Add #[async_test] to futures-test crate?

[ngg]

Hi!

I'm interested what you're thinking about adding an #[async_test] proc-macro to the futures-test crate.

There were previous discussions about it at #1169 (comment) and there are also some implementations existing already.

• I have a kind of ugly (sry but I'm not good at proc-macros) but working implementation at futures-await-test-preview which uses futures_executor::LocalPool::new().run_until(), I'm not sure if this is better or worse then using block_on, for my use-cases it seems to work perfectly.
• There is one created for tokio: tokio-async-await-test

Examples for intended use-case:

#[async_test]
async fn normal_test() {
    assert!(create_future().await == 4);
}

#[async_test]
#[should_panic]
async fn panic_test() {
    assert!(create_future().await == 5);
}

#[async_test]
async fn result_test() -> Result<(), ()> {
    assert!(create_result_future().await? == 4);
    Ok(())
}

Currently I use my implementation to write tests for a Rust wrapper around an asynchronous C++ library, which uses only futures-0.3, not tokio. I find it really useful, perhaps others would too even if it uses futures-executor only at first. Later it could be somehow extended to support other executors as well..

Would you be interested in adding something like this to futures-test?

[LucioFranco]

@ngg tokio currently has one https://docs.rs/tokio/0.2.0-alpha.5/tokio/attr.test.html