Test them in the sense of thinking it through by working through the cases, it's more to help internalize the idea. And writing things down is forcing my mind

Test them in the sense of thinking it through by working through the cases, it's more to help internalize the idea. And writing things down is forcing my mind to serialize and deserialize ideas, and I think that helps the process. (I'm not actually doing this often for Java generics, but I've been working on some other type theory stuff and I found it helped me get beyond "I understand this" to "I now feel relatively fluent expressing these ideas.")