The coverage-helper::test doesn't work with tokio::test

[Phoenix500526]

Hi, @taiki-e.

Currently, the implementation of coverage_helper replaces std::test with coverage_helper::test. However, this approach doesn't work for tokio::test. Given that tokio::test is widely used, shall we support tokio::test in this crate?

IMO, we can provide a tokio module in coverage_helper, like:

mod test{
    use coverage_helper::{tokio, test};
    #[test]
    fn test_foo() {...}

    #[tokio::test]
    async fn test_bar() {...}
}

What do you think? If this approach is feasible, I can do some contributions.

[taiki-e]

As said in taiki-e/cargo-llvm-cov#273, tokio::test refers ::core::prelude::v1::test, so it's not working with coverage_helper.

The most desirable fix is to change libtest so that the test attribute gets no_coverage, and the second most desirable is to make the change on the tokio side.

[taiki-e]

This problem may have been resolved by tokio-macros 2.3.0, which includes tokio-rs/tokio#6497.

[gmli]

And so, what are we supposed to write in the tests using #[tokio::test] ?

EDIT : ok I understand, the version 2.3.0 of tokio-macros may have solved it without any change. I’ve updated to tokio 1.40.0 and the problem remains.

[bitcapybara]

any update?

[taiki-e]

No update on this issue, but the #[coverage] attribute itself has been improved and I believe most of the use cases for this crate will be replaced by it: taiki-e/cargo-llvm-cov#123 (comment)

[taiki-e]

#[coverage(off)] attribute has been stabilized in rust-lang/rust#130766 (will be included in Rust 1.85).

I will deprecate coverage-helper in favor of the pattern that is now documented in cargo-llvm-cov: taiki-e/cargo-llvm-cov#123 (comment)

If you want to ignore all #[test]-related code, you can use module-level #[coverage(off)] attribute:

#[cfg(test)]
#[cfg_attr(coverage, coverage(off))]
mod tests {
    // ...
}

cargo-llvm-cov excludes code contained in the directory named tests from the report by default, so you can also use it instead of #[coverage(off)] attribute.