'Test preferred providers of virtual packages are
applied correctly'

def test_preferred_providers(self):

    update_packages('all', 'providers', {'mpi': ['mpich']})
    spec = concretize('mpileaks')
    assert ('mpich' in spec)
    update_packages('all', 'providers', {'mpi': ['zmpi']})
    spec = concretize('mpileaks')
    assert ('zmpi' in spec)
