class Gem::TestCase

def build_rake_in(good=true)
  gem_ruby = Gem.ruby
  Gem.ruby = @@ruby
  env_rake = ENV["rake"]
  rake = (good ? @@good_rake : @@bad_rake)
  ENV["rake"] = rake
  yield rake
ensure
  Gem.ruby = gem_ruby
  if env_rake
    ENV["rake"] = env_rake
  else
    ENV.delete("rake")
  end
end