def test_gettopdir():

       tmp = py.test.ensuretemp("topdir")

       assert gettopdir([tmp]) == tmp

->     topdir =gettopdir([tmp.join("hello"), tmp.join("world")])

       assert topdir == tmp 

   def gettopdir(args): 

       """ return the top directory for the given paths.

           if the common base dir resides in a python package 

           parent directory of the root package is returned. 

       """

       args = [py.path.local(arg) for arg in args]

->     p = reduce(py.path.local.common, args)

       assert p, "cannot determine common basedir of %s" %(args,)

       pkgdir = p.pypkgpath()

       if pkgdir is None:

           return p

       else:

           return pkgdir.dirpath()