If you haven't looked into Shoulda, maybe you should. It's a plugin (and now gem) that works "on top of" Test::Unit. It truly does make it "easy to write elegant, understandable, and maintainable tests".

The following are a few Shoulda macros that I use for the plugins acts_as_ferret, acts_as_taggable_on_steroids, and acts_as_list. I recommend creating a file 'test/shoulda_macros/plugins.rb', and placing these macros in there. For example:

class Test::Unit::TestCase

# Shoulda macros here

end

Acts As Ferret

  def self.should_act_as_ferret(*fields)
    klass = self.name.gsub(/Test$/, '').constantize

    should "include ActsAsFerret methods" do
      assert klass.extended_by.include?(ActsAsFerret::ClassMethods)
      assert klass.include?(ActsAsFerret::InstanceMethods)
      assert klass.include?(ActsAsFerret::MoreLikeThis::InstanceMethods)
      assert klass.include?(ActsAsFerret::ResultAttributes)
    end

    fields.each do |f|
      should "create an index for field named #{f}" do
        assert klass.aaf_configuration[:fields].include?(f)
      end
    end
  end

Use it like:

should_act_as_ferret :any, :fields, :i_may, :have, :specified

Acts As Taggable On Steroids

  def self.should_act_as_taggable_on_steroids
    klass = self.name.gsub(/Test$/, '').constantize

    should "include ActsAsTaggableOnSteroids methods" do
      assert klass.extended_by.include?(ActiveRecord::Acts::Taggable::ClassMethods)
      assert klass.extended_by.include?(ActiveRecord::Acts::Taggable::SingletonMethods)
      assert klass.include?(ActiveRecord::Acts::Taggable::InstanceMethods)
    end

    should_have_many :taggings, :tags
  end

Acts As List

  def self.should_act_as_list
    klass = self.name.gsub(/Test$/, '').constantize

    context "To support acts_as_list" do
      should_have_db_column('position', :type => :integer)
    end

    should "include ActsAsList methods" do
      assert klass.include?(ActiveRecord::Acts::List::InstanceMethods)
    end

    should_have_instance_methods :acts_as_list_class, :position_column, :scope_condition
  end

Note: These tests are quite basic. Except for checking the fields on acts_as_ferret, there isn't any testing of each plugin's options.

These macros are available at http://github.com/mileszs/shoulda_macros. You can find more macros at the Shoulda wiki on GitHub, http://github.com/thoughtbot/shoulda/wikis/example-macros. If you write some of your own shoulda macros, you should link to them on the wiki as well.