my RSpec note

it{ expect{something.save}.to change{ SomethingRelation.count }.by(3) }
it{ expect{something.save!}.to raise_error(StandardError) }

before{ allow_any_instance_of(ClassName).to receive(:a_method).and_return('great!') }
before{ allow_any_instance_of(ClassName).to receive(:a_method).and_raise(StandardError.new("error"))  }
before{ ClassName.any_instance.stub(:a_method).and_return('cool!') }
before{ ClassName.any_instance.stub(:a_method).and_raise('error!') }

bundle exec rspec
bundel exec rspec spec/models/xxxx_spec.rb           ## specify specific file
bundel exec rspec spec/models/xxxx_spec.rb -e status ## specify a test in specific file

rake db:rollback RAILS_ENV=test
rake db:migrate RAILS_ENV=test