你如何能够测试所有的问题？你没有遇到组合爆炸吗？
It’s true that computation theory pretty much proves you can’t validate every possible state of a non-trivial system. However, in practice, an experience programmer can produce a pretty good set of tests that will result in a high degree of confidence that the system is working correctly.计算理论很好的证明了对一个非平凡系统你不可能核实它的所有的可能的状态。当然在实际中，一个有经验的程序员能够给出一个相当不错的测试集，通过测试的系统能够获得更高的正确运行的信任程度。
It’s sort of like those probabilistic tests used to produce large prime numbers for public-key cryptography. You can’t tell for certain that a number is prime without trying to factor it, but youcan apply a number of simpler tests that will verify its primeness to any degree of certainty that you want.这类似于那些用来为公开密匙系统产生大质数的概率测试。你不能没有试着分解某个数就肯定地说这个数是质数，但是你可以使用大量的简单测试在某种你需要的程度上确认它是质数。

难道简单设计不会使你的程序不能很好地扩展吗？
Simple design, practiced alone typically would have this result. But XP says that after you do the simplest thing that could possibly work, you go back and refactor your code until everything your code needs to express appears once and only once within the code base.只使用简单设计通常确实会产生这种结果。但是XP说的是，在你的作了最简单的能够工作的东西后，你回去求精你的代码直到你的代码所要表达的所有事情在你的代码库中出现且只出现一次。

难道YAGNI不会引导你沿着没有出路的设计道路走下去吗？
General experience in the XP community is an unqualified “no”. At the very worst, it may happen, but so rarely that your wins from all the other YAGNIs will more than pay for having to backtrack once in a while. XP社会的普遍经验认为这绝对不可能。虽然在最坏情况下，这是可能的，但你从所有其它的YAGNI那里赢来的价值很少会超过你为偶尔的倒退所做的付出。

I don’t think I [want to do/can sell my bosses on doing] all of the practices. Can I leave some out and still be doing XP?我觉得我没法[实施或者能让我老板接受]做所有XP实践。我能只做其中一些而仍被称为是XP吗？Many of the practices work well in isolation, so it’s quite possible you’d be better off using the ones you feel like than none at all. However there’s a synergistic effect to using all of them together
that you’ll be missing out on. As a result, a lot of people in the XP community feel strongly that if you’re not using all 12 practices, you’re not doing XP.大部分实践都能够独自的很好的工作，所以你使用其中一些肯定会比什么都不用会使你有更好的境况。然而，将所有的实践配合在一起使用会有更好的效果。XP社会的许多人强烈认为如果你没有用到所有的12个实践，你就不是在做XP。

As a practical matter, there’s currently no XP certification authority. You can do whatever you want, and no XP Gestapo is going to kick in your door. But if you’re not using all 12 practices, you probably could be going faster.一个实际的情况是目前没有一个XP的权威认证。你可以随便做你想做的，没有XP的盖世太保来敲你的门。但是如果你没有使用所有的12个实践，你可能会走得更快。

在哪儿我能学到更多的XP的知识？
The best place to start is currently Kent Beck’s book “Extreme Programming Explained: Embracing Change”, (available from Amazon.com among other places). This book is essentially the definitive guide to XP at the moment, and a fairly quick read.目前最好的起点是Kent Beck的书：《Extreme Programming Explained: Embracing Change》（可以从Amazon.com或其他地方获得。）这本书是现在权威的XP指南，也是一本很容易读的书。
Once you have an overview of XP, visit Ward Cunningham’s Wiki Wiki Web (or Wiki for short). Wiki is a simple, yet powerful hypertext system. Anyone can add or modify any page on Wiki, so the system collects the knowledge of thousands of people into a (semi) coherent whole. Started as a system for cataloging Design Patterns, Wiki has grown to include literally hundreds of pages related to XP. A good starting point is  http://c2.com/cgi/wiki?ExtremeProgrammingRoadmap.一旦你有了一个XP的总体概念，请访问Ward Cunningham的Wiki Wiki Web（简称Wiki）。Wiki是一个简单的但功能强大的超文本系统。任何人能增加或修改它上面的任何页面。这样，该系统集中了数千人的知识于一个（半）连贯的整体之中。从一个设计模式的目录系统，Wiki已经成长为包含了数百页XP相关页面的系统。可以从这里开始：  http://c2.com/cgi/wiki?ExtremeProgrammingRoadmap.