The two big problems seem to be concurrency (always a problem) and state, which immediately suggest that making things as functional as possible would help a lot.
Ideally all state that's used in a test would be reset to a known value at or before the start of the test, but this is quite hard for external non-mocked databases, clocks and so on.
For integration tests, do you run in a controllable "safe" environment and risk false-passes, or an environment as close as possible to production and risk intermittent failure?
A variant I've seen is "compiled languages may re-order floating point calculations between builds resulting in different answers", which is extremely annoying to deal with especially when you can't just epsilon it away.
Ideally all state that's used in a test would be reset to a known value at or before the start of the test, but this is quite hard for external non-mocked databases, clocks and so on.
For integration tests, do you run in a controllable "safe" environment and risk false-passes, or an environment as close as possible to production and risk intermittent failure?
A variant I've seen is "compiled languages may re-order floating point calculations between builds resulting in different answers", which is extremely annoying to deal with especially when you can't just epsilon it away.