rust test

单元测试

测试（test）是这样一种 Rust 函数：它保证其他部分的代码按照所希望的行为正常 运行。测试函数的函数体通常会进行一些配置，运行我们想要测试的代码，然后 断言（assert）结果是不是我们所期望的。

大多数单元测试都会被放到一个叫 tests 的、带有 #[cfg(test)] 属性 的模块中，测试函数要加上 #[test] 属性。

当测试函数中有什么东西 panic 了，测试就失败。有一些这方面的 辅助宏：

• assert!(expression) - 如果表达式的值是 false 则 panic。
• assert_eq!(left, right) 和 assert_ne!(left, right) - 检验左右两边是否 相等/不等。

 

pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

// 这个加法函数写得很差，本例中我们会使它失败。
#[allow(dead_code)]
fn bad_add(a: i32, b: i32) -> i32 {
    a - b
}

#[cfg(test)]
mod tests {
    // 注意这个惯用法：在 tests 模块中，从外部作用域导入所有名字。
    use super::*;

    #[test]
    fn test_add() {
        assert_eq!(add(1, 2), 3);
    }

    #[test]
    fn test_bad_add() {
        // 这个断言会导致测试失败。注意私有的函数也可以被测试！
        assert_eq!(bad_add(1, 2), 3);
    }
}

可以使用 cargo test 来运行测试。

 

$ cargo test

running 2 tests
test tests::test_bad_add ... FAILED
test tests::test_add ... ok

failures:

---- tests::test_bad_add stdout ----
        thread 'tests::test_bad_add' panicked at 'assertion failed: `(left == right)`
  left: `-1`,
 right: `3`', src/lib.rs:21:8
note: Run with `RUST_BACKTRACE=1` for a backtrace.


failures:
    tests::test_bad_add

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

测试 panic

一些函数应当在特定条件下 panic。为测试这种行为，请使用 #[should_panic] 属性。这 个属性接受可选参数 expected = 以指定 panic 时的消息。如果你的函数能以多种方式 panic，这个属性就保证了你在测试的确实是所指定的 panic。

 

pub fn divide_non_zero_result(a: u32, b: u32) -> u32 {
    if b == 0 {
        panic!("Divide-by-zero error");
    } else if a < b {
        panic!("Divide result is zero");
    }
    a / b
}

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

    #[test]
    fn test_divide() {
        assert_eq!(divide_non_zero_result(10, 2), 5);
    }

    #[test]
    #[should_panic]
    fn test_any_panic() {
        divide_non_zero_result(1, 0);
    }

    #[test]
    #[should_panic(expected = "Divide result is zero")]
    fn test_specific_panic() {
        divide_non_zero_result(1, 10);
    }
}

运行这些测试会输出：

 

$ cargo test

running 3 tests
test tests::test_any_panic ... ok
test tests::test_divide ... ok
test tests::test_specific_panic ... ok

test result: ok. 3 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

   Doc-tests tmp-test-should-panic

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

运行特定的测试

要运行特定的测试，只要把测试名称传给 cargo test 命令就可以了。

 

$ cargo test test_any_panic
running 1 test
test tests::test_any_panic ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 2 filtered out

   Doc-tests tmp-test-should-panic

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

要运行多个测试，可以仅指定测试名称中的一部分，用它来匹配所有要运行的测试。

 

$ cargo test panic
running 2 tests
test tests::test_any_panic ... ok
test tests::test_specific_panic ... ok

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 1 filtered out

   Doc-tests tmp-test-should-panic

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

[root@bogon test2]# cargo test -- --ignored test_specific_panic  test_divide
    Finished test [unoptimized + debuginfo] target(s) in 0.01s
     Running target/debug/deps/hello_world-3a5299c9711119cc

running 0 tests

test result: ok$<2>. 0 passed; 0 failed; 0 ignored; 0 measured; 3 filtered out

[root@bogon test2]# 

忽略测试

可以把属性 #[ignore] 赋予测试以排除某些测试，或者使用 cargo test -- --ignored 命令来运行它们。

 

pub fn add(a: i32, b: i32) -> i32 {
    a + b
}

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

    #[test]
    fn test_add() {
        assert_eq!(add(2, 2), 4);
    }

    #[test]
    fn test_add_hundred() {
        assert_eq!(add(100, 2), 102);
        assert_eq!(add(2, 100), 102);
    }

    #[test]
    #[ignore]
    fn ignored_test() {
        assert_eq!(add(0, 0), 0);
    }
}

 

$ cargo test
running 1 test
test tests::ignored_test ... ignored

test result: ok. 0 passed; 0 failed; 1 ignored; 0 measured; 0 filtered out

   Doc-tests tmp-ignore

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

$ cargo test -- --ignored
running 1 test
test tests::ignored_test ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

   Doc-tests tmp-ignore

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out