Stick with a working version of mocha

mocha 0.12.2 is known not to work with test/unit:
freerange/mocha#94

Pinning the version of mocha until this is resolved

Gemfile

@@ -19,7 +19,7 @@ group :test do
   # Shoulda doesn't work nice on 1.9.3 and seems to need test-unit explicitely…
   gem 'test-unit', :platforms => [:mri_19]
   gem 'edavis10-object_daddy', :require => 'object_daddy'
-  gem 'mocha'
+  gem 'mocha', '0.12.1'
   gem 'capybara'
 end