$ git clone https://github.com/hspec/hspec-example
$ cd hspec-example/
$ cabal install --only-dependencies --enable-tests                                                 
$ hdevtools check src/Data/String/Strip.hs 
$ hdevtools check test/Data/String/StripSpec.hs                                                 
/home/sol/sandbox/haskell/hspec-example/test/Data/String/StripSpec.hs:3:8:
    Could not find module ‘Test.Hspec’
    It is a member of the hidden package ‘hspec-2.1.2’.
    Perhaps you need to add ‘hspec’ to the build-depends in your .cabal file.
    Use -v to see a list of the files searched for.