Hello Kirill,
this is my late response to https://lab.nexedi.com/nexedi/wendelin/-/merge_requests/160#note_223155 :).
There is some duplication between test_bigfile_filezodb_discard_data and test_zbigarray_resize_discards_data, but I prefered overlaps to test coverage gaps.
I'm waiting for ZODB4-wc2, ZODB5 and ZODB6 (not started yet) tests (I added for_testrunner_1 branch, similar to what we have in the SlapOS and ERP5 repositories).
Best, Levin