Abstract time away from ExecutionTime

#1076 abstracted time (Wait, Delay and more) to make testing DelegationAssertions reliable.

We should do the same for ExecutionTime.

[Evangelink]

@jnyrup I suspect that the problem is coming from the line 45 when executing !execution.Wait(rate);.

If you try to debug the test described here, you will end up with the following workflow:

1. Set result of the delayTask to true
2. Fake wait for 100ms (time given in the BeGreaterThan)
3. Return true, result that was set in #1
4. isRunning is now false so we stop the loop
5. We execute the assertion with the currently elapsed time
6. We fake sleep for 200ms
7. Test fails because 100ms not strictly greater than 100ms

[dennisdoomen]

I read from #1620 that you decided to keep using a real StopWatch for all remaining tests - I assume that’s to keep tests close to the actual executed paths?

Correct.

Would you prefer if I only made the same fix to When_the_execution_time_of_a_member_is_close_to_a_limit_it_should_not_throw as in #1620?

I think we should only fix the ones that tend to be unstable.