Example of using the CanCan language described in https://gist.github.com/1509779

report_ability.rb

class Ability
  ReportAbility = AbilityBuilder.new do
    def build
      can :update_content, Report do |report|
        report.being_edited_by?(user)
      end
      can :check_in_report, Report do |report|
        report.being_edited_by?(user)
      end
    end
  end
end

report_ablity_spec.rb

require 'spec_helper'

# ...

class Ability
  describe ReportAbility do
    let(:user) { mock(User) }
    let(:report) { Report.make }

    subject { Ability.build(user, Ability::ReportAbility) }

    stub_from_metadata :user

    context "admin user", user: { admin?: true } do
      stub_from_metadata :report

      context "current editor of a report", report: { being_edited_by?: true } do
        specify {
          report.should_receive(:being_edited_by?).with(user)
          subject.can? :update_content, report
        }

        it { should be_able_to(:update_content, report) }
        it { should be_able_to(:check_in_report, report) }
      end

      context "not current editor of a report", report: { being_edited_by?: false } do
        specify {
          report.should_receive(:being_edited_by?).with(user)
          subject.can? :update_content, report
        }

        it { should_not be_able_to(:update_content, report) }
        it { should_not be_able_to(:check_in_report, report) }
      end
    end
  end
end