For compatibility with original doctest parser
you cannot write
{-# LANGUAGE MyPreferredExtension #-}
Instead you must write
:set -XMyPreferredExtension
In Literal Haskell files
only \\begin{code} ... \\end{code} blocks are scanned,
but not bird style code blocks.
prop> supports multi-line code,
but both original doctest and haddock do not support it.
IO tests are not supported as doctest examples, so far.
We need a syntactic distinction for IO tests,
because doctest-extract does not employ a type-checker.
We could mark IO tests
with a specific id function, as in ioTest $ runMyTest
or a type annotation, as in runMyTest :: IO ().
Tipps and Tricks
How to disable selected tests?
For focussing on certain tests it can be useful to disable other ones.
We have not implemented a mechanism to disable parts of the test suite
in doctest-extract,
because this would require to implement a way to identify tests.
You can still disable some of the tests
without explicit support by doctest-extraxt.
If you want to disable whole modules,
you may make a copy of the auto-generated Test/Main.hs
and remove the modules that you want to skip.
For disabling all tests on a function
you may turn a Haddock comment into a plain comment
by removing the bar after the opening of the comment.
For disabling individual tests you may prefix >>> and prop>
with an asterisk or the like.
These tricks work best in conjunction with a revision control systen,
such that it always reminds you that there are tests disabled temporarily.
