Prevent a redefinition warning when the real Rails.root appears

tools/test.rb

@@ -7,11 +7,12 @@
 require "rails/test_unit/line_filtering"
 require "active_support/test_case"
 
-module Rails
+class << Rails
   # Necessary to get rerun-snippts working.
-  def self.root
+  def root
     @root ||= Pathname.new(COMPONENT_ROOT)
   end
+  alias __root root
 end
 
 ActiveSupport::TestCase.extend Rails::LineFiltering