Java4Android之单元测试入门

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本文主要介绍了如何使用 JUnit 4 提供的各种功能开展有效的单元测试，并通过一个实例演示了如何使用 Ant 执行自动化的单元测试。本文假设读者对 Eclipse 下进行 Java 开发有一定的经验，并了解 Java 5 中的注解（annotation）特性。
引言

毋庸置疑，程序员要对自己编写的代码负责，您不仅要保证它能通过编译，正常地运行，而且要满足需求和设计预期的效果。单元测试正是验证代码行为是否满足预期的有效手段之一。但不可否认，做测试是件很枯燥无趣的事情，而一遍又一遍的测试则更是让人生畏的工作。幸运的是，单元测试工具 JUnit 使这一切变得简单艺术起来。

JUnit 是 Java 社区中知名度最高的单元测试工具。它诞生于 1997 年，由 Erich Gamma 和 Kent Beck 共同开发完成。其中 Erich Gamma 是经典著作《设计模式：可复用面向对象软件的基础》一书的作者之一，并在 Eclipse 中有很大的贡献；Kent Beck 则是一位极限编程（XP）方面的专家和先驱。

麻雀虽小，五脏俱全。JUnit 设计的非常小巧，但是功能却非常强大。Martin Fowler 如此评价 JUnit：在软件开发领域，从来就没有如此少的代码起到了如此重要的作用。它大大简化了开发人员执行单元测试的难度，特别是 JUnit 4 使用 Java 5 中的注解（annotation）使测试变得更加简单。

JUnit 4 初体验

在开始体验 JUnit 4 之前，我们需要以下软件的支持：

Eclipse：最为流行的 IDE，它全面集成了 JUnit，并从版本 3.2 开始支持 JUnit 4。当然 JUnit 并不依赖于任何 IDE。您可以从 http://www.eclipse.org/ 上下载最新的 Eclipse 版本。
Ant：基于 Java 的开源构建工具，您可以在 http://ant.apache.org/ 上得到最新的版本和丰富的文档。Eclipse 中已经集成了 Ant，但是在撰写本文时，Eclipse 使用的 Ant 版本较低（必需 1.7 或者以上版本），不能很好的支持 JUnit 4。
JUnit：它的官方网站是 http://www.junit.org/。您可以从上面获取关于 JUnit 的最新消息。如果您和本文一样在 Eclipse 中使用 JUnit，就不必再下载了。
首先为我们的体验新建一个 Java 工程 —— coolJUnit。现在需要做的是，打开项目 coolJUnit 的属性页 -> 选择“Java Build Path”子选项 -> 点选“Add Library…”按钮 -> 在弹出的“Add Library”对话框中选择 JUnit（图1），并在下一页中选择版本 4.1 后点击“Finish”按钮。这样便把 JUnit 引入到当前项目库中了。

图1 为项目添加 JUnit 库
java单元测试利器JUnit4

请注意 JDK 的版本

JUnit 4.1 是基于 Java 5 的升级版本，它使用了 Tiger 中的很多新特性来简化原有的使用方式。正因为如此，它并不能直接运行在 JDK1.4.x 版本上。如果您需要在 JDK1.4.x 版本使用 JUnit 的话，请使用 3.8.1 版本。

可以开始编写单元测试了吗？等等……，您打算把单元测试代码放在什么地方呢？把它和被测试代码混在一起，这显然会照成混乱，因为单元测试代码是不会出现在最终产品中的。建议您分别为单元测试代码与被测试代码创建单独的目录，并保证测试代码和被测试代码使用相同的包名。这样既保证了代码的分离，同时还保证了查找的方便。遵照这条原则，我们在项目coolJUnit 根目录下添加一个新目录 testsrc，并把它加入到项目源代码目录中（加入方式见图2）。

图2 修改项目源代码目录
java单元测试利器JUnit4

现在我们得到了一条 JUnit 的最佳实践：单元测试代码和被测试代码使用一样的包，不同的目录。

一切准备就绪，一起开始体验如何使用 JUnit 进行单元测试吧。下面的例子来自笔者的开发实践：工具类 WordDealUtil 中的静态方法 wordFormat4DB 是专用于处理 Java 对象名称向数据库表名转换的方法（您可以在代码注释中可以得到更多详细的内容）。下面是第一次编码完成后大致情形：

