No, I've had great experiences with assertions in code. People have paid my salary because the assertions are invalid and cause more problems than they solved. :D
> Failing an assert in production of course sucks and is costly. But what is more costly is letting the bug slip through and cause hard to diagnose bugs, program incorrectness and even (in some cases) silent address space corruption that will then manifest itself in all kinds of weird issues later on during the program run.
The direct counterpoint to this is that:
Any assertion that validates a runtime invariant can (and IMO should) be converted into a test which covers that same invariant, with coverage information proved by tooling.
This is possible unless the underlying design of the system under test is such that it prevents adequate testing, or your approach to testing is lacking. If you have those problems then asserts are a band-aid on broken practices. Moving quality checks to the left (design / compile time, not runtime) is a generally beneficial practice.
Put another way, I've seen many bugs which should have been caught cheaply early with adequate testing practice, rather than at runtime where they caused system failures. It's a rare bug that I see that that isn't the case.
Perhaps there are points where this broad recommendation doesn't apply. Safety engineering might be one of those, but the problem space of selling someone a widget over the internet rarely has that same level of need for runtime invariant testing that sending a rocket to space might.
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On a different side of this, I do think that system level assertions (i.e. real code paths that result in actions not `debug_assert!` calls which result in crashing) can belong in systems to check that some process has reached a specific state. I prefer systems to be designed that don't (provably) crash ever.
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A third side to this is that assertions are code too. They are a place which is rarely if ever tested (and is generally impossible to test because they cover invariants). This means that they're an unmitigatable risk to your system.
A thought experiment for you, what if LeftPad[1] (instead of being deleted) added an assertion that the total number of characters was < 10. Removal caused a bunch of pain for devs. Assuming that this change rolled out through development chains as normal, this change would have broken many runtime systems, and would have been much more costly.
