TL;DR
In this post I will explain one quick, but very important, test idea. Inverse feature.
In order to avoid complex mathematical description and proof, let’s use simple plain explanation. Inverse feature does exactly the opposite from the original feature. And operates on output data of the original feature. Ad in the end, we should get back original data.
Here are few examples.
Every browser has zoom feature. Let's zoom in for 10% of this blog post, and again, zoom out on same blog post for 10%. You should view blog post in starting resolution. Or you have feature that exports list of users. The best way to test this feature is using import feature of users. Export users, delete them, do the import, you should get original list of users.
Inverse feature is very important quick test idea, because you can test original feature very quickly. Also, users will be very satisfied with your product if features of that product come in pairs.
This quick test idea is fallible because you can have four possible combinations:
both features work, both features fail, original feature fails, inverse feature fails.
It is important to be aware that using only this quick test method is not enough.
Which method would you use to help you in case when both features fail?
