Hi ram,
Any Upgrade or Patch should be tested against your business critical functions. Generally, reading the patch notes + doing a test through your important users use cases is always a good idea.
For major releases, choose most of the functionality in the platform but in order to do that, you can engage the process owners and have some automated tests that you can run as well. For patch level upgrades (as per your ask here) you can test the major functionality and run the automated tests. For security patch upgrades, do automate testing and some really high level checks.
The upgrades and patches do introduce risk but given that there are monthly upgrades, we'd need a team of full time testers so just try to match the testing effort to the degree of change.
Mark my answer correct & Helpful, if Applicable.
Thanks,
Sandeep
