> Why don't just learn algorithms and other computer science "direct" approach by analysing problem and solving it in most efficient way? --- The problem ofte

> Why don't just learn algorithms and other computer science "direct" approach by analysing problem and solving it in most efficient way? --- The problem often isn't clearly defined. To a certain extent programming is an exploration of the problem until you're in a position to go 'And so...' Add to that, that knowledge of the context and lower level abstraction layer that your algorithm corresponds to is imperfect. (Imagine doing maths where a malicious demon sometimes changes the contents of variables on you according to a set of rules that you don't know.) As such, any algorithm that someone wrote while trying to express the problem and provide a solution may or may not do what they expect it to when given in any particular language on any particular machine. There are a couple of ways to try to address some of the difficulties with that. One is to write code at such a low level that you can be sure of the blocks you're using. Another is to try to climb the abstraction layers using a language with certain safeties built in to try to limit the context you have to be aware of. But there are drawbacks with both of those methods, and testing is a way to deal with the inevitable oversights involved. (It's also good in getting people to more tightly define the problem in the first place for you. Acceptance tests are a wonderful thing sometimes.)