[rspec-users] Shared contexts

Andrew Wagner wagner.andrew at gmail.com
Tue Nov 16 13:07:17 EST 2010


Suppose we have this class:

class MarbleMachine
  def insert color
    # process marble of color 'color'
  end

  def press button
    # process a push of the given button
  end

  def output
    # compute a result
  end
end

Let's presume here that the machine takes any number of marbles in any of 8
different colors, and that it has a few different buttons that can be
pressed. The output is highly dependent on what actions you take, in what
order. Obviously, a bit of a silly example, but easier than explaining a
complex, highly data-driven application.

Ok, now let's think about writing some specs. We're really not interested in
trying to specify every possible scenario. But there are a few scenarios
that we know are important. For example, we know that the customer is very
interested in what happens in the state the machine is in after the
sequence:

[:blue_marble, :medium_button, :black_marble, :orange_marble]

What happens if you insert two green marbles after this? What happens if you
insert a yellow marble and press the big purple button? etc.

In addition, the customer is also very interested in what happens if you
push the red button when the machine is in a variety of states.

What I'm trying to get at, here, is that I want to share some complex
contexts across specs while not varying the action I'm specifying. I also
want to vary the action I'm specifying in a number of different contexts
(which is more along the lines of shared examples). I don't really want to
think about it in terms of the state that exists, because that's not useful
from the customer's standpoint. To be sure that things are set up correctly,
we need to be able to say what happened, not just what the state is.

So, how would you organize your specs in a scenario like this?
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