I looked it up yesterday and they have the ECU in the loop for the driving simulators (the ones the drivers practice with and that are used for checking mechanical changes). But these use empirical models, they can't simulate everything. You would have to get a lot right in the models and top of that know where to test edge cases and then simulate all inputs correctly for those. You can surely input yesterday's weather conditions but whatever model is there might not predict an output that goes to the next model and so on..

I'm sure there's also all kinds of other HIL testing but it comes down to thinking about all conditions and having models and tests that are realistic enough for those conditions. It's impossible to have perfect coverage.

It's probably kind of lucky that enough cars were impacted so that the issue was revealed instead of having a just a few cars knocked out of the race.