Add operators for ensuring wait condition stability

[sbergen]

Use case

In UI tests, you might wait for some larger part of the users actions to be completed once you return to the previous page. However, it's not too uncommon for there to be some indeterministic short periods where an underlying page will be shown for a brief moment (e.g. one frame), triggering a false completion. It would be nice to be able to add robustness by waiting for a condition to be true for some amount of frames, and possibly seconds.

Solution

Add operators on wait conditions:

• ToBeStableForFrames(int frames)
• ToBeStableForSeconds(double seconds)

So that you can do something like WaitForConditionOn(...).ToBeStableForFrames(2)