Functional or non-functional issue: a button kept pressed causes troubles

Question

I found that an interesting example and I struggle with classification (which is quite important for our metrics): There is an issue with a hardware button, when it is kept pressed, it toggles the ON/OFF conditions (as if holding a power button caused continual turning on/turning off of a device). The action should happen only once, of course. I struggle whether this is a functional or a non functional issue.

The spec says: when the button is pressed and X is not shown, show it. When it is pressed and X is shown, hide it.

It does work like that but in addition, continuous holding of the button causes X to show & hide repeatedly.

I am thinking about non-functional requirement but cannot think of any that would fit.

Answer 1

Have you considered that it's not an issue in the design or implementation, but a defect in the requirements? The spec that you quoted doesn't mention what to do in this particular case. I would call this a defect in the requirements and say that the requirement was incomplete or unclear.

When classifying this requirement, I would try to avoid classifying it as functional or non-functional, since the defect is in your requirements specification, not a product that has functional and non-functional characteristics. If that's not possible, if you have or can create a "documentation" type under non-functional defects, then that would be suitable and could be used to capture other requirements, design document, test plan/procedure document, user manual, and so on defects as well. Alternatively, "usability" would be my next choice.