[flexcoders] newbie question on synchronous and asynchronous events

[Dan]

>From Flex cookbook beta on adobe.com, "How to handle events in a 
TestCase?" article:
"Testing behavior in a TestCase often involves waiting for 
asynchronous events. If the TestCase methods only concern synchronous 
events like property change events fired immediately when the property 
is set, no special handling is required. It is only when asynchronous 
events are involved that extra care needs to be taken. A common 
example would be waiting for a URLLoad to finish or a UIComponent to 
finish creation."

My question is: How do I distinguish between the synchronous and 
asynchronous  events? 
>From what is said, if the event is synchronous, then I could test for 
event effect in synchronous manner. For example: 

public function testSync(){
        this.myValue = 0
        addEventListener(MySynch.Sync, listener)
        dispatchEvent(new MySynch)
        assertEquals (this.myValue, 10) 
}

public function listener(){
        this.myValue = 10
}


Now, if I write the code for WebService send, test code would not 
work. Am I getting this right? If so, how do I distinguish between the 
synchronous and asynchronous  events? 

Thanks, 

Dan