I wanted to force an error condition in my cucumber tests, but the code ran through a DelayedJob, so I couldn’t redefine the code running under the .delay chain, because the DelayedJob worker will reload the normal code base for its processing. I finally realized that simply patching the delay instance method to return self for the class in question would bypass the delayed job.

def force_query_error
  ObjectDelayed.class_eval do
    alias :old_delay :delay
    alias :old_query :query

    def delay
      self
    end

    def query
      raise 'monkey'
    end
  end
end

def restore_query
  ObjectDelayed.class_eval do
    remove_method :query
    remove_method :delay
    alias :query :old_query
    alias :delay :old_delay
  end
end

This is not to be confused will actually allowing DelayedJob to do its thing:

When(/^I wait for processing of jobs$/) do
  Delayed::Worker.new(:quiet => false).work_off
  Timeout::timeout(10) do
    until Delayed::Job.count == 0 do
    end
  end
end