need of a Testing

If the developers develop the S/W and it release to 
customer,then if he faces any problem it decreases the 
company impression, to overcome above problem, the company 
people are consontrating on testing also to estimate 
completeness, correctness and user friendlyness of that 
software. 

if the developers tested the build they think only in 
positive manner, because they developed the software if 
other tester tests that software then they tests that in 
all stages with respective user, functionality and speed of 
the software also to release a good product or a new s/W to 
market or client. 

without testing released may contains at lease some errors 
to over come those testing is mandatory.