rustlings/exercises/options/options2.rs
lionel-rowe 836134202e
feat(options2): better tests for layered_option
The existing test can be solved with the following:

```rs
        while let Some(integer) = optional_integers.pop() {
            assert_eq!(integer.unwrap(), range);
```

Similarly with `expect(...)`, `unwrap_or(0)`, `unwrap_or_default()`, etc. However, none of these solutions use the learning point of stacking `Option<T>`s.

The updated test can _only_ be solved by stacking `Option<T>`s:

```rs
        while let Some(Some(integer)) = optional_integers.pop() {
            assert_eq!(integer, cursor);
```

With the updated test, using `unwrap` or `expect` will panic when it hits the `None` value, and using `unwrap_or` or `unwrap_or_default` will cause the final `assert_eq!(cursor, 0)`  to panic.
2023-04-21 06:05:25 +01:00

40 lines
1,009 B
Rust

// options2.rs
// Execute `rustlings hint options2` or use the `hint` watch subcommand for a hint.
// I AM NOT DONE
#[cfg(test)]
mod tests {
#[test]
fn simple_option() {
let target = "rustlings";
let optional_target = Some(target);
// TODO: Make this an if let statement whose value is "Some" type
word = optional_target {
assert_eq!(word, target);
}
}
#[test]
fn layered_option() {
let range = 10;
let mut optional_integers: Vec<Option<i8>> = vec![None];
for i in 1..(range + 1) {
optional_integers.push(Some(i));
}
let mut cursor = range;
// TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
// You can stack `Option<T>`s into while let and if let
integer = optional_integers.pop() {
assert_eq!(integer, cursor);
cursor -= 1;
}
assert_eq!(cursor, 0);
}
}