Problems testing in a no_std environment (Arduino)

[tsettles]

Hey all, I'm new here (and to rust)

I recently got an Arduino robot that I'm trying to program. I want to use rust to test my code on my own computer, not just run it on the Arduino. However, I've been having quite the time running tests.

I generated the project based off of Rahix's template, and when I run cargo test I get a bunch of errors like:

error[E0277]: the size for values of type `core::cmp::Ordering` cannot be known at compilation time
   --> /Users/tws/.cargo/registry/src/github.com-1ecc6299db9ec823/nb-1.0.0/src/lib.rs:198:38
    |
198 | #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
    |                                      ^^^^^^^^^^ doesn't have a size known at compile-time
    |
    = help: the trait `Sized` is not implemented for `core::cmp::Ordering`
note: required by a bound in `Option`
   --> /Users/tws/.rustup/toolchains/nightly-2022-06-13-x86_64-apple-darwin/lib/rustlib/src/rust/library/core/src/option.rs:518:17
    |
518 | pub enum Option<T> {
    |                 ^ required by this bound in `Option`
    = note: this error originates in the derive macro `PartialOrd` (in Nightly builds, run with -Z macro-backtrace for more info)

I am running a nightly version of rust, as that seems to be required. I've tried defining the tests in a module in the same lib.rs file, in a separate file, and in a separate workspace, but I always get error like the one above.

I am able to run the code fine on the arduino, but I can't run tests. My code is at this repo, if that helps give some more context.

Edit:
The tests I am trying to run are as simple as

#[cfg(test)]
mod testing {
    #[test]
    fn foo() {
        assert_eq!(1 + 1, 2);
    }
}

[Coding-Badly]

Independent of the error you're getting, do the Arduino crates you're using have support for running tests on a PC? Or even building for a PC?

When building for the target, code has to be generated that interacts with the AVR peripherals (I/O machine instructions specific to that processor). If an alternative is not written for a PC you could actually end up with what is essentially a corrupt executable.

[tsettles]

I've done a bit of searching through the repo, and haven't found any mentions of tests. The tests I'm trying to write don't depend on any I/O, or anything from the crate directly, so I would expect that with the right settings they could run. How can I set up my tests to target my PC, while my builds still target the avr/adruino?

[Coding-Badly]

Step 1: Pick one thing you want to unit test. What is that one thing?

[tsettles]

Thanks for helping!
So far, it's a custom sine function that operates on i8 and returns i8, instead of floats. There is nothing in there that should tie it to any particular OS/platform, so that should be a good place to start.
https://github.com/roboteng/rust-mechanum/blob/4b3104b035a2c4d12f6f4e947f36a2f320446bc7/src/lib.rs#L176

[Coding-Badly]

Yup. That definitely should be portable.

Were I in your shoes step 2 would be: Move the code of interest (sin) to a new crate. This new crate will contain things that are portable and, more importantly, unit testable.

Step 3 would be to reference the new crate from the old crate. That's really easy to do if the two crates are peers (side-by-side in the directory structure), together in a workspace, have a parent-child relationship in the directory structure, or one of them is published on crates.io. I prefer peers in a workspace when a project is young. Though, for this situation, a workspace may make things more difficult. And, you can always introduce the workspace later. So, peers.

I do wonder if the Libc sin is a better choice. That's an awful lot of 32 bit integer multiplies. For floats (f32) on AVR processors multiply and divide are actually faster (24 bits vs 32 bits).

[tsettles]

Thanks for all the help! After following some of your steps, I get:

error: ran out of registers during register allocation

error: could not compile `core` due to previous error

So I think I've got some other errors to work through. I ended up finding this blog post, so I'm going to try and follow this, and see where I get. It looks like it's trying to solve the exact problems I have.

[Coding-Badly]

Bummer.

Did you get the error when building for the AVR processor?