test "don't do unnecessary work for no change" do

  # let's assume that there's an enqueue(evt) method which pulls an event into the
  # processing pipeline, and that the enqueue method in turn calls a process(evt) method

  # let's further assume that if an event has an attribute, once processed, we don't want
  # to process it again for the same attribute value. so evt(attr:5), evt(attr:5), evt(attr:6) would
  # generate two process() calls, not three.

  pipeline = Pipeline.new() # or whatever
  spy = mock_method(pipeline.process) # maybe this

  # enqueue our first event
  evt1 = Event.new(attr: 5)
  pipeline.enqueue(evt1)
  assert pipeline.queue.length == 1
  # or
  assert spy.times_called == 1

  # enqueue our second, duplicate event
  dupe_evt1 = Event.new(attr: 5)
  pipeline.enqueue(dup_evt1)
  assert pipeline.queue.length == 1 # dup is discarded
  # or
  assert spy.times_called == 1

  # enqueue our third, unique event
  evt2 = Event.new(attr: 6)
  pipeline.enqueue(evt2)
  assert pipeline.queue.length == 2 # new event is enqueued
  # or
  assert spy.times_called == 2
end