Repro for https://youtrack.jetbrains.com/issue/KT-44890: gradle recompiles test sources when a resource changes (but not the 'main' code).
This can be triggered by running test_build.sh which gives the following output:
Doing build with unchanged resources (output in build1.txt)
Skipping task ':compileKotlin' as it is up-to-date.
Skipping task ':processResources' as it is up-to-date.
Skipping task ':compileTestKotlin' as it is up-to-date.
Skipping task ':test' as it is up-to-date.
4 actionable tasks: 4 up-to-date
Rebuilding after modifying one resource file (output in build2.txt)
Skipping task ':compileKotlin' as it is up-to-date.
Task ':processResources' is not up-to-date because:
Task ':compileTestKotlin' is not up-to-date because:
Task ':test' is not up-to-date because:
4 actionable tasks: 3 executed, 1 up-to-date
I would expect only :processResources and :test to run after a resource change, not :compileTestKotlin. (Note that :compileKotlin is still considered up-to-date regardless of the resource change).