Turn warnings on for AS isolated tests

activesupport/Rakefile

@@ -24,7 +24,7 @@ Rake::TestTask.new { |t|
 task :isolated_test do 
   ruby = File.join(*RbConfig::CONFIG.values_at('bindir', 'RUBY_INSTALL_NAME'))
   Dir['test/**/*_test.rb'].all? do |file|
-    system(ruby, '-Ilib:test', file)
+    system(ruby, '-w', '-Ilib:test', file)
   end or raise "Failures"
 end