Java代码<wbr><wbr><a target="_blank" href="http://wing929.iteye.com/blog/219065" title="收藏这段代码" style="text-decoration:none; color:rgb(9,67,130)"><img src="http://wing929.iteye.com/images/icon_star.png" alt="收藏代码" title="java&lt;wbr&gt;单元测试利器JUnit4" style="margin:0px; padding:0px; border:0px; list-style:none"></a></wbr></wbr>

package<wbr>com.ai92.cooljunit;<wbr><wbr></wbr></wbr></wbr>

<wbr><wbr></wbr></wbr>

import<wbr>java.util.regex.Matcher;<wbr><wbr></wbr></wbr></wbr>

import<wbr>java.util.regex.Pattern;<wbr><wbr></wbr></wbr></wbr>

<wbr><wbr></wbr></wbr>

<wbr><wbr></wbr></wbr>

public<wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>class</strong></span><wbr>WordDealUtil<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>public</strong></span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>static</strong></span><wbr>String<wbr>wordFormat4DB(String<wbr>name){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>Pattern<wbr>p<wbr>=<wbr>Pattern.compile(<span style="word-wrap:normal; word-break:normal; color:blue">"[A-Z]"</span>);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>Matcher<wbr>m<wbr>=<wbr>p.matcher(name);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>StringBuffer<wbr>sb<wbr>=<wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>new</strong></span><wbr>StringBuffer();<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>while</strong></span>(m.find()){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>m.appendReplacement(sb,<wbr><span style="word-wrap:normal; word-break:normal; color:blue">"_"</span>+m.group());<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>return</strong></span><wbr>m.appendTail(sb).toString().toLowerCase();<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

}<wbr><wbr></wbr></wbr>

它是否能按照预期的效果执行呢？尝试为它编写JUnit 单元测试代码如下：

Java代码<wbr><wbr><a target="_blank" href="http://wing929.iteye.com/blog/219065" title="收藏这段代码" style="text-decoration:none; color:rgb(9,67,130)"><img src="http://wing929.iteye.com/images/icon_star.png" alt="收藏代码" title="java&lt;wbr&gt;单元测试利器JUnit4" style="margin:0px; padding:0px; border:0px; list-style:none"></a></wbr></wbr>

package<wbr>com.ai92.cooljunit;<wbr><wbr></wbr></wbr></wbr>

<wbr><wbr></wbr></wbr>

import<wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>static</strong></span><wbr>org.junit.Assert.assertEquals;<wbr><wbr></wbr></wbr></wbr></wbr>

import<wbr>org.junit.Test;<wbr><wbr></wbr></wbr></wbr>

<wbr><wbr></wbr></wbr>

public<wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>class</strong></span><wbr>TestWordDealUtil<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(0,130,0); padding:0px; margin:0px; width:auto; border:0px">//测试wordFormat4DB正常运行的情况</span><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(100,100,100)">@Test</span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>public</strong></span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>void</strong></span><wbr>wordFormat4DBNormal(){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>target<wbr>=<wbr><span style="word-wrap:normal; word-break:normal; color:blue">"employeeInfo"</span>;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>result<wbr>=<wbr>WordDealUtil.wordFormat4DB(target);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>assertEquals(<span style="word-wrap:normal; word-break:normal; color:blue">"employee_info"</span>,<wbr>result);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

}<wbr><wbr></wbr></wbr>

很普通的一个类嘛！测试类TestWordDealUtil 之所以使用“Test”开头，完全是为了更好的区分测试类与被测试类。测试方法wordFormat4DBNormal 调用执行被测试方法 WordDealUtil.wordFormat4DB，以判断运行结果是否达到设计预期的效果。需要注意的是，测试方法 wordFormat4DBNormal 需要按照一定的规范书写：

