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

[Andrew Bennetts]

Andrew Bennetts has voted tweak.
Status is now: Conditionally approved
Comment:
See my comments on the list.

For details, see: 
http://bundlebuggy.aaronbentley.com/request/%3C46B8553A.6040604%40warwick.ac.uk%3E