To reproduce, run the kotlinCheck task. Right after bson-kotlinx:test task complete, observe that the following test result files have been created:
% ls ./bson-kotlinx/build/test-results/*/TEST-*.xml ./bson-kotlinx/build/test-results/test/TEST-org.bson.codecs.kotlinx.KotlinSerializerCodecProviderTest.xml ./bson-kotlinx/build/test-results/test/TEST-org.bson.codecs.kotlinx.KotlinSerializerCodecTest.xml
Now wait for kotlinCheck to complete. The files are gone. All the other tests result files remain, though, e.g.
% ls ./bson-kotlin/build/test-results/*/TEST-*.xml ./bson-kotlin/build/test-results/test/TEST-org.bson.codecs.kotlin.DataClassCodecProviderTest.xml ./bson-kotlin/build/test-results/test/TEST-org.bson.codecs.kotlin.DataClassCodecTest.xml
The files seem to be deleted right before kotlinCheck completes.
This is a problem when running the task in Evergreen. If we run kotlinCheck with --continue (as we should) then even if the bson-kotlinx tests fail they won't show up as failures in the Tests view.