Rust in writing test cases

Somewhat similar

#[derive(Debug)]
pub struct Rectangle {
    length: u32,
    width: u32,
}

impl Rectangle {
    pub fn can_hold(&self, other: &Rectangle) -> bool {
    self.length > other.length && self.width > other.width
    }
}

pub fn add_two(a: i32) -> i32 {
    a + 2
}

pub fn greeting(name: &str) -> String {
    format!("Hello {}!", name)
}

pub struct Guess {
    value: i32,
}

impl Guess {
    pub fn new(value: i32) -> Guess {
    if value < 1 {
        panic!("Guess value must be great than or equal 1, got {}.", value);
    } else if value > 100 {
        panic!("Guess value must less than or equal to 100, got {}.", value);
    }

    Guess {
        value
    }
    }
}


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

    #[test]
    fn larger_can_hold_smaller() {
    let larger = Rectangle { length: 8, width: 7 };
    let smaller = Rectangle { length: 5, width: 1 };
    assert!(larger.can_hold(&smaller));
    }

    #[test]
    fn smaller_cannot_hold_larger() {
    let larger = Rectangle { length: 8, width: 7 };
        let smaller = Rectangle { length: 5, width: 1 };
        assert!(!smaller.can_hold(&larger));
    }
    
    #[test]
    fn it_add_two() {
    assert_eq!(4, add_two(2));
    }

    #[test]
    fn greeting_contains_name() {
    let result = greeting("Carol");
     assert!(result.contains("Carol"));
    }

    #[test]
    #[should_panic(expected = "Guess value must be less than or equal to 100")]
    fn greater_than_100() {
    Guess::new(200);
    }

    /*
    #[test]
    fn it_works() -> Result<(), String> {
    if 2 + 2 == 4 {
        Ok(())
    } else {
        Err(String::from("two plus two does not equal four"))
       }
    }
    */
}