[OffsetDateTime.format] Different result between robolectric and emulator

[likai79511]

Description

When i execute OffsetDateTime.format, different results will occur between Robolectric and Device/Emulator.

Steps to Reproduce

@Test
fun test() {
    Locale.setDefault(Locale("en", "AU"))

    val time = OffsetDateTime.parse("2023-01-01T10:00:00Z")
    val formatter = DateTimeFormatter.ofPattern("d MMM yyyy")

    println("FINGERPRINT: ${Build.FINGERPRINT}\nresult:${time.format(formatter)}")
}

Robolectric	device/emulator

Robolectric : 1 Jan. 2023 (with a ".")
Device/Emulator: 1 Jan 2023

Robolectric & Android Version

org.robolectric:robolectric:4.9.2
junit:junit:4.13.2

Link to a public git repo demonstrating the problem:

[hoisie]

Unfortunately OffsetDateTime is a Java core class, so any differences are due to the implementation differences between the JDK and Libcore (Android's implementation of the Java core classes).

This is the Android version:
https://cs.android.com/android/platform/superproject/+/master:libcore/ojluni/src/main/java/java/time/OffsetDateTime.java;l=122?q=OffsetDateTime&sq=

[okamayana-tinyspeck]

Unfortunately OffsetDateTime is a Java core class, so any differences are due to the implementation differences between the JDK and Libcore (Android's implementation of the Java core classes).

This is the Android version: https://cs.android.com/android/platform/superproject/+/master:libcore/ojluni/src/main/java/java/time/OffsetDateTime.java;l=122?q=OffsetDateTime&sq=

Is this also the case for DateTimeFormatter? Also, are there any workarounds?

[MGaetan89]

It's the same for DateTimeFormatter, yes.
We have documented it here, for the timezone difference: https://robolectric.org/best-practices/#android-libcore-and-openjdk-have-different-implementations

For your issue regarding month name, we can add a dedicated section, if there is a known alternative/workaround.

[MGaetan89]

We've added a section on Robolectric's website for this case: https://robolectric.org/best-practices/#month-names
As @hoisie pointed out, these classes are part of the Java API, and Robolectric cannot alter their behavior.
You can run your tests on an Android device to get the correct result.