unit-testing - 消息带有撇号时，should_panic预期无法正常工作

Question

我的代码失败，并显示以下消息"Didn't get a filename"但是我的should_panic没有检测到/匹配这个

#[test]
#[should_panic(expected="Didn't get a filename")]

产生结果

note: panic did not contain expected string
      panic message: `"called `Result::unwrap()` on an `Err` value: \"Didn\\\'t get a filename\""`,
 expected substring: `"Didn\'t get a filename"`

显然，解决方法是避免变音符号，但是我无法弄清楚如何转义匹配字符串。

Answer 1

Result::unwrap()要求错误类型实现Debug。因此，当创建紧急消息时，它将使用调试打印。对于字符串，该字符串将包含引号并转义某些字符:

fn main() {
    let error = "Didn't get a filename";
    println!("normal: {}", error);
    println!("debug : {:?}", error);
}

normal: Didn't get a filename
debug : "Didn\'t get a filename"

似乎通常遵循 char::escape_default 的规则。
因此，在紧急消息中打印的实际字符串包括一个附加的 \:

#[test]
#[should_panic(expected = "Didn\\'t get a filename")]
fn panics() {
    let result: Result<(), &str> = Err("Didn't get a filename");
    result.unwrap();
}