Clear cache at beginning of unit tests.

test/test_helper.rb

@@ -1,6 +1,7 @@
 ENV["RAILS_ENV"] = "test"
 require File.expand_path('../../config/environment', __FILE__)
 require 'rails/test_help'
+require 'cache'
 require 'simplecov'
 require 'simplecov-rcov'
 
@@ -16,6 +17,9 @@ class ActiveSupport::TestCase
   # disable transactions
   self.use_transactional_fixtures = false
 
+  # clear cache
+  Cache.clear
+
   # load seeds
   load "#{Rails.root}/db/seeds.rb"