Both the fib and prime factor examples are shit. The tests are individual cases which is treating the input as a Cartesian product (a point on a line since thes

Both the fib and prime factor examples are shit. The tests are individual cases which is treating the input as a Cartesian product (a point on a line since these are single-variable functions). What you want are sets. The inputs for both are all natural numbers. However, this doesn't tell you much, there's still a lot of state to work with. So what you want are end conditions, but again that doesn't tell you much. Tests are no substitute for reasoning and TDD is just another fad.