RSpec was chosen to be used for acceptance tests for many reasons:
* The tests are actually much cleaner now. It is clearer to see what
is being tested, and what is being used for setup.
* Matcher transition will be coming soon. This will really clean up
a lot of the "assert" boilerplate all over. There was a lot of repetition
in this area.
* Shared examples will help greatly for testing common error cases
for many commands.
* The test runner for RSpec is simply much better. Being able to specify
the exact test to run by line, for example, is a great help.
* First test that uses "vagrant up"
* Allow interaction with processes executed during `execute` so that
we can enter input into STDIN and receive data from STDOUT in
real time.
* Fix some issue with `waitpid2`, which actually speeds up all tests
quite a bit.