Combinatorial explosion of states is a nightmare, IME it means that the abstraction behind is not the right one. You really don't want to have a function that

Combinatorial explosion of states is a nightmare, IME it means that the abstraction behind is not the right one. You really don't want to have a function that branches a lot inside. It's very difficult to test. When you think of adding a flag, run in your head 2^n, this will give you the least number of tests needed. Do you really want to write all of them?