1 files changed, 16 insertions, 0 deletions
diff --git a/tasks/mrbgem_spec.rake b/tasks/mrbgem_spec.rake
index 7b6751390..2d61d5908 100644
--- a/tasks/mrbgem_spec.rake
+++ b/tasks/mrbgem_spec.rake
@@ -169,6 +169,22 @@ module MRuby
       end
 
     end # Specification
+
+    class List < Array
+      def <<(gem)
+        fail ArgumentError.new("Don't find directory for this GEM") unless gem.respond_to? :dir
+        unless include?(gem)
+          super(gem)
+        else
+          # GEM was already added to this list
+        end
+      end
+
+      # we assume that a gem with the same directory is equal
+      def include?(gem)
+        detect {|g| g.dir == gem.dir }
+      end
+    end # List
   end # Gem
 
   GemBox = Object.new