownFields (Section ExecutableSection))]
     executableSections = toList packageConfigExecutables
diff --git a/src/Hpack/Run.hs b/src/Hpack/Run.hs
--- a/src/Hpack/Run.hs
+++ b/src/Hpack/Run.hs
@@ -2,12 +2,17 @@
 {-# LANGUAGE QuasiQuotes #-}
 {-# LANGUAGE RecordWildCards #-}
 {-# LANGUAGE ViewPatterns #-}
+{-# LANGUAGE CPP #-}
 module Hpack.Run (
   run
--- exported for testing
 , renderPackage
+, RenderSettings(..)
+, CommaStyle(..)
+, defaultRenderSettings
+#ifdef TEST
 , renderSourceRepository
 , formatDescription
+#endif
 ) where
 
 import           Prelude ()
@@ -27,14 +32,14 @@
 run = do
   mPackage <- readPackageConfig packageConfig
   case mPackage of
-    Right (warnings, package) -> do
-      let cabalFile = packageName package ++ ".cabal"
+    Right (warnings, pkg) -> do
+      let cabalFile = packageName pkg ++ ".cabal"
 
       old <- tryReadFile cabalFile
 
       let alignment = fromMaybe 16 (old >>= sniffAlignment)
           settings = maybe defaultRenderSettings sniffRenderSettings old
-          output = renderPackage settings alignment (maybe [] extractFieldOrderHint old) package
+          output = renderPackage settings alignment (maybe [] extractFieldOrderHint old) pkg
       return (warnings, cabalFile, output)
     Left err -> die err
 
@@ -98,6 +103,7 @@
       , ("copyright", formatList packageCopyright)
       , ("license", packageLicense)
       , ("license-file", packageLicenseFile)
+      , ("tested-with", packageTestedWith)
       , ("build-type", Just "Simple")
       , ("cabal-version", Just ">= 1.10")
       ]
diff --git a/src/Hpack/Util.hs b/src/Hpack/Util.hs
--- a/src/Hpack/Util.hs
+++ b/src/Hpack/Util.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE CPP #-}
 module Hpack.Util (
   List(..)
 , GhcOption
@@ -11,9 +12,9 @@
 , expandGlobs
 , sort
 , lexicographically
-
--- exported for testing
+#ifdef TEST
 , splitField
+#endif
 ) where
 
 import           Control.Applicative
diff --git a/src/Hpack/Yaml.hs b/src/Hpack/Yaml.hs
new file mode 100644
--- /dev/null
+++ b/src/Hpack/Yaml.hs
@@ -0,0 +1,16 @@
+{-# LANGUAGE RecordWildCards #-}
+module Hpack.Yaml where
+
+import           Data.Yaml
+
+decodeYaml :: FromJSON a => FilePath -> IO (Either String a)
+decodeYaml file = do
+  result <- decodeFileEither file
+  return $ either (Left . errToString) Right result
+  where
+    errToString err = file ++ case err of
+      AesonException e -> ": " ++ e
+      InvalidYaml (Just (YamlException s)) -> ": " ++ s
+      InvalidYaml (Just (YamlParseException{..})) -> ":" ++ show yamlLine ++ ":" ++ show yamlColumn ++ ": " ++ yamlProblem ++ " " ++ yamlContext
+        where YamlMark{..} = yamlProblemMark
+      _ -> ": " ++ show err
diff --git a/test/Hpack/ConfigSpec.hs b/test/Hpack/ConfigSpec.hs
--- a/test/Hpack/ConfigSpec.hs
+++ b/test/Hpack/ConfigSpec.hs
@@ -12,14 +12,15 @@
 
 import           Helper
 
-import           Data.Aeson.Types
 import           Data.Aeson.QQ
+import           Data.Aeson.Types
 import           Data.String.Interpolate
 
-import           Hpack.Config
+import           Hpack.Config hiding (package)
+import qualified Hpack.Config as Config
 
 package :: Package
-package = Package "foo" "0.0.0" Nothing Nothing Nothing Nothing Nothing Nothing [] [] [] Nothing Nothing [] [] Nothing Nothing [] []
+package = Config.package "foo" "0.0.0"
 
 executable :: String -> String -> Executable
 executable name main_ = Executable name main_ []
diff --git a/test/Hpack/RunSpec.hs b/test/Hpack/RunSpec.hs
--- a/test/Hpack/RunSpec.hs
+++ b/test/Hpack/RunSpec.hs
@@ -5,7 +5,7 @@
 import           Data.List
 
 import           Hpack.ConfigSpec hiding (spec)
-import           Hpack.Config
+import           Hpack.Config hiding (package)
 import           Hpack.Render
 import           Hpack.Run