diff --git a/Gemfile b/Gemfile
index 0cb99e26..9d71f2a9 100644
--- a/Gemfile
+++ b/Gemfile
@@ -5,5 +5,7 @@ group :development do
   gem "hoe-gemspec"
   gem "rake-compiler"
   gem "yard"
+  gem "minitest"
+  gem "test-unit"
 end
 
diff --git a/ext/opencv/extconf.rb b/ext/opencv/extconf.rb
index 1500fa51..eea35a19 100755
--- a/ext/opencv/extconf.rb
+++ b/ext/opencv/extconf.rb
@@ -11,7 +11,7 @@
 
 require "mkmf"
 
-def cv_version_suffix(incdir)
+def _cv_version_suffix(incdir)
   major, minor, subminor = nil, nil, nil
   open("#{incdir}/opencv2/core/version.hpp", 'r') { |f|
     f.read.lines.each { |line|
@@ -20,15 +20,28 @@ def cv_version_suffix(incdir)
       subminor = $1.to_s if line =~ /\A#define\s+(?:CV_VERSION_MINOR|CV_SUBMINOR_VERSION)\s+(\d+)\s*\Z/
     }
   }
+end
+
+def cv_version_suffix(incdir)
+  major, minor, subminor = _cv_version_suffix(incdir)
   major + minor + subminor
 end
 
+def cv_version_major(incdir)
+  major, minor, subminor = _cv_version_suffix(incdir)
+  major
+end
+
 # Quick fix for 2.0.0
 # @libdir_basename is set to nil and dir_config() sets invalid libdir '${opencv-dir}/' when --with-opencv-dir option passed.
 @libdir_basename ||= 'lib'
 incdir, libdir = dir_config("opencv", "/usr/local/include", "/usr/local/lib")
 dir_config("libxml2", "/usr/include", "/usr/lib")
 
+if cv_version_suffix(incdir) == "3" 
+  raise "not ready for ", cv_version_suffix(incdir), "yet\n"
+end
+
 opencv_headers = ["opencv2/core/core_c.h", "opencv2/core/core.hpp", "opencv2/imgproc/imgproc_c.h",
                   "opencv2/imgproc/imgproc.hpp", "opencv2/video/tracking.hpp", "opencv2/features2d/features2d.hpp",
                   "opencv2/flann/flann.hpp", "opencv2/calib3d/calib3d.hpp", "opencv2/objdetect/objdetect.hpp",
diff --git a/test/test_cvbox2d.rb b/test/test_cvbox2d.rb
index ced01d74..cab2eb7f 100755
--- a/test/test_cvbox2d.rb
+++ b/test/test_cvbox2d.rb
@@ -1,6 +1,6 @@
 #!/usr/bin/env ruby
 # -*- mode: ruby; coding: utf-8 -*-
-require 'test/unit'
+require 'test-unit'
 require 'opencv'
 require File.expand_path(File.dirname(__FILE__)) + '/helper'