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11.4.1. 验证错误处理的情况
测试函数出了验证代码的返回值是否正确#xff0c;还需要验证代码是否如预期的去处理了发生错误的情况。比…喜欢的话别忘了点赞、收藏加关注哦对接下来的教程有兴趣的可以关注专栏。谢谢喵(ω)
11.4.1. 验证错误处理的情况
测试函数出了验证代码的返回值是否正确还需要验证代码是否如预期的去处理了发生错误的情况。比如说可以编写一个测试来验证代码是否在特定情况下发生了panic!。
这种测试需要为函数额外增加should_panic属性。使用它标记的函数如果在函数内发生了恐慌则代表通过测试反之就失败。
看个例子
pub struct Guess {value: i32,
}impl Guess {pub fn new(value: i32) - Guess {if value 1 || value 100 {panic!(Guess value must be between 1 and 100, got {value}.);}Guess { value }}
}#[cfg(test)]
mod tests {use super::*;#[test]#[should_panic]fn greater_than_100() {Guess::new(200);}
}结构体Guess有一个存储u32类型数据的字段value它有一个关联函数new用于创建一个Guess实例但前提是传进new的参数大于1小于100否则就要恐慌。greater_than_100这个测试函数测试给new函数传入大于100的值这时候应该发生恐慌所以为这个测试函数添加了一个should_panic的attribute(属性)也就是写#[should_panic]。
测试结果
$ cargo testCompiling guessing_game v0.1.0 (file:///projects/guessing_game)Finished test profile [unoptimized debuginfo] target(s) in 0.58sRunning unittests src/lib.rs (target/debug/deps/guessing_game-57d70c3acb738f4d)running 1 test
test tests::greater_than_100 - should panic ... oktest result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00sDoc-tests guessing_gamerunning 0 teststest result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s下面来人为引入bug把new函数里的value 100的判断去掉
pub struct Guess {value: i32,
}impl Guess {pub fn new(value: i32) - Guess {if value 1 || value 100 {panic!(Guess value must be between 1 and 100, got {value}.);}Guess { value }}
}#[cfg(test)]
mod tests {use super::*;#[test]#[should_panic]fn greater_than_100() {Guess::new(200);}
}这时候测试函数中的Guess::new(200);就不会恐慌但是因为它添加了should_panic这个attribute所以本应该恐慌的函数没有恐慌就会导致测试失败
$ cargo testCompiling guessing_game v0.1.0 (file:///projects/guessing_game)Finished test profile [unoptimized debuginfo] target(s) in 0.62sRunning unittests src/lib.rs (target/debug/deps/guessing_game-57d70c3acb738f4d)running 1 test
test tests::greater_than_100 - should panic ... FAILEDfailures:---- tests::greater_than_100 stdout ----
note: test did not panic as expectedfailures:tests::greater_than_100test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00serror: test failed, to rerun pass --lib11.4.2. 让should_panic更精确
有的时候使用should_panic进行的测试会有点含糊不清因为它仅仅能够说明被检查的代码是否发生了恐慌即使这个恐慌和程序员预期的恐慌不一样。
为了使测试更精确可以为should_panic添加一个可选的expected参数。这样程序就会检查失败消息中是否包含所指定的文字。
看个例子
pub struct Guess {value: i32,
}impl Guess {pub fn new(value: i32) - Guess {if value 1 {panic!(Guess value must be greater than or equal to 1, got {value}.);} else if value 100 {panic!(Guess value must be less than or equal to 100, got {value}.);}Guess { value }}
}#[cfg(test)]
mod tests {use super::*;#[test]#[should_panic(expected less than or equal to 100)]fn greater_than_100() {Guess::new(200);}
}在刚才的结构体上稍微进行了修改把new函数里value 1和value 100的情况分开写了两个不同的恐慌信息。给should_panic属性添加了expected参数后面跟的就是期待的报错信息。只有测试函数恐慌并且恐慌信息包括期待的报错信息才算测试成功否则就算失败。
这个程序肯定能成功。
一样的套路我们来手动引入错误比如我们把new函数里小于1和大于100的恐慌信息交换一下
pub struct Guess {value: i32,
}impl Guess {pub fn new(value: i32) - Guess {if value 1 {panic!(Guess value must be less than or equal to 100, got {value}.);} else if value 100 {panic!(Guess value must be greater than or equal to 1, got {value}.);}Guess { value }}
}#[cfg(test)]
mod tests {use super::*;#[test]#[should_panic(expected less than or equal to 100)]fn greater_than_100() {Guess::new(200);}
}测试结果
$ cargo testCompiling guessing_game v0.1.0 (file:///projects/guessing_game)Finished test profile [unoptimized debuginfo] target(s) in 0.66sRunning unittests src/lib.rs (target/debug/deps/guessing_game-57d70c3acb738f4d)running 1 test
test tests::greater_than_100 - should panic ... FAILEDfailures:---- tests::greater_than_100 stdout ----
thread tests::greater_than_100 panicked at src/lib.rs:12:13:
Guess value must be greater than or equal to 1, got 200.
note: run with RUST_BACKTRACE1 environment variable to display a backtrace
note: panic did not contain expected stringpanic message: Guess value must be greater than or equal to 1, got 200.,expected substring: less than or equal to 100failures:tests::greater_than_100test result: FAILED. 0 passed; 1 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00serror: test failed, to rerun pass --lib失败消息表明此测试确实发生了恐慌但是恐慌消息不包含less than or equal to 100预期字符串。在这种情况下我们确实收到的恐慌信息是 Guess value must be greater than or equal to 1, got 200.。根据这个就可以纠错。
