I failed these tests initially, but when I looked at them, I realized that a reasonable interpretation of the instructions would produce different results.

Specifically, the tests test_bad_age, test_missing_age, and test_missing_name are not testing the behavior that I inferred from the instructions. I understood the instruction (4) to be "If the name is empty, return [a Person with the default name]" and (6) to be "If parsing the age fails, return [a Person with the default age]".

The reason my brain immediately jumped to this incorrect conclusion is that the context makes it clear that, in such a case, it's possilbe the rest of the information is valid--so why throw away valid information?

I don't think the tests or instructions are wrong, only that they could be clearer (or better).

For reference, here is what my initial implementation looked like:

impl From<&str> for Person {
    fn from(s: &str) -> Self {
        let strs: Vec::<&str> = s.split(',').collect();
        match strs[..] {
            [in_name, in_age] => Person {
                name: match in_name {s if s.is_empty() => Person::default().name, s => s.to_string() },
                age: in_age.parse::<u8>().unwrap_or(Person::default().age)
            },
            _ => Person::default()
        }
    }
}