Hi, i'm trying to write tests for a composable function that does calculations on a lazy list when i...

# compose

[Fabio Berta]

Hi, i'm trying to write tests for a composable function that does calculations on a lazy list when it's scrolled. I'm using

listNode.performTouchInput {
  swipeUp(endY = height - 3.dp.toPx())
}

to simulate a scroll. Now this works fine if I'm using higher values than 3dp but since I want to test a specific edge case, I'd like to use low values. However, by capturing before and after screenshots, I noticed that when using low values like 3.dp , it doesn't scroll at all. Is there a minimum threshold or something?

[Kirill Grouchnikov]

This is probably under the system-level touch slop

[Kirill Grouchnikov]

Print the value of ViewConfiguration.get(context).scaledTouchSlop to verify that threshold

[Fabio Berta]

that prints 22

[Fabio Berta]

ok so I would need to swipe by at least 22px

[Fabio Berta]

thx

[Kirill Grouchnikov]

Probably not pixels, you would want to stay in the dp land

[Kirill Grouchnikov]

Or maybe pixels if that’s what swipeUp operates in

[Kirill Grouchnikov]

One last thing - don’t hardcode 22 into your test. Use scaledTouchSlop so that it works across different devices

[Fabio Berta]

yeah, i'm looking into how to incorporate this best. I don't think I can test my edge cases given this limitation.

[Kirill Grouchnikov]

Touch slop will be there for the “real” user interaction on device. Not sure what is the edge case you’re trying to test, but it might be that you’re trying to test something that can not happen in the app / on device.

[Fabio Berta]

yeah, thinking about, my test was not setup right. What I wanted is to test is that something changed at the right moment when scrolling. So I scrolled very close to the breaking point, asserted everything is how it should be, then scrolled just passed it (hence the small value) and asserted the change. But it's clear to me now that this is not how the user would interact. I need to restructure the test to do a bigger swipe just over the breaking point and assert then.

[Fabio Berta]

Thanks for your input, very helpful!