Test sample-extension-plugin in job scheduler


I have installed the sample-extension-plugin of the job scheduler to my local elasticsearch instance, according to the link (job-scheduler/sample-extension-plugin at main · opendistro-for-elasticsearch/job-scheduler · GitHub). However, I have no idea how to test this sample plugin. There is no proper guide/documentation and example on this. Please help guide me on this.

If I want to develop my own extension plugin of the job scheduler, is there somewhere I could find the documentation of the development guide?

I am quite struggling to make it working and do further development without finding any example/reference.

Thank you,