xample may help here: Let's say a user clicks two buttons, one after another
and both load data from different servers. They take different times to respond.</p>
<p>When writing your tests, you need to be keenly aware of the fact that you cannot
be sure that the response will return immediately after you make your requests,
therefore your assertion code (the "tester") needs to wait for the thing being
tested (the "testee") to be in a synchronized state. In the example above, that
would be when both servers 