add activemodel-mocks and patch

Gemfile

@@ -13,6 +13,7 @@ group :development, :test do
   gem 'ffaker'
   gem 'rails', '~> 4.2.0'
   gem 'rspec-rails', '~> 2.13'
+  gem 'rspec-activemodel-mocks'
 end
 
 gemspec

spec/support/rspec-activemodel-mocks_patch.rb

@@ -0,0 +1,8 @@
+# Manually applied the patch from https://github.com/jdelStrother/rspec-activemodel-mocks/commit/1211c347c5a574739616ccadf4b3b54686f9051f
+if Gem.loaded_specs['rspec-activemodel-mocks'].version.to_s != "1.0.1"
+  raise "RSpec-ActiveModel-Mocks version has changed, please check if the behaviour has already been fixed: https://github.com/rspec/rspec-activemodel-mocks/pull/10
+If so, this patch might be obsolete-"
+end
+RSpec::ActiveModel::Mocks::Mocks::ActiveRecordInstanceMethods.class_eval do
+  alias_method :_read_attribute, :[]
+end