The `brew test` tests were failing as they were unable to include
`test/unit/assertions`. This is because it's a gem and we were setting
the `GEM_HOME` so system gems were being ignored.
While I was there and examining the `$LOAD_PATH`: reduce the number of
things we add there by using `Bundler.with_clean_env` and only adding
`HOMEBREW_LIBRARY_PATH` in the `$LOAD_PATH` if it isn't already there
(which it always is [and has to be] for integration tests).
This also seems to have the side effect of speeding up integration
tests from 1m26s to 1m8s on my machine.
This is the (partially) documented public API for Homebrew.
The main class you should look at is the {Formula} class (and classes linked from there). That's the class that's used to create Homebrew formulae (i.e. package descriptions). Assume anything else you stumble upon is private.