This is a little output test suit for Haddock. To add a test: 

 1 Create a module in the "tests" directory
 2 Run runtests.hs
   You should now have output/<modulename>.html but the test will always
   pass since there is no reference output to compare with
 3 To add reference output, do
     runhaskell copy.hs <modulename>

Tips:

You can do
  runhaskell copy.hs
to copy all output into reference files

You can do
  runhaskell runtests.hs all
to continue despite a failing test

You can pass extra options to haddock like so
  runhaskell runtests.hs --xhtml all