Generally this type of testing is ok as long as it’s not detrimental to service in terms of negatively affecting others on the platform / your hypervisor. Our Security team at that point will take action on that Droplet or if the pattern repeats the account.
This would include reasons like, but is not limited to: large bandwidth usage, CPU resource usage, etc. originating from or sending to a Droplet.
Our Security Operations team would always try to be transparent with communication if the above scenarios ever did occur. You would get a ticket asking for more details on what you were doing + to stop the negative effects. If you could spread the penetration tests across several Droplets in various regions, that may help to reduce the load for one hypervisor in particular.
You can read our Terms of Service here to ensure no other issues from your use-case will alert our Security Operations team: https://www.digitalocean.com/legal/terms-of-service-agreement/
If you have any other questions or need clarification on anything, just write back in and let us know! :)