I have read this post and this ros article but the answers there still didn't shed light. I can see rosunit.unitrun uses the unittest framework while rosunit.rosrun uses the rostest framework. However, it seems that both can run unittest test cases and suites. ChatGPT (which should not be regarded as a source of truth) indicates that rosunit.rosrun("my_package", "my_node") is valid, but I'm not sure if that's the case.