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GitHub User: derekprior
Check out this fork of TableBuilder if you're still looking for something like this. It's been gemified so it's simple to use with bundler and won't result in any deprecation warnings with Rails 3.2
It's worth noting that older versions of RubyGems will report an invalid gemspec for rails 3.2.0. You can upgrade RubyGems to address this (gem update --system) or you can wait for 3.2.1, which will fix this. Details here.
gem update --system
I worry that approaching zsh like this will be like approaching vim via Janus. When I was a Janus user I couldn't tell you what was a feature of Janus' configuration or plugins and what was a native feature of vim. It wasn't until I started my own vim configuration from scratch that I really started to understand what was going on.
In my experience, most of the slowness comes in loading the rails environment for every new test run. You can avoid this with spork. Spork will load your environment once then reload only what it needs for subsequent test runs. To me, it's a must for test driven development with rails.
In addition, you may be able to speed up the tests themselves by eliminating db calls. Ask yourself if you really need a persisted record for your test or if something in memory will do. In most cases, an in memory object with stubs for any associations will be fine for unit tests. Mocking is very powerful and helps you test your code in isolation.