rake test:plugins boots rails twice

I have created a few plugins, and I can run 'rake test' from inside their dirs just fine. But once I am using them in a Rails project, and try 'rake test:plugins', I was getting this weird message from rake, saying that my test_* functions were already defined.
After messing around a bit, I noticed that, when test:plugins is run, Rails will execute the code in config/boot twice.
Here is a simple example:

$ rails temp $ cd temp $ ./script/generate plugin foobar edit config/boot.rb:

 def boot!
  unless booted?
    puts "TEST_STRING!!!"
    preinitialize
    pick_boot.run
  end

nicolae:temp zeh$ rake test:plugins
(in /Users/zeh/temp) TEST_STRING!!!
/opt/local/bin/ruby -I"lib:test" "/opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake/rake_test_loader.rb" "vendor/plugins/foobar/test/foobar_test.rb" TEST_STRING!!!
Loaded suite /opt/local/lib/ruby/gems/1.8/gems/rake-0.8.7/lib/rake/rake_test_loader
Started
. Finished in 0.03464 seconds.

1 tests, 1 assertions, 0 failures, 0 errors

that string will show up twice. the same doesn't happen with other rake tasks, like db:migrate, db:drop:all, test, gem -- nor while running console or server (only once).

I might be mistaken, but I don't think that's the desired behavior.