[keycloak-user] Best setup to extend Keycloak

Hello, What is the best setup to develop custom SPI for Keycloak. I just skimmed the example codes in github and wondered on how to test my codes. Not TDD way of testing but a simple, hey, will this run properly? Anyway, the reason I need to extend this is to create an authentication flow that will use your internal SMS api for subscriber verification. Regards,Francis