"Atomic" tests only test 1 specific "feature".
One could start clicking around in the user interface of a specific application, where one option (checkbox, item in listbox etc) would arguably equal one "feature" (thereby limiting the testing possibilities to the features supported by this application)
Another way would be creating documents by hand or using a low-level ODF library.
One should always be able to link the test to (a part of) a numbered item/paragraph of the ODF specification(s)
- read: load a test file
- write: write a file (manually or by using API) and compare it to the test file
- roundtrip: load test file and save it to another file, compare the files
ODF versions and overlap
Note that, due to considerable overlap/compatibility between the various ODF versions, test files often can be used for testing multiple ODF versions.