Is there a recommended naming convention for files that contain only extension functions / methods?

Question

In Java, it's simple: the file name for the type is the name of the type suffix plus .java .

In Kotlin, you can write files that do not contain classes. Is there any agreement to name them?

And also, what would you call unit test classes for these functions?

Answer 1

StringExt.kt for a file with String extension functions.

CollectionExt.kt for collection extension features.