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有可能改变整个恐慌信息吗?

rust unit-testing

Boiethios · 技术社区 · 9 年前

Assert.That(someInt, Is.EqualTo(42));
Assert.That(someList, Has.Member(someMember));

我喜欢这种代码,因为它看起来像英语,很容易阅读。

我在玩Rust,看看能否创建一个能给人同样感觉的库:

use std::fmt::Debug;

struct Is;

enum Verb<T> {
    EqualTo(T),
}

impl Is {
    fn equal_to<T>(&self, obj: T) -> Verb<T> {
        Verb::EqualTo(obj)
    }
}

#[allow(non_upper_case_globals)]
const is: Is = Is{};

fn assert_that<T: Eq + Debug>(obj: T, verb: Verb<T>) {
    match verb {
        Verb::EqualTo(rhs)    => assert_eq!(obj, rhs),
    }
}

fn main() {
    assert_that(42, is.equal_to(42));
    assert_that(42, is.equal_to(0));
}

这很好,但有一点:当代码在 assert_that(42, is.equal_to(0)) ,恐慌给出的线是 assert_eq!(obj, rhs) (

2 回复 | 直到 8 年前

Shepmaster Tim Diekmann 9 年前

panic! 打印。

有 a proto-RFC

How to write a panic! like macro in Rust? 惊恐 宏,但它选择分解整个过程,而不仅仅是当前线程。

panic::set_hook

use std::cell::Cell;

thread_local! {
    static ASSERT_LOCATION: Cell<Option<(&'static str, u32)>> = Cell::new(None)
}

fn report_my_error(info: &std::panic::PanicInfo) {
    match info.location() {
        Some(location) => {
            let file = location.file();
            let line = location.line();
            println!("The panic actually happened at: {}, {}", file, line);
        }
        None => println!("I don't know where the panic actually happened"),
    }

    ASSERT_LOCATION.with(|location| if let Some((file, line)) = location.get() {
        println!(
            "But I'm going to tell you it happened at {}, {}",
            file,
            line
        );
    });

    if let Some(msg) = info.payload().downcast_ref::<&str>() {
        println!("The error message was: {}", msg);
    }
}

#[test]
fn alpha() {
    std::panic::set_hook(Box::new(report_my_error));

    ASSERT_LOCATION.with(|location| {
        location.set(Some((file!(), line!())));
    });

    panic!("This was only a test")
}

您需要确保在每次测试中设置了紧急处理程序,然后设置位置信息。您可能还需要更新紧急处理程序,将位置信息设置回 None 以避免线程之间的位置信息泄漏。

您可能希望编写自己的宏,用户可以在测试中使用该宏隐式设置行号。类似于此的语法可以为该设置代码提供生存空间:

assert_that!(42, is.equal_to(0));

assert_that(file!(), line!(), 42, is.equal_to(0));

我可能会把恐慌处理程序放在 assert_that

Shepmaster Tim Diekmann 9 年前

您可能有兴趣使用 spectral ,一个库,提供流畅的锈病测试断言。如果你看看他们 implementation line!() 和 file!() assert_that! 库中定义的宏。

用法如下:

#[test]
fn example() {
    assert_that!(2).is_equal_to(4);
}

failures:

---- utils::tests::example stdout ----
        thread 'utils::tests::example' panicked at '
        expected: <4>
        but was: <2>

        at location: src/utils.rs:344
', /home/example/.cargo/registry/src/github.com-1ecc6299db9ec823/spectral-0.6.0/src/lib.rs:343
note: Run with `RUST_BACKTRACE=1` for a backtrace.


failures:
    utils::tests::example

test result: FAILED. 61 passed; 1 failed; 0 ignored; 0 measured