How Do You Run HIL Tests on ESP32 Original Without additional hardware?

[bowen951209]

Hello. New to embedded development here.

I've got an ESP32 original version and want to run some hardware-in-loop(HIL) tests.
The suggested framework is `embedded-test` in [The Rust on ESP Book](https://docs.espressif.com/projects/rus ... sting.html). However, it seems like it is only available with `probe-rs` backend and requires a USB-Serial-JTAG port, which is not available on my ESP32 orginal devboard. Looks like you can use `probe-rs` if you have a `ESP-Prog` hardware. But I'm not dealing with breakpoints, and I currently don't own a `ESP-Prog`, so I'm exploring solutions with the default USB port.

I've managed to *naively* run HIL tests by collecting test functions with [linkme crate](https://github.com/dtolnay/linkme), and run them in another binary. I know this solution is dirty. I would have to build the entire crate, and for example, if I'm using `esp-radio` in my crate but not in tests, I still have to initialize RTOS in the test binary's main function.

So how would you guys suggest to run HIL tests without `probe-rs`? And is it possible for `embedded-test` to support [espflash](https://github.com/esp-rs/espflash) in the future?