Negative Scenarios in BDD

One problem I hear repeatedly from people is that they can’t find a good place to start talking about scenarios.

An easy trick is to find the person who fought to get the budget for the project (the primary stakeholder) and ask them why they wanted the project. Often they’ll tell you some story about a particular group of people that they want to support, or some new context that’s coming along that the software needs to work in. All you need to do to get your first scenario in that situation is ask, “Can you give me an example?”

When the project or capability is about non-functionals such as security or performance, though, this can be a bit trickier. =

I can remember when we were talking to the Guardian editors about performance on the R2 project. “When (other national newspaper) went live with their new front page,” one editor explained, “their site went down for 3 days under the weight of people coming to look at the page. We don’t want that to happen.”

Or, as another organization said, “We went live, and it crashed. It took three months to get the site up and running again. The code was so awful we couldn’t fix it.”

These kind of negative stories are often drivers, particularly when there are non-functionals involved. You can always handle the requirements through monitoring instead of testing, but the conversation can’t follow the usual, “Can you give me an example?” pattern, because all the examples are things that people don’t want.

Instead, keep that negativity, and ask questions like, “What performance would we need to have to avoid that happening to us? Do we have a good security strategy for avoiding the hacking attempt that ended up with (major corporation)’s passwords getting stolen? How do we make sure we don’t crash when we go live?” Keep the focus on the negatives, because that’s what we want to avoid.

When you come to write the scenarios down, whether it’s in terms of monitoring or a test, it’s often worth keeping that negative around. You can create positive scenarios to look at the monitoring boundaries, but the negative reminds people why they’re doing this.

Given we’ve gone live with the front page
When Tony Blair resigns on the same day
Then the site shouldn’t go down under the weight of people reading that news.

Remember that if you’re the first people to solve the problem then you’ll need to try something out, but if it’s just an industry standard practice, make sure you’ve got someone on the team who’s implemented it before.

Part of the power of BDD’s scenarios is that they provide examples as to why the behaviour is valuable. You’ll need to convert this to positive behaviour to implement it, but if avoiding the negatives is valuable, include those too, even it’s just text on a wiki or blurb at the top of a feature file… and don’t be afraid to start there. Negative scenarios are hugely powerful, especially since they often have the most interesting stories attached to them.

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3 Responses to Negative Scenarios in BDD

  1. Pingback: Five Blogs – 24 June 2015 | 5blogs

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