I need unit tests for this rust function:

```
fn fizzbuzz(n: usize) -> String {
    match (n % 3, n % 5) {
        (0, 0) => "fizzbuzz".to_string(),
        (0, _) => "fizz".to_string(),
        (_, 0) => "buzz".to_string(),
        _ => n.to_string(),
    }
}
```
Here is a Rust function with some test cases using the Test library:


