diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -37,7 +37,7 @@
 
 We provide the above properties to FitSpec in the following program:
 
-    import FitSpec
+    import Test.FitSpec
     import Data.List
 
     properties sort =
@@ -139,9 +139,9 @@
 
 
 [Listable]:    https://hackage.haskell.org/package/leancheck/docs/Test-LeanCheck.html#t:Listable
-[Mutable]:     https://hackage.haskell.org/package/fitspec/docs/FitSpec.html#t:Mutable
-[ShowMutable]: https://hackage.haskell.org/package/fitspec/docs/FitSpec.html#t:ShowMutable
-[FitSpec API]: https://hackage.haskell.org/package/fitspec/docs/FitSpec.html
+[Mutable]:     https://hackage.haskell.org/package/fitspec/docs/Test-FitSpec.html#t:Mutable
+[ShowMutable]: https://hackage.haskell.org/package/fitspec/docs/Test-FitSpec.html#t:ShowMutable
+[FitSpec API]: https://hackage.haskell.org/package/fitspec/docs/Test-FitSpec.html
 
 [leancheck]: https://hackage.haskell.org/package/leancheck
 [cmdargs]:   https://hackage.haskell.org/package/cmdargs
diff --git a/TODO.md b/TODO.md
--- a/TODO.md
+++ b/TODO.md
@@ -6,6 +6,9 @@
 
 * (?) announce on mailing list (wait for Haddock to be ready)
 
+* parameterize number of tests in test programs and add slow-test target
+
+* add diff test for IO functions (diff w/ model output and exit status)
 
 documentation
 -------------
diff --git a/doc/tutorial-property-creation.md b/doc/tutorial-property-creation.md
--- a/doc/tutorial-property-creation.md
+++ b/doc/tutorial-property-creation.md
@@ -8,7 +8,7 @@
 
 We first import what is needed:
 
-	import FitSpec
+	import Test.FitSpec
 	import Data.List (sort)
 
 
diff --git a/fitspec.cabal b/fitspec.cabal
--- a/fitspec.cabal
+++ b/fitspec.cabal
@@ -1,5 +1,5 @@
 name:                fitspec
-version:             0.3.0
+version:             0.3.1
 synopsis:            refining property sets for testing Haskell programs
 description:
   FitSpec provides automated assistance in the task of refining test properties
@@ -38,7 +38,7 @@
 source-repository this
   type:            git
   location:        https://github.com/rudymatela/fitspec
-  tag:             v0.3.0
+  tag:             v0.3.1
 
 
 library
diff --git a/src/Test/FitSpec.hs b/src/Test/FitSpec.hs
--- a/src/Test/FitSpec.hs
+++ b/src/Test/FitSpec.hs
@@ -1,4 +1,4 @@
--- | FitSpec: refining property-sets for functional testing
+-- | __ FitSpec: refining property-sets for functional testing __
 --
 -- FitSpec provides automated assistance in the task of refining test properties
 -- for Haskell functions.  FitSpec tests mutant variations of functions under test
@@ -14,7 +14,7 @@
 --
 -- Example, refining a @sort@ specification:
 --
--- > import FitSpec
+-- > import Test.FitSpec
 -- > import Data.List (sort)
 -- >
 -- > properties sort =
@@ -34,6 +34,7 @@
 -- >                      , timeout  = 0
 -- >                      }
 -- >                 (sort::[Word2]->[Word2])
+-- >                 properties
 --
 -- The above program reports the following:
 --
diff --git a/src/Test/FitSpec/Derive.hs b/src/Test/FitSpec/Derive.hs
--- a/src/Test/FitSpec/Derive.hs
+++ b/src/Test/FitSpec/Derive.hs
@@ -1,11 +1,14 @@
--- | Experimental module for deriving Mutable instances
+-- | Experimental module for deriving 'Mutable' and 'ShowMutable' instances
 --
 -- Needs GHC and Template Haskell
 -- (tested on GHC 7.4, 7.6, 7.8, 7.10 and 8.0)
 --
--- Despite Mutable instances being actually very simple, this module can be
--- used to derive those.  However, it will not work on all cases: when that
--- happens, you should write your instances manually.
+-- Despite 'Mutable' instances being actually very simple to write manually,
+-- this module can be used to derive those instances automatically.
+-- However, it will not work on all cases:
+-- when that happens, you should write your instances manually.
+--
+-- If FitSpec does not compile under later GHCs, this module is probably the culprit.
 {-# LANGUAGE TemplateHaskell, CPP #-}
 module Test.FitSpec.Derive
   ( deriveMutable
@@ -36,7 +39,33 @@
     then return []
     else deriveListable t
 
