The phrase "training ground" refers to a place or area where practice and learning take place, usually to develop skills or prepare for a specific activity or task. Full definition
It's also a good training ground for where the real action happens, online against real opponents. (thatvideogameblog.com)
Counseling supervision not only serves to meet state licensure requirements, but also provides fertile training ground in a mentorship setting. (onlinecounselingprograms.com)
He thinks of his former career as a sort of training ground that prepared him for his new venture as an agent. (realtormag.realtor.org)