我们可以在板条箱之间共享测试实用程序吗?

问题描述

我的 crate-0 有 src/lib.rs 如下:

I have crate-0 that has src/lib.rs as follows:

#[cfg(test)]
pub mod test_utils {
    pub struct OnlyInTests(pub usize);
    pub fn helper() -> usize { 999 }

    #[test]
    fn test_0() { let _ = OnlyInTests(helper()); }
}

我也有 crate-1，我需要在 crate-0 中定义的测试框架:

I also have crate-1 where I need the testing framework I defined in crate-0:

extern crate crate_0;

#[cfg(test)]
pub mod test_utils {
    // This will error out - cannot find mod test_utils in crate_0
    use crate_0::test_utils::{OnlyInTests, helper()};

    #[test]
    fn test_1() { let _ = OnlyInTests(helper()); }
}

这里的代码很简单，可以复制粘贴，但实际上我有复杂的测试实用程序，我想在测试 crate-1 时使用.

The code here is trivial and can be copy-pasted, but in reality I have complex test utilities which I want to use while testing crate-1.

我无法将测试实用程序分离到不同的 crate 中，因为我会得到循环依赖错误:test_utils 将依赖于 crate-0 create stuff 和 crate-0 将依赖 test_utils 进行测试).我实际上也不想这样做，因为还有更多的 crate，我想在依赖 crate 中使用它们的测试实用程序.

I cannot separate out the test utilities into a different crate as I would get cyclic dependency error: test_utils would depend on crate-0 create stuff and crate-0 would depend on test_utils for testing). Nor do I actually want to do this as there are further crates down the line whose testing utilities I would like to use in dependent crates.

推荐答案

权衡明显不同的两种解决方案:

Two solutions with sightly different trade-offs:

将您的测试实用程序而不是您的测试放入一个新的 crate crate-0-testutils.使 crate-0 依赖于 crate-0-testutils；crate-0-testutils 依赖于 crate-0；crate-1 开发依赖于 crate-0-testutils 并依赖于 crate-0.

Put your test utilities but not your tests in a new crate crate-0-testutils.Make crate-0 dev-depend on crate-0-testutils; crate-0-testutils depend on crate-0; crate-1 dev-depend on crate-0-testutils and depend on crate-0.

这不会创建循环依赖，因为开发依赖不会被传播.由于开发依赖性，您在 crate-0 中的测试仍然可以使用 crate-0-testutils 中的内容.

This does not create a circular dependency as the dev-dependencies do not get propagated. Because of the dev-dependency your tests in crate-0 can still use what is in crate-0-testutils.

如果您的所有创建都具有此类实用程序，这最多会使您的 lib crate 数量增加一倍.

This at most doubles the number of your lib crates if all your creates had such utilities.

在crate-0的Cargo.toml中创建一个不依赖任何东西的特征:

Create a feature in the Cargo.toml ofcrate-0 that does not depend on anything:

[features]
testing = []

crate-1 中的一个依赖于上述内容:

And one in crate-1 that depends on the above:

testing = ["crate-0/testing"]

然后在未启用该功能时对每个板条箱进行第一次测试失败，以便更容易理解错误:

Then make the first tests on each of the crates fail when the feature is not enabled, to make for an easier to understand error:

#[cfg(all(not(feature = "testing"),test))]
mod testusage {
    #[test]
    fn panic_without_testing_feature() {
        panic!("Please use the feature testing when running tests.\n\nUse: cargo test --features testing\n\n");
    }
}

仅在通过为其添加保护而启用该功能时编译实用程序:

Only compile the utilities when the feature is enabled by adding a guard for it:

#[cfg(feature = "testing")]
fn testing_utility() {
}

这只会在每个 crate 中添加一个功能，而不管它依赖多少测试功能，但缺点是需要对测试进行特殊调用.

This only adds one feature in each crate regardless of how many testing features it depends on but has the downside of needing a special invocation of the tests.

避免在任何 crate 范围的依赖声明中添加此功能.在 crate-1 的 dev-dependency 中包含来自 crate-0 的测试功能，其中 crate-1 也有一个对 crate-1 的正常依赖即使在发布模式下，code>crate-0 也会生成具有该功能的货物构建 crate-0，即使对于 crate-1 的构建目标也是如此.

Avoid adding this feature in any crate wide dependency declaration. Including the testing-feature from crate-0 in the dev-dependency of crate-1 where crate-1 also has a normal dependency on crate-0 results in cargo building crate-0 with that feature even for the build target of crate-1 even in release mode.

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