What is Testing + how much is enough?

Since I wrote about bugs last post it's natural to move on to the question 'What is Testing?'.


Software testing is an objective investigation into a software or computer system before it is implemented in order to see if it meets all of it's expectations and is ready to be released or not.


The reason the software developers don't test their products is mainly because of the lack of objectivity, and they may not want to find anything wrong with their creation on a subconscious level.


Thought finding bugs is what testers do the tester's job is not to prove that a software is full of problems but if the system meet's all of the client's expectations.  No matter how much test a tester will do there will always be bugs that will escape the tester's eyes.  The ISTQB book Foundations of Software Testing briefly explains that exhaustive testing is impossible, meaning that it is impossible to detect every single bug for multiple reasons. 
I may post an article later on reasons why exhaustive testing is impossible but there are a few main reasons. Main reasons include the fact that the testers will not always be able to test the software in the same way ordinary user would, There isn't enough time or resources to test everything, and that the bugs may exist in areas that the customer didn't feel needed testing as they were unimportant (ex: grammar/spelling).


Finally in terms of how much testing is enough that question has no definite answer and it is in fact mostly determined by how much time and money that the client has given you, and even this can vary greatly from client to client.