specify mocha version to ensure test not broken

Gemfile

@@ -6,6 +6,7 @@ gem 'rake'
 gem 'fakefs', :require => nil
 gem 'guard'
 gem 'guard-rspec'
+gem 'mocha', '~> 0.12.3'
 
 require 'rbconfig'
 if RbConfig::CONFIG['target_os'] =~ /darwin/i

guard-rails.gemspec

@@ -22,5 +22,5 @@ Gem::Specification.new do |s|
   s.add_dependency 'guard', '>= 0.2.2'
 
   s.add_development_dependency 'rspec', '~> 2.6.0'
-  s.add_development_dependency 'mocha'
+  s.add_development_dependency 'mocha', '~> 0.12.3'
 end