better test harness

[tzz]

Suggestions from @bheilman and @ph1l

• allow test path override
• set up test directory and clean it up afterwards
• check file contents
• check file existence/non-existence and attributes
• not a QA run, always simulated
• start working on a QA harness in addition to a test harness (maybe a new run environment class)
• consider using xunit test harness

[tzz]

I haven't been able to find a good Perl or other language module to do the full harness (create, clean up, check files). I can write my own but wanted to check if anyone knows.