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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Mon, 05 Apr 2004

Big visible charts

A blog about Big Visible Charts (via Jason Yip).

## Posted at 17:14 in category /agile [permalink] [top]

Poke-inviting code

Michael Feathers:

You think your design is good? Pick a class, any class, and try to instantiate it in a test harness. I used to think that my earlier designs were good until I started to apply that test. We can talk about coupling and encapsulation and all those nice pretty things, but put your money where your mouth is. Can you make this class work outside the application? Can you get it to the point where you can tinker with it, in real time, build it alone in less than a second, and add tests to find out what it really does in certain situations. Not what you think might happen, not what you hope might happen, but what it really does?

That made me think: wouldn't it be nice to be able to point at a class (or some similar unit) and tell it, "You! Make me an object that I can poke at." It would create representative objects (or mocks) that it depended on, then sit there waiting for you to send messages to it via the interpreter.

Somehow, this seems different to me than running the unit tests under a debugger, hitting a breakpoint sometime after the setup method, then poking away. It puts the responsibility for comprehensibility exactly in the code, not one step removed. (Something like the difference between explaining code with a comment and making the code intention-revealing.)

Of course, you'd want the interpreter to be able to generate a unit test from your poking. Any such test would need some cleaning up. But, perhaps a generator that tried to filter out unneeded commands (assuming cooperation from the programmer about side-effects) could make that effort reasonable. Anyone want a Masters' project?

Even if this idea is dumb, maybe there's something to the notion of code that goes out of its way to be explored. Is that different from simply being decoupled? simply being well tested?

## Posted at 09:19 in category /coding [permalink] [top]