Most important to test for 9.0.5:
- share grouping fix for received shares: Group shares with same source and target by rullzer · Pull Request #25113 · owncloud/core · GitHub
And for 9.1.1:
- test any sharing scenario, but especially if you had memory issues (aka shared storage recursion hell): File Sharing stack overflow, memory issue, crash, CSRF issue on 9.1.0 · Issue #25557 · owncloud/core · GitHub