diff --git a/Gemfile b/Gemfile
index b2b1830..bb0c7b0 100644
--- a/Gemfile
+++ b/Gemfile
@@ -12,4 +12,5 @@ group :development do
   gem "jeweler", ">= 1.5.0.pre6"
   gem "rcov", ">= 0"
   gem "test-construct"
+  gem "ruby-debug"
 end
diff --git a/Gemfile.lock b/Gemfile.lock
index 517dcb5..36fab0c 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,12 +1,14 @@
 GEM
   remote: http://rubygems.org/
   specs:
+    columnize (0.3.2)
     diff-lcs (1.1.2)
     git (1.2.5)
     jeweler (1.5.0.pre6)
       bundler (~> 1.0.0)
       git (>= 1.2.5)
       rake
+    linecache (0.43)
     rake (0.8.7)
     rcov (0.9.8)
     rspec (2.1.0)
@@ -17,6 +19,11 @@ GEM
     rspec-expectations (2.1.0)
       diff-lcs (~> 1.1.2)
     rspec-mocks (2.1.0)
+    ruby-debug (0.10.4)
+      columnize (>= 0.1)
+      ruby-debug-base (~> 0.10.4.0)
+    ruby-debug-base (0.10.4)
+      linecache (>= 0.3)
     test-construct (1.2.0)
     thor (0.14.0)
 
@@ -29,5 +36,6 @@ DEPENDENCIES
   rake
   rcov
   rspec (~> 2.1.0)
+  ruby-debug
   test-construct
   thor (>= 0.14.0)