As owner of the file, create a situation where:
The user testUser can read the file (by knowing its path).
The user testUser can see only that one file content and nothing else:No names of files and directories, no access to anything else; even if the user knew more than the one filepath.
Nobody else (except root and you) can access any of your other directories or files in any way.
Use your user_8e1134-test user for testing, and finally grant the appropriate permissions to testUser.
I have tried chown which gives operation not permitted, can't use sudo , and tried another command satcl i believe , that also did not work.