1. One must either encode the assumption into a precondition or transfer the incoming data into a sorted data structure. But the gist is to always validate assumptions.

2. RAII’s pretty good at handling resources. Then one can inject failures to test the error handling paths and combine with code coverage measurements.

3. That sounds like an issue in the wider system which may be handled in the subsystem under development assuming that it can throttle back its requests, drop them, etc. But it may just as well be handled in another part of the larger system. It belongs more to the architecture realm, but it’s absolutely possible to foresee such issues.