Require at least minitest >= 4.

thedarkone · thedarkone · commit c1ce62ea6f03 · 2014-04-12T19:47:24.000+02:00
diff --git a/thread_safe.gemspec b/thread_safe.gemspec
@@ -21,5 +21,5 @@ Gem::Specification.new do |gem|
 
   gem.add_development_dependency 'atomic', ['>= 1.1.7', '< 2']
   gem.add_development_dependency 'rake'
-  gem.add_development_dependency 'minitest'
+  gem.add_development_dependency 'minitest', '>= 4'
 end
