Exploration Through Example

Example-driven development, Agile testing, context-driven testing, Agile programming, Ruby, and other things of interest to Brian Marick
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Wed, 24 Aug 2005

Still more on counterexamples

Due to conversations with Jonathan Kohl and John Mitchell, a bit more on counterexamples.

I now think that what I'm wondering about is team learning. I want to think more about two questions:

  • Say someone comes up with a counterexample, perhaps that one kind of user uses the product really differently. How is that integrated into the mindset of the team? That is, how does it become an example of an extended model of product use? (I fear too often it stays as an awkward, unintegrated counterexample.)

    Take the blocks world example. In Winston's work, he taught a computer to identify arches by giving it examples and counterexamples. (Eugene Wallingford confirms that the counterexamples were necessary.) In that world, an arch was two pillars of blocks with a crosspiece. The counterexamples included, if I remember correctly, arches without a top (just two pillars) and maybe a crosspiece balanced on a single pillar.

    It's fine and necessary for a researcher to teach a computer - or a product owner a development team - about already understood ideas like "arch". But it's even more fine when the process of teaching surprises the teacher with a new, useful, and more expansive understanding of the domain. I want more surprise in the world.

  • Is there a way to give counterexamples elevated importance in the team's routine action? So that it isn't exceptional to integrate them into the domain model?

    One thing testers do is generate counterexamples by, for example, thinking of unexpected patterns of use. What happens when those unexpected patterns reveal bugs? (When, in Bret Pettichord's definition of "bug", the results bug someone.) The bugs may turn into new stories for the team, but in my experience, they're rarely a prompt to sit down and think about larger implications.

    An analogy: that's as if the refactoring step got left out of the TDD loop. It is when the programmer acts to remove duplication and make code intention-revealing that unexpected classes arise. Without the refactoring, the code would stay a mass of confusing special cases.

    Sometimes - as in the Advancer example I cite so compulsively - the unexpected classes reflect back into the domain and become part of the ubiquitous language. So perhaps that reflection is one way to make incorporating counterexamples routine. We tend to think of the relationship between product expert and team as mainly directional, one of master to apprentice: the master teaches the apprentice what she needs to know. Information about the domain flows from the master to the apprentice. There's a conversation, yes, but the apprentice's part in the conversation is to ask questions about the domain, to explain the costs of coping with the domain in a certain way, to suggest cheaper ways of coping - but not to change the expert's understanding of the domain. Perhaps we should expect the latter.

    Put another way: suppose we grant that a project develops its own creole - its own jargon - that allows the domain expert(s) and technical team to work effectively with each other. Something to keep casual track of would be how many nouns and verbs in the creole originated in the code.

## Posted at 08:02 in category /ideas [permalink] [top]

More on video

In response to my note on Jim Shore's video, Chris McMahon points to HermesJMS, an open source tool for managing message queues. He says:

Configuring any such tool is a chore, but the HermesJMS author has included video on how to configure all of the options of the tool: check out the "Demos" links from the left side of the home page for a really elegant use of video to explain complex activity in a sophisticated tool.

I should also mention the video for Ruby on Rails. The speed with which things get done is much more apparent on video than it would be in text.

## Posted at 08:02 in category /misc [permalink] [top]

About Brian Marick
I consult mainly on Agile software development, with a special focus on how testing fits in.

Contact me here: marick@exampler.com.




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Working your way out of the automated GUI testing tarpit
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