Perf: refactor _assign method to avoid inject and defining unneeded local var.

Signed-off-by: Santiago Pastorino <santiago@wyeworks.com>

actionpack/lib/action_view/test_case.rb

@@ -189,11 +189,7 @@ module ActionView
       end
 
       def _assigns
-        _instance_variables.inject({}) do |hash, var|
-          name = var[1..-1].to_sym
-          hash[name] = instance_variable_get(var)
-          hash
-        end
+        _instance_variables.map { |var| [ var[1..-1].to_sym, instance_variable_get(var)] }
       end
 
       def _routes