--- | Derives a Mutable instance for a given type 'Name'.
+-- | Derives 'Mutable', 'ShowMutable' and (optionally) 'Listable' instances
+--   for a given type 'Name'.
+--
+-- Consider the following @Stack@ datatype:
+--
+-- > data Stack a = Stack a (Stack a) | Empty
+--
+-- Writing
+--
+-- > deriveMutable ''Stack
+--
+-- will automatically derive the following
+-- 'Listable', 'Mutable' and 'ShowMutable' instances:
+--
+-- > instance Listable a => Listable (Stack a) where
+-- >   tiers = cons2 Stack \/ cons0 Empty
+-- >
+-- > instance (Eq a, Listable a) => Mutable a
+-- >   where mutiers = mutiersEq
+-- >
+-- > instance (Eq a, Show a) => ShowMutable a
+-- >   where mutantS = mutantSEq
+--
+-- If a 'Listable' instance already exists, it is not derived.
+-- (cf.: 'deriveListable')
+--
+-- Needs the @TemplateHaskell@ extension.
 deriveMutable :: Name -> DecsQ
 deriveMutable = deriveMutableE []
 
@@ -54,6 +83,8 @@
       cd <- canDeriveMutable t
       unless cd (fail $ "Unable to derive Mutable " ++ show t)
       liftM2 (++) (deriveListableIfNeeded t) (reallyDeriveMutable cs t)
+-- TODO: document deriveMutableE with an example
+-- TODO: create deriveListableE on LeanCheck?
 
 -- | Checks whether it is possible to derive a Mutable instance.
 canDeriveMutable :: Name -> Q Bool
diff --git a/src/Test/FitSpec/Dot.hs b/src/Test/FitSpec/Dot.hs
--- a/src/Test/FitSpec/Dot.hs
+++ b/src/Test/FitSpec/Dot.hs
@@ -1,4 +1,5 @@
--- | Generate dotfiles (graphviz)
+-- | Experimental module to generate dotfiles (for graphviz) with implications
+--   between property sub-sets.
 module Test.FitSpec.Dot where
 
 import Test.FitSpec
diff --git a/src/Test/FitSpec/Engine.hs b/src/Test/FitSpec/Engine.hs
--- a/src/Test/FitSpec/Engine.hs
+++ b/src/Test/FitSpec/Engine.hs
@@ -215,7 +215,7 @@
                        . transpose
                        . map (compositions . pmap)
 
--- | 'nSurv' @props fs@ returns the number of values that match
+-- | @nSurv props fs@ returns the number of values that match
 --   compositions of properties on the property map.
 --
 -- * @props@ should be a function from a value to a list of properties that
@@ -228,6 +228,8 @@
 --
 -- This function is otherwise unused in this file.  It is just a simpler
 -- version of 'pssurv' to serve as documentation.
+--
+-- It is also not exported!
 nSurv :: (a -> [Bool]) -> [a] -> [Int]
 nSurv props = map (count id)
             . transpose
diff --git a/src/Test/FitSpec/Mutable.hs b/src/Test/FitSpec/Mutable.hs
--- a/src/Test/FitSpec/Mutable.hs
+++ b/src/Test/FitSpec/Mutable.hs
@@ -37,7 +37,7 @@
 --
 -- > tail mutiers
 --
--- Given that the underlying 'Listable' enumeration has no repetitions
+-- Given that the underlying 'Listable' enumeration has no repetitions,
 -- parametric instances defined in this file will have no repeated mutants.
 class Mutable a where
   mutiers :: a -> [[a]]
diff --git a/src/Test/FitSpec/Mutable/Tuples.hs b/src/Test/FitSpec/Mutable/Tuples.hs
--- a/src/Test/FitSpec/Mutable/Tuples.hs
+++ b/src/Test/FitSpec/Mutable/Tuples.hs
@@ -1,7 +1,11 @@
 -- | Mutable instances: septuples up to 12-tuples
 --
--- This is part of a Hack that allows those instances to be hidden from Haddock.
+-- This is partly a Hack that allows those instances to be hidden from Haddock.
 -- Otherwise Haddock documentation will look very ugly.
+-- It also makes "Test.FitSpec.ShowMutable" more readable.
+--
+-- This module is already exported by "Test.FitSpec",
+-- so it is not needed to import this explictly.
 module Test.FitSpec.Mutable.Tuples () where
 
