> Correct. But how are you testing that you successfully crash

In a language like rust, failed assertions panic. And panics generally aren't "caught".

> instead of corrupting on-disk data stores

If your code interacts with the filesystem or the network, you never know when a network cable will be cut or power will go out anyway. You're always going to need testing for inconvenient crashes.

IMO, the best way to do this is by stubbing out the filesystem and then using randomised testing to verify that no matter what the program does, it can still successfully open any written (or partially written) data. Its not easy to write tests like that, but if you actually want a reliable system they're worth their weight in gold.

You don't. Assertions are assumptions. You don't explicitly write recovery paths for individual assumptions being wrong. Even if you wanted to, you probably wouldn't have a sensible recovery in the general case (what will you do when the enum that had 3 options suddenly comes in with a value 1000?).

I don't think any C programmer (where assert() is just debug_assert!() and there is no assert!()) is writing code like:

    assert(arr_len > 5);
    if (arr_len <= 5) {
        // do something
    }

They just assume that the assertion holds and hope that some thing would crash later and provide info for debugging if it didn't.