ここの Haskell エコシステムにとって非常に新しいものです。hunit をインストールしようとしていますが、実行するcabal install hunitと次のメッセージが表示されます。
Warning: The install command is a part of the legacy v1 style of cabal usage.
Please switch to using either the new project style and the new-install
command or the legacy v1-install alias as new-style projects will become the
default in the next version of cabal-install. Please file a bug if you cannot
replicate a working v1- use case with the new-style commands.
For more information, see: https://wiki.haskell.org/Cabal/NewBuild
cabal: There is no package named 'hunit'. However, the following package name
exists: 'HUnit'.