Require test class for groovy dsl jenkins shared library

I require a test class([login to view URL]) for my jenkins shared library that sends an email when a job finishes. I have the groovy class for this already([login to view URL]), but i am struggling to create tests for it, due to lack of groovy knowledge IMPORTANT: - Tests just need to check if functionality is performing as expected - Please use the shared library folder structure for testing (image attached below) - Please use this testing framework : [login to view URL] - DO NOT BID IF YOU HAVE NO EXPERIENCE IN JENKINS / GROOVY , no time wasters please, will require this to be completed in less than 24 hours! - I will provide a code to help test the library locally - Please use VSCode to test locally