Originally by @Legioth

Yes, we are familiar with this phenomenon. Teemu was doing something about this for some of our internal tests some weeks ago, but I don't remember whether the root issue was actually fixed or just temporarily workarounded by adding delays to our tests.

Originally by @Artur-

client.isActive() does not necessarily wait for rendering to complete but for no active server communication to take place. Typically these kind of issues can be worked around by waiting for some element to be present before interacting with it. Not sure how QFTest works but a communication error would never be expected by TestBench at least, provided that client.isActive() returned false.

This sounds a bit like the same problem that causes our LayoutTesterApplication to sporadically capture incorrect screenshots. On the other hand, that is only a screenshot comparison issue, it does not cause communication error.

Originally by @Saulis

Let's create a interface (Jonatan will provide nice naming for us) that can be used to ask a client component if it has any pending actions going on. Then, the ApplicationConnection should use this interface in it's isActive() method.

Originally by @Artur-

This could be

/** Gives widgets the possibility to indicate to the framework that there is work  
 - scheduled to be executed in the near future and that the framework should wait 
 - for this work to complete before assuming the UI has reached a steady state.
*/
public interface DeferredWorker {
    /** @returns true, if there are operations pending which must be executed before reaching a steady state */
    public boolean isWorkPending();
]

Originally by @Artur-

In what way is this pending design?

Originally by Markus Koivisto

https://dev.vaadin.com/review/#/c/4152/