Running tests for acts_as_tree plugin

If I checkout the acts_as_tree plugin from
git://github.com/rails/acts_as_tree.git and try to run its unit tests, I
get a failure:

$ rake
(in /u/home/brian/git/acts_as_tree)
/usr/local/bin/ruby -Ilib:lib
“/usr/local/lib/ruby/gems/1.8/gems/rake-0.8.3/lib/rake/rake_test_loader.rb”
“test/acts_as_tree_test.rb”
/usr/local/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_support/dependencies.rb:276:in
load_missing_constant': uninitialized constant ActiveRecord::Acts (NameError) from /usr/local/lib/ruby/gems/1.8/gems/activesupport-2.1.2/lib/active_support/dependencies.rb:468:inconst_missing’
from ./test/…/init.rb:1
… etc

However, I can make them run if I make a one-line addition to init.rb:

diff --git a/init.rb b/init.rb
index 0901ddb…3e4d07b 100644
— a/init.rb
+++ b/init.rb
@@ -1 +1,2 @@
+require ‘active_record/acts/tree’
ActiveRecord::Base.send :include, ActiveRecord::Acts::Tree

Is there something odd about my environment, or is this an error in the
plugin? I have rails 2.1.2 and rake 0.8.3 gems installed, but I’m
testing acts_as_tree separately, not within a rails project.

Thanks,

Brian C…