Protect against forgetting to call a test case evaluation function

test_guard.rs

fn make_test_evaluator() -> Box<Fn(YourTestCaseTypeHere)> {
    use std::cell::RefCell;

    struct EvalGuard(bool);

    impl Drop for EvalGuard {
        fn drop(&mut self) {
            if !self.0 {
                panic!("Did not actually evaluate test cases");
            }
        }
    }

    let eval_guard = RefCell::new(EvalGuard(false));

    Box::new(move |test_case: YourTestCaseTypeHere| {
        assert!(test_case.does_stuff_correctly(), "doesn't do stuff correctly");

        eval_guard.borrow_mut().0 = true;
    })
}