I'm running into situations where tests pass fine when run individually or serially, but some of them will fail when run in the standard concurrency from the plugin parent. Output from such a failed test looks like https://gist.github.com/abayer/7eb7bb645efa181ecd869b04017fea74 - note that the compilation error there is actually the desired result, but when I use story.j.assertLogContains("MultipleCompilationErrorsException: startup failed"), the test fails, and the test failure output doesn't have anything after First time build. Skipping changelog.. The tests are fairly simple - along the lines of:

        // Stuff constructing sampleRepo
        WorkflowJob p = story.j.jenkins.createProject(WorkflowJob.class, "p");
        p.setDefinition(new CpsScmFlowDefinition(new GitStep(sampleRepo.toString()).createSCM(), "Jenkinsfile"));
        WorkflowRun b = p.scheduleBuild2(0).waitForStart();
        story.j.assertBuildStatus(Result.FAILURE, story.j.waitForCompletion(b));
        story.j.assertLogContains("MultipleCompilationErrorsException: startup failed:", b);