Plugins - preload_fixtures
Add to favoritesPreloadFixtures simply preloads ALL your fixtures at the beginning of your test cycle. It forces the system into using transactional fixtures, which you'll need because you're only loading the fixtures once! Make sure to use this plugin only when your database supports transactions.
Usage
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1. Install the plugin
2. Add the following to test/test_helper.rb
PreloadFixtures.preload!
PreloadFixtures.instantiate!(Test::Unit::TestCase)
3. The "fixtures" function in a test is now overloaded to do nothing. All fixtures in the directory will be loaded once and then the tests will be run.

Isn't this the default as of (at least) rails 2.1 ? I see a fixtures :all in my test_helper.rb
This plugin is useful but does break stuff at the moment - notably the ability to specify a your own teardown method in your TestCases. I'm not sure why.