If unit tests are being done, some kind of emulator is usually what gets used and the scope of testing is significantly limited.

The more common approach is to abandon unit tests all together and go for board functional tests where as many of the external interfaces are controlled and put through representative loads. The complexity of the software is rarely that high so we can be pretty confident that we’re covering everything we need to care about anyways.

There’s a couple big reasons, sometimes you only have to deal with one or two, other times you’re hit with all of them.

The data source for the algorithms often comes from arbitrary memory addresses that live outside the context of the C, C++, or Rust runtime. If I want to read CPU core temp I send magic numbers to one address to configure ADC channel conversion, another magic number somewhere else to do the conversion, wait a few dozen microseconds, then read a third new address that I squint one eye, spin around 10 times, and do a handstand and I’ll get a number that looks like temperature.

If I’m running on the microcontroller, I’m essentially in production environment and I can’t control what the data is. If I recompile for a different system (say x86 Linux) then I’m almost certainly going to segfault. I could abstract out the reading of the data, but then on my tiny 8MHz microcontroller that has to run it’s main loop at 1000Hz, I only have a few thousand clock cycles to get everything done, calling functions, pushing/popping the stack takes a lot of time.

Adding to the pile-on most microcontrollers have <1MB of RAM, many in the tens of kilobytes range so I don’t have much of a stack to work with and I need to keep even the number of instructions down.

Even if you do all the abstractions, you then have extra logic you have to write to simulate what is happening and subtle behaviors that are timing dependant. It frequently is extremely difficult to do that as the documentation rarely fully describes everything, so you can lull yourself into a false sense of security that you’ve tested the code and it’s correct, but then you get stuck on a register value that never changes and a watchdog timer comes along and resets the hardware on you.

And that’s not the getting into the runtime or build environments, flashing procedures, limited flash cycles, and a million other business constraints that technically you can do it, but at that point your dev team has all taken the month off to go play Half Life 3

I guess I don’t really count skimming as reading haha

When looking for readability, maintainability, etc what I mainly look for are design patterns. If you’re using the same boilerplate and layout I’m going to start skipping over sections

I also mainly work on high performance embedded systems that are difficult/nearly impossible to unit test and I dont always have line coverage metrics. A lot more verification by inspection in my corner of the world

I’d argue that Monte Carlo is a bad example here, and is an example of a deterministic tool.

You use a tool to create an outcome, you’re looking for an answer or a solution that you can trust.

If you want to examine behavior of a system that has input variables across some known range, you could brute force it, try every single possible combination and wait a millennia. Or you use a monte carlo strategy, let randomness enter the simulation to build out a basic characterization. You want more detail? More confidence? Increase the number of runs. I can trust that if I increase the number of runs I gain higher fidelity, if the tool/strategy was non deterministic I couldn’t do that

Not parent commenter, but no, not to the same degree.

The level of trust I have in a source greatly changes how I review it. If I know that I’m reviewing code from a competent developer, I’m going to see a for loop and look for why is this here, how does it play into the larger objective and if I’m happy with it, I move on. But if I don’t trust the developer as much, I’m looking at far more like what data type is being used in the indexing, what’s the break condition, can go off the rails into random memory.