When accessed through a JobDSL script, the xUnit plugin will cause the job generation to effectively fail if the JUnit plugin is installed but disabled. ("effectively fail" means that the job resulting from the generated XML does not include all elements specified in the DSL, while the spawn job exits as SUCCESS without any error output.)

I investigated this effect with Daniel from the JobDSL team (https://groups.google.com/forum/#!topic/job-dsl-plugin/n1GgzesLebA) and it seems clear it's not a JobDSL issue in the first instance.

Apparently, xUnit needs JUnit to be active, but it checks only on the installation status of JUnit, not on whether it is activated. Activating JUnit solves the above problem, but it would be better if xUnit checked back on the activation status of JUnit and threw a corresponding error.