I ran the PCT against the git-plugin using JDK11, and AbstractGitSCMSourceRetrieveHeadsTest failed during the initial run. After consulting with Adrien Lecharpentier I removed dependency versions for powermock-module-junit4, powermock-api-mockito2, and then mockito-core and reran the PCT specifying just the AbstractGitSCMSourceRetrieveHeadsTest. This resulted in an IllegalAccessError based on usage of com.thoughtworks.xstream.converters.DurationConverter.
Mark Waite if you have some time to check this is actual or not, that would be great. If you cannot, then that is absolutely fine, please then tell us so that we dedicate some time to analyze and fix this.
I'm reasonably confident this is actual. The mocking libraries tend to be problematic. I'm quite weak in use of mocks and mocking libraries and don't have time to investigate this currently. If there is someone with experience using mocking libraries, they will find and resolve the problem sooner than I will.
Mocking libraries have been removed from git plugin 3.10.0. Minimum Java requirement has been increased from Java 7 to Java 8. Minimum Jenkins version has increased from 1.642 to 2.121.1. PCT now passes.