Unit Tests Are Still a Waste of Time

Per a recent Dr. Dobbs article, the only reason to write unit tests is as a “convenience … to track down bugs faster.” If that’s the only value proposition, then I must agree with the author that writing unit tests is a “luxury” that only infrequently makes sense.

You’d be far better off investing the time in improving your integration tests or (much better) bolstering the tests that demonstrate customer acceptance criteria. They run much more slowly, but provide more value than writing unit tests after you code: They not only help prevent you from creating defects in the system, they can also be a key negotiation point, and they can act as living documentation on the behaviors your system supports.

Fortunately, writing tests first can create myriad other benefits that outweigh their cost: reduced system size, tests that improve developer understanding of system behaviors, more decoupled/cohesive designs, cleaner code, and the ability to change code safely and rapidly as it needs to be changed. Yes, there’s some churn along the way, but it’s usually mild (and milder as the quality of design improves). These benefits are why I’ve done TDD for a dozen years now, having witnessed some fantastic successes along the way.

You Don’t Build Stories

I recently responded to a poster at JavaRanch who was asking about how stories are used in agile. I think a lot of people use the word “story” improperly–they use it in the sense that a story is a feature. “I built 10 stories into the product.” No, a story is a discussion around a feature. A story is also not a card.

While this may seem like a nit that I’m picking, I believe misuse of the word “story” has led to unfortunate insistences, such as rigid formats for cards that capture feature conversations (and I’m going to stop calling these cards “story cards,” which isn’t quite as bad a term, but it does help reinforce the wrong things).

(Most of the rest of this post is taken directly from the exchange on JavaRanch.)

“Story cards” are simply placeholders, or tools. The word “story” is the important thing here. A story is something we tell people; the card is simply a reminder, a summary of that oral storytelling. A card is a convenient medium. I suppose I’m thankful I don’t hear about “story whiteboards.”

Story cards (I tried… it’s not easy!) are not artifacts! Once you complete work on building a feature, the card is meaningless. You might think you could use it to track what had been done in a given iteration, but a 5-word summary of a several-day conversation (between customer and developers and other folks) scribbled on a card will not likely be meaningful to anyone six months down the road.

Instead, we get rid of the conversation piece, and replace it with something that documents how the system behaves once that new feature is in place. The best form for that document is a series of well-designed acceptance tests that anyone can easily read and understand. (See our Agile in a Flash card on Acceptance Test Design Principles for a definition of well-designed.)

Acceptance tests are the closest analogs to use cases (a tool popularized almost 20 years ago now), but with slightly differing granularities. The name of an acceptance test can map to the goal, or name, of a use case; it can also map to a much smaller slice of functionality. This is because features in agile are intended to be very small, taking only a day or so to complete. So someone might tell a story: “allow users to filter sort results by age.” That’s likely not an entire use case, it’s an alternate path on a larger use case.

Otherwise, the focus is the same: Jacobson said you could produce user guides and documentation from well-written use cases. The same can hold true for acceptance tests (with a little assembly work), which have the vastly superior quality of eternal accuracy: As long as all your acceptance tests pass, you know that they describe how the system works.

Stories, on the other hand, are just conversations, and the memory of all conversations eventually fades from memory. The cards act as great tools while the story is in progress–they help us track things and remind us what we were talking about, but other than that, we should just recycle the cards once we deliver the corresponding features.

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