Use of Shuttle for Rust async and #[tokio::main]

[cameronelliott]

Hi, I am very interested in what Shuttle brings to the table for testing.
As far as I can tell it is mostly designed for Rust sync code without #[tokio::main] main setups.

But I am a bit confused by the presences of the shuttle::future module.
I am guessing it's really for sync programs which are invoking a little bit of async code?

It seems like if Shuttle was intended for testing mostly async programs, there would
be replacement implementations for stuff like tokio::sync::Mutex (An asynchronous Mutex-like type).

Anyway I'd like to get some feedback about the suitability of Shuttle for testing mostly async functions and code.

Thank you. And thank you for creating Shuttle.

[jorajeev]

Shuttle does support checking async code; for instance you can find examples of checking code with mpsc channels from the futures crate in our tests.

To support code using libraries like tokio, there are two options: (1) recompile tokio code using Shuttle primitives (which, as you can imagine, is a lot of work and hard to maintain long-term), or (2) write your own replacements for tokio primitives in Shuttle (similar to how we've written replacements for std::sync primitives in the shuttle::sync module). We've done some early work on (2), but don't have anything ready to publish at the moment.