diff --git a/suo.gemspec b/suo.gemspec
index 5a80947..027b35b 100644
--- a/suo.gemspec
+++ b/suo.gemspec
@@ -27,4 +27,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "bundler", "~> 1.5"
   spec.add_development_dependency "rake", "~> 10.0"
   spec.add_development_dependency "rubocop", "~> 0.30.0"
+  spec.add_development_dependency "minitest", "~> 5.5.0"
 end