Review: [MERGE] Convert test.blackbox.test_c* to use internals where appropriate

[Ian Clatworthy]

Ian Clatworthy has voted tweak.
Status is now: Conditionally approved
Comment:
Some indenting nits in test_cat.py, otherwise all good. Not merged yet 
so I'll do it now.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C1188468535.29725.8.camel%40lapbert%3E