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Next I'm going to go over some of the XP's values

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and principles that I just hinted on earlier in the lesson.

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The first one, the first important value is communication. There

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is no good project without good communication. And XP tries to

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keep the right communication flowing and it uses several practices

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to do that. It's got practices based on and require information

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and in general share the information. For example, pair programming.

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And we're going to say more about that. User stories, customer involvement,

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all activities that help communication,

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that faster communication. Another important

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principle that we already saw, is simplicity. And the motto here

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is live for today without worrying too much about the

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future. When you have to do something, look for the simplest

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thing that works. And the emphasis here is on, that

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works. We want to build something simple, but not something stupid.

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Feedback. That's extremely important in XP, and it occurs at

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different levels, and it is used to drive changes. For example,

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developers write test cases. And that's immediate feedback. If your test cases

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fail, there's something wrong with the code. Or there's something that you

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still haven't developed. Developers also estimate new stories right away as soon

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as they get them from the customers and that's immediate feedback to

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the customer. And finally, on a slightly longer time frame, customers and

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tester develop together functional system test

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cases to assess the overall system.

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And also in this case, that's a great way to provide feedback

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and by the way, also to help communication. And finally, courage, the courage

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to throw away code if it doesn't work. To change it if you

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find a way to improve it. To fix it if you find a problem.

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To try out new things if you think that they might work better

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than what you have right now. Now, that we can build and test systems

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very quickly, we can be much braver than what we were before. So

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how do we accomplish all that? And what are XP's practices that are going to

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help us follow these principles and adhere to those values? These are some

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of XP practices. There are more, but those are the ones that I'd like

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to discuss in a little more depth, individually. Incremental planning,

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small releases, simple design, test first, refactoring. We will actually

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have a whole lesson next on refactoring. Pair programming, continuous

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integration, and on-site customer. So let's start with incremental planning.