I use homebrew to manage installations of things like Lua, node, mysql, redis, vim, and more on OSX; I find brew essential to setting up and maintaining a dev environment. It has a ton of packages available and makes it super easy to stay up to date with the latest packages.

busted relies on a package called luafilesystem for directory traversal; however, lfs relies on Lua 5.1.x. The version in homebrew is 5.2. Switching is as easy as:

brew versions lua

which returns

5.2.1    git checkout 894f668 /usr/local/Library/Formula/lua.rb
5.1.4    git checkout 7e5bc89 /usr/local/Library/Formula/lua.rb

so I can

brew switch lua 5.1.4

And use 5.1.4 instead of 5.2.1, allowing me to use busted (and test lfs fixes in 5.2!) This works, in theory, with any brew package.