attr_readonly

To test if an attribute is defined readonly:

class MyModel < ActiveRecord::Base
attr_readonly :important_type_thingie
end

#RSpec
describe MyModel do

its('class.readonly_attributes') { should include "important_type_thingie" }

it "should not update the thingie" do m = create :my_model, :important_type_thingie => 'foo' m.update_attributes :important_type_thingie => 'bar' m.reload.important_type_thingie.should eql 'foo' end end