diff --git a/Gemfile b/Gemfile
index b3b89451..6a781f5e 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,9 +1,10 @@
-source "https://rubygems.org"
+source 'https://rubygems.org'
 gemspec
 
 group :test do
-  gem "rake", ">= 0.8.7"
-  gem "simplecov"
+  gem 'rake', '>= 0.8.7'
+  gem 'simplecov'
+  gem 'minitest'
 end
 
 group :profile do
diff --git a/test/tc_helper.rb b/test/tc_helper.rb
index af40a1e4..373b04c6 100644
--- a/test/tc_helper.rb
+++ b/test/tc_helper.rb
@@ -4,7 +4,7 @@
   add_filter "/test/"
   add_filter "/vendor/"
 end
-
+gem 'minitest'
 require 'test/unit'
 require "timecop"
 require "axlsx.rb"