Fix pattern to only load files under our test directory

Author: carlosantoniodasilva

Rakefile

@@ -6,8 +6,7 @@ task :default => [:test]
 Rake::TestTask.new(:test) do |t|
   t.libs << 'lib'
   t.libs << 'test'
-  dir = File.dirname(__FILE__)
-  t.pattern = "#{dir}/**/*_test.rb"
+  t.pattern = "test/**/*_test.rb"
   t.verbose = true
   t.warning = true
 end