I'm setting up Compose Preview Screenshot Testing,...

# compose

[Matti MK]

I'm setting up Compose Preview Screenshot Testing, I have a composable with a date that's formatted with java.time.format.DateTimeFormatter, more specifically using Locale.getDefault().

When I generate the reference screenshots on my local machine the locale formats dates in DD.M.YYYY. However, when I run tests on my CI machine it uses the M/DD/YYYY format. This causes the tests to fail, as now the screenshots look different.

What would be a recommended way to go about this? Of course, providing a Locale as an argument to the Composable would be one option, but I'm wondering if there's a more graceful approach.

[Michael Krussel]

Locale.setDefault() in the test before building the UI

[Michael Krussel]

Ideally, it would probably be best to do screen shot tests in different locals to be able to look at how the screen looks with different translations and time formatting.

[Matti MK]

Thanks! I'll give it a go!

[Matti MK]

Write access not allowed during rendering (user.language)
        at com.android.tools.rendering.security.RenderSecurityException.create(RenderSecurityException.java:52)
        at com.android.tools.rendering.security.RenderSecurityManager.checkPermission(RenderSecurityManager.java:694)
        at java.base/java.util.Locale.setDefault(Locale.java:1110)
        at java.base/java.util.Locale.setDefault(Locale.java:1069)

Unfortunately that didn't quite work

[Matti MK]

I guess the way here would be to pass the Locale as an argument to the Composable and define a default value for the parameter (Locale.getDefault())..

[Michael Krussel]

Could use a CompositionLocal instead of a parameter

[Matti MK]

Interesting! I wouldn't have thought of using CompositionLocal, but at the same time I've got very little experience with it so maybe that's why.

I think the date is used in so few places, that the arg with a default parameter seems like an easier approach here.