Rails 2.3.x requires new test_helper

I was getting weird errors like:

.../test/test_helper.rb:11: undefined method `use_instantiated_fixtures=' for Test::Unit::TestCase:Class (NoMethodError)

When trying to run “rake test” on an application that actually had no tests defined, (my goal is to add a few) that was built with rails 2.3.2.

It turns out that in rails 2.3 (?- maybe 2.2, my other applications are at 2.1), the unit test cases are now subclassed from ActiveSupport::TestCase instead of Test::Unit::TestCase.

This matters for both test_helper.rb and the *_test.rb files.