如何编写Rails3 rake任务以运行单个单元或功能测试

$ ruby -Itest test/unit/post_test.rb -n test_the_truth

Loaded suite unit/post_test
Started
.
Finished in 0.023513 seconds.

1 tests, 1 assertions, 0 failures, 0 errors

task :tester => :environment do
  `cd #{Rails.root} && ruby -Itest test/unit/post_test.rb -n test_the_truth`
end