Stories about Software


Implied Acceptance Criteria

I’m on a Scrum team these days, serving as Product Owner, and I was watching developers do functionality demos. This has generally been of the form of them walking me through the happy path, and then me taking it for a test drive and trying to put myself in a user, ‘cleverly’ typing “twenty five” into a text box that clearly wants an integer to see what happens.

Yellow screen of death? Generic error message? Scornful validation message such as “dude, what’s wrong with you?” Helpful validation message such as “your response for how many children you have cannot be a negative number, a decimal, or typeset nonsense?”

Universal Acceptance Criteria?

If what happens isn’t what I think should happen, it’s then off to check out the acceptance criteria/tests. Did it say anything in there about a validation message? Should it have to? Are there things that ought to be “universal acceptance criteria?”

To me, the answer to that question is, “sort of, but I’d prefer to think of them more as default/implied ACs.” And so I started to enumerate them on an internal wiki, kind of as an exercise for myself to see if there were certain things that I think should always be true. Maybe these are like the equivalent of code contracts, but contracts between the developer and the user. Here are some ideas that I came up with:

  • When user supplies invalid input, a message should be shown explaining why the input was not accepted.
  • The way to get back to where you just were should always be available and obvious (e.g. “cancel” button or “back” link or something).
  • Nothing that happens should ever result in a “yellow screen” or whatever equivalent indicates to the user that whatever is going wrong is something you never dreamed of (for production release, anyway — I have no issues with crashes like this in internal or beta tests as part of a “fail early” strategy)
  • If an exception occurs that the user would understand, it is explained to the user (e.g. “The connection to the database was lost.”)
  • There is never a point during the normal course of usage where the user thinks, “should I just, like, wait, or is it frozen?”
  • If it’s possible to prevent the user from doing the wrong thing, the user is prevented from doing the wrong thing (e.g. if user clicks “save” and that’s a long running operation, “save” button is disabled until it’s okay to click again)

Explaining Implied/Default Acceptance Criteria

These are some things that I think ought to be true of your application’s behavior unless there is a good reason to deviate. These are things that I generally think of when I’m working, even if nothing is spelled out explicitly. I think of these and I think of more, depending on the application context (e.g. is this something that should be permission controlled or is this something where the verbiage might be changed later?)

Over the years, I’ve developed a pretty lengthy mental checklist for what I consider good application experience, even without consciously realizing that I’ve done so for the most part. But I think it’s important for us to try to grow this evoked set in our minds as we go.

So what about you? Do you have anything you’d add to this list — any glaring omissions? I’m actually looking to tabulate some of these things into a working document and perhaps expand it to cover other kinds of minimal checklists for various scenarios (such as testing your own code via running the application, finding and fixing a bug, etc). Perhaps when I get it more fleshed out at some point, I’ll revisit and post again, but either way, I’d be interested to hear what you consider to be table stakes/minimum standards for how your applications interact with users.

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