Almost all of lifecycle event tests are based on the following assumption: all 
the listeners must finish processing events before servlet can continue its own 
execution. All these tests have the same model: listeners and servlets exchange 
information through static arraylist which is filled up by listener and then 
processed by servlet. I couldn't find any requirement in Sun servlet spec 2.3 
on the synchronization between listener and the entity which initiated the 
process of adding/removing attribute from anywhere. There are requirement 
on .valueBound()/.valueUnbound() methods and on startup/shutdown events but 
nothing on attributeAdded/Removed/Replaced() etc.
This is my undestanding and this could be wrong so I would really appreciate it 
if you could keep me posted on this.