The current description test took a hand crafted Manifest. Since
the internal `Manifest` representation and the format (version 1)
representation are becoming more and more different, it might
soon not be possible to go from `Manifest` to the format specific
description unless it was previously loaded and thus an internal
mapping table can aid the serialization. Thus the description
test is re-worked to load a manifest and then describe it and
compare that the result is the same.
Also rename the test from `test_pipeline` to `test_describe`
as this is a better description of the test.
105670e3f9