assertsion failure hangs instead of reporting failure

[psusi2]

I excitedly added defmt-test to my project when I found it and initially cargo test happily ran my unit tests in the target. But then I added a new test where an assert!() failed, and instead of reporting the failure, it just hangs. Before I found defmt I was just calling the unit tests myself from main and a failure reported the panic with defmt. Also I am using embassy on an STM32U535RETx.

[psusi2]

Things get even stranger now. I found https://github.com/knurling-rs/app-template/blob/main/src/lib.rs and it shows to install a hardfault handler and a panic handler. The panic handler appears to be dead code ( nothing ever calls it ). The hardfault handler let cargo test exit instead of hanging, but instead of printing that there was a panic due to assertion failure, it prints a backtrace that only shows 3 frames in cortex-m-semihosting, and then Error: Semihosting indicates exit with reason: 0x20023.

I found instructions to set up vscode to debug the test program and get the defmt output here: https://probe.rs/docs/tools/debugger/.

When I run the test program this way, it DOES print the panic assertion failure and not the backtrace, and doesn't care whether the hardfault handler is there or not.