Allow for frozen string pragma in generated files.

railties/test/isolation/abstract_unit.rb

@@ -224,8 +224,8 @@ def engine(name)
       FileUtils.mkdir_p(dir)
 
       app = File.readlines("#{app_path}/config/application.rb")
-      app.insert(2, "$:.unshift(\"#{dir}/lib\")")
-      app.insert(3, "require #{name.inspect}")
+      app.insert(4, "$:.unshift(\"#{dir}/lib\")")
+      app.insert(5, "require #{name.inspect}")
 
       File.open("#{app_path}/config/application.rb", "r+") do |f|
         f.puts app