 import Test.FitSpec.Mutable
diff --git a/src/Test/FitSpec/PrettyPrint.hs b/src/Test/FitSpec/PrettyPrint.hs
--- a/src/Test/FitSpec/PrettyPrint.hs
+++ b/src/Test/FitSpec/PrettyPrint.hs
@@ -1,7 +1,4 @@
--- | Poor man's pretty printing library
---
--- This module has somewhat inefficient implementations that could be improved
--- in the future.  i.e.: heavy use of '(++)'.
+-- | A very simple pretty printing library used to generate 'Test.FitSpec' reports.
 module Test.FitSpec.PrettyPrint
   ( beside
   , above
@@ -13,6 +10,7 @@
   , headToUpper
   )
 where
+-- TODO: Fix somewhat inefficient implementations, i.e.: heavy use of '(++)'.
 
 import Data.List (intercalate,transpose,isSuffixOf)
 import Data.Char (toUpper)
diff --git a/src/Test/FitSpec/Report.hs b/src/Test/FitSpec/Report.hs
--- a/src/Test/FitSpec/Report.hs
+++ b/src/Test/FitSpec/Report.hs
@@ -1,3 +1,4 @@
+-- | Generate 'Test.FitSpec' reports.
 module Test.FitSpec.Report
   ( report
   , reportWith
diff --git a/src/Test/FitSpec/ShowMutable.hs b/src/Test/FitSpec/ShowMutable.hs
--- a/src/Test/FitSpec/ShowMutable.hs
+++ b/src/Test/FitSpec/ShowMutable.hs
@@ -161,7 +161,7 @@
 isFunction (Function _) = True
 isFunction _            = False
 
--- | Flatten a MutantS by merging nested 'Function's.
+-- Flatten a MutantS by merging nested 'Function's.
 flatten :: MutantS -> MutantS
 flatten (Tuple ms) = Tuple $ map flatten ms
 flatten (Function [([],s)])  = flatten s
@@ -191,7 +191,7 @@
         show1 _  m             = showMutantS m
 showMutantSAsTuple ns m = showMutantSAsTuple ns (Tuple [m])
 
--- | Show top-level (maybe tuple) named 'MutantS' as a bindings.
+-- Show top-level (maybe tuple) named 'MutantS' as a bindings.
 -- In general, you want to 'flatten' the 'MutantS' before applying this
 -- function.
 showMutantSBindings :: Bool -> [String] -> MutantS -> String
diff --git a/src/Test/FitSpec/ShowMutable/Tuples.hs b/src/Test/FitSpec/ShowMutable/Tuples.hs
--- a/src/Test/FitSpec/ShowMutable/Tuples.hs
+++ b/src/Test/FitSpec/ShowMutable/Tuples.hs
@@ -1,7 +1,8 @@
 -- | ShowMutable instances: septuples up to 12-tuples
 --
--- This is part of a Hack that allows those instances to be hidden from Haddock.
+-- This is partly a Hack that allows those instances to be hidden from Haddock.
 -- Otherwise Haddock documentation will look very ugly.
+-- It also makes "Test.FitSpec.ShowMutable" more readable.
 module Test.FitSpec.ShowMutable.Tuples () where
 
 import Test.FitSpec.ShowMutable
diff --git a/src/Test/FitSpec/TestTypes.hs b/src/Test/FitSpec/TestTypes.hs
--- a/src/Test/FitSpec/TestTypes.hs
+++ b/src/Test/FitSpec/TestTypes.hs
@@ -3,7 +3,7 @@
 -- 'Int2', 'Int3', 'Int4',
 -- 'UInt2', 'UInt3', 'UInt4'.
 --
--- This module basically re-exports LeanCheck's Test.Types module
+-- This module re-exports "Test.LeanCheck.Utils.Types" module
 -- and defines 'Mutable' and 'ShowMutable' instances for the types
 -- defined there.
 module Test.FitSpec.TestTypes (module Test.LeanCheck.Utils.Types) where