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测试4：exercises/tests/tests4.rs
题目
rust
// tests4.rs
//
// Make sure that we're testing for the correct conditions!
//
// Execute `rustlings hint tests4` or use the `hint` watch subcommand for a
// hint.
// I AM NOT DONE
struct Rectangle {
width: i32,
height: i32
}
impl Rectangle {
// Only change the test functions themselves
pub fn new(width: i32, height: i32) -> Self {
if width <= 0 || height <= 0 {
panic!("Rectangle width and height cannot be negative!")
}
Rectangle {width, height}
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn correct_width_and_height() {
// This test should check if the rectangle is the size that we pass into its constructor
let rect = Rectangle::new(10, 20);
assert_eq!(???, 10); // check width
assert_eq!(???, 20); // check height
}
#[test]
fn negative_width() {
// This test should check if program panics when we try to create rectangle with negative width
let _rect = Rectangle::new(-10, 10);
}
#[test]
fn negative_height() {
// This test should check if program panics when we try to create rectangle with negative height
let _rect = Rectangle::new(10, -10);
}
}请确保我们的测试条件正确。
题目解析
题目中定义了长方形结构体Rectangle，并定义了new方法，要求width和height必须是正数，否则会直接panic。
我们先来看第一个单元测试，用于测试长方形的宽度和高度是否正确：
rust
#[test]
fn correct_width_and_height() {
// This test should check if the rectangle is the size that we pass into its constructor
let rect = Rectangle::new(10, 20);
assert_eq!(???, 10); // check width
assert_eq!(rect.width, 10); // check width
assert_eq!(???, 20); // check height
assert_eq!(rect.height, 20); // check height
}接着看第二个单元测试，由于宽度是复数，这里应该会panic，为了能够让测试通过，我们可以使用#[should_panic]
rust
#[test]
#[should_panic]
fn negative_width() {
// This test should check if program panics when we try to create rectangle with negative width
let _rect = Rectangle::new(-10, 10);
}同理，第三个单元测试高度是复数，也会panic,我们也需要添加#[should_panic]
rust
#[test]
#[should_panic]
fn negative_height() {
// This test should check if program panics when we try to create rectangle with negative height
let _rect = Rectangle::new(10, -10);
}