Option to ignore part of snapshot when comparing

[legoesbenr]

We here at LEGO are happy users of the swift-snapshot.testing framework.
Thank you for supporting this.

Is it possible ignore areas or parts of a snapshot in the case that we expect there to be differences.

Use case:
We use snapshotting as image to monitor UI changes. In a view we have counters that count down, which means that the text in the view is changing. Locally this is not a problem because the test runs within the same second but in XCodeCloud sometimes the test takes longer and therefore the text has changes, which causes the tes to fail - obviously.

Is it possible to ignore either a defined area of the image or a certain view i.e. by name?

Are there other ways to handle this case - I assume the same will be a problem with i.e. a clock?

[fespinoza]

just as a suggestion, you can try to see if you can pass the time value from outside the view as a parameter, then you have a static time for snapshotting purposes.

[legoesbenr]

Thanks for the idea. That would need me to design my architecture unnecessarily complex just to accommodate to test this scenario, which is a pretty bad pattern.

Im using the TimeLineView which is a SWIFTUI built in feature that renders a countdown - or up, from a timestamp. So I just cant pass a static timestamp.

TimelineView(.everyMinute) { context in
Text(estimatedCoolingCompletion, style: .relative)
.monospacedDigit()
}

[mbrandonw]

Are there other ways to handle this case - I assume the same will be a problem with i.e. a clock?

Yeah, we personally would recommend controlling your dependency on time via either a clock, combine scheduler, and some other means. That would even allow you to snapshot your view deterministically at a specific time, which could be handy if there are things in the UI that change with respect to the timer.

[legoesbenr]

Please see my response above. I am controlle the timestamp offset, but using the built-in TimeLineView, in which I cant control/freeze it.

Implementing a countdown and then adding a freeze feature for the sole purpose of the test is not a good approach.

I agree with you that I could over engineer this and implement my own countdown separately from the view and then it would be possible.

Thanks for you feedback. I'm still hanging on the the hope that someone has an idea for shaping the test and not the the actual feature for this scenario.

[mbrandonw]

That is just the cost of using TimelineView. It's great for what it does, but it also wasn't built with testability in mind.

And just as you feel that abandoning TimelineView may be "over-engineering", we also feel that supporting the notion of "ignored regions" is not the right choice for this library. Screenshot tests are already precarious enough with minute pixel differences that we don't want to further add complications for ignored regions of pixels that can shift from test-to-test.

[legoesbenr]

I get your point. I will se if I can work around it.
Thanks.