Challenge 2: Testing a Divide-by-Zero Panic — Possible Solution
====================================================================

pub fn divide(a: f64, b: f64) -> f64 {
    if b == 0.0 {
        panic!("cannot divide by zero");
    }
    a / b
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    #[should_panic]
    fn dividing_by_zero_panics() {
        divide(10.0, 0.0);
    }
}

WHY THIS WORKS AS AN ANSWER
------------------------------
divide explicitly calls panic!("cannot divide by zero") when b is
0.0 — reusing Course 1 Chapter 7's panic! for a genuinely unrecoverable
situation (per that chapter's own guidance: panic! for "this should
never happen," which a caller passing 0.0 as a divisor to a raw divide
function reasonably counts as, absent Result-based error handling).

The test function itself calls divide(10.0, 0.0) with NO assertion
macro at all — it doesn't need one. Because it's marked #[should_panic],
this chapter's own rule applies: the test PASSES specifically because
the call panics, and would FAIL if divide somehow returned normally
instead (which would indicate the zero-check was broken or removed).
This inverts the usual pass/fail logic on purpose — exactly the tool
this chapter introduced specifically for testing that error conditions
are correctly detected and rejected, rather than testing a successful,
non-panicking code path.