There aren't any standards and guidelines regarding the testing of shared pipeline libraries.
The expected folder structure (https://issues.jenkins-ci.org/browse/JENKINS-33925) doesn't play well with Maven or Gradle and it isn't clear whether committing and pushing anything else but the expected folder tree would break the implementation.

I couldn't find any examples apart from https://github.com/jenkinsci/workflow-cps-global-lib-plugin/blob/master/src/test/java/org/jenkinsci/plugins/workflow/cps/global/WorkflowLibRepositoryTest.java

Tried to integrate a similar approach into an example standard shared library but it's of limited use, see https://github.com/zhelyan/jenkins-pipeline-test-harness

Any hints?