I want Jenkins to automatically find and run the test suite for every branch that is part of an open pull request. Is this possible with some Jenkins plugin I have not found?
One method that should work is you could rename the branch when it is "prepared for integration" and ready to be tested.
A naming convention like prep/my_feature.
Then in the Jenkins git plugin you can configure the branch names that you want it to look at for building. You can have it match 'prep/*'.
We used to do this for all our feature branches using a prefix of 'dev/' to mark the feature branches that should have the autobuild run for them. Seems to work pretty well.