测试方法必须使用注解 org.junit.Test 修饰。
测试方法必须使用 public void 修饰，而且不能带有任何参数。
测试方法中要处理的字符串为“employeeInfo”，按照设计目的，处理后的结果应该为“employee_info”。assertEquals 是由 JUnit 提供的一系列判断测试结果是否正确的静态断言方法（位于类 org.junit.Assert 中）之一，我们使用它将执行结果 result 和预期值“employee_info”进行比较，来判断测试是否成功。

看看运行结果如何。在测试类上点击右键，在弹出菜单中选择 Run As JUnit Test。运行结果如下图所示：

图3 JUnit 运行成功界面
java单元测试利器JUnit4

绿色的进度条提示我们，测试运行通过了。但现在就宣布代码通过了单元测试还为时过早。记住：您的单元测试代码不是用来证明您是对的，而是为了证明您没有错。因此单元测试的范围要全面，比如对边界值、正常值、错误值得测试；对代码可能出现的问题要全面预测，而这也正是需求分析、详细设计环节中要考虑的。显然，我们的测试才刚刚开始，继续补充一些对特殊情况的测试：

Java代码

public<wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>class</strong></span><wbr>TestWordDealUtil<wbr>{<wbr><wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr>……<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(0,130,0); padding:0px; margin:0px; width:auto; border:0px">//测试<wbr>null<wbr>时的处理情况</wbr></wbr></span><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(100,100,100)">@Test</span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>public</strong></span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>void</strong></span><wbr>wordFormat4DBNull(){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>target<wbr>=<wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>null</strong></span>;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>result<wbr>=<wbr>WordDealUtil.wordFormat4DB(target);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>assertNull(result);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(0,130,0); padding:0px; margin:0px; width:auto; border:0px">//测试空字符串的处理情况</span><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(100,100,100)">@Test</span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>public</strong></span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>void</strong></span><wbr>wordFormat4DBEmpty(){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>target<wbr>=<wbr><span style="word-wrap:normal; word-break:normal; color:blue">""</span>;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>result<wbr>=<wbr>WordDealUtil.wordFormat4DB(target);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>assertEquals(<span style="word-wrap:normal; word-break:normal; color:blue">""</span>,<wbr>result);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(0,130,0); padding:0px; margin:0px; width:auto; border:0px">//测试当首字母大写时的情况</span><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(100,100,100)">@Test</span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>public</strong></span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>void</strong></span><wbr>wordFormat4DBegin(){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>target<wbr>=<wbr><span style="word-wrap:normal; word-break:normal; color:blue">"EmployeeInfo"</span>;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>result<wbr>=<wbr>WordDealUtil.wordFormat4DB(target);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>assertEquals(<span style="word-wrap:normal; word-break:normal; color:blue">"employee_info"</span>,<wbr>result);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(0,130,0); padding:0px; margin:0px; width:auto; border:0px">//测试当尾字母为大写时的情况</span><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(100,100,100)">@Test</span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>public</strong></span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>void</strong></span><wbr>wordFormat4DBEnd(){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>target<wbr>=<wbr><span style="word-wrap:normal; word-break:normal; color:blue">"employeeInfoA"</span>;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>result<wbr>=<wbr>WordDealUtil.wordFormat4DB(target);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>assertEquals(<span style="word-wrap:normal; word-break:normal; color:blue">"employee_info_a"</span>,<wbr>result);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(0,130,0); padding:0px; margin:0px; width:auto; border:0px">//测试多个相连字母大写时的情况</span><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(100,100,100)">@Test</span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>public</strong></span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>void</strong></span><wbr>wordFormat4DBTogether(){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>target<wbr>=<wbr><span style="word-wrap:normal; word-break:normal; color:blue">"employeeAInfo"</span>;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>String<wbr>result<wbr>=<wbr>WordDealUtil.wordFormat4DB(target);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>assertEquals(<span style="word-wrap:normal; word-break:normal; color:blue">"employee_a_info"</span>,<wbr>result);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

}<wbr><wbr></wbr></wbr>

<wbr><wbr><wbr>再次运行测试。很遗憾，JUnit 运行界面提示我们有两个测试情况未通过测试（图4）——当首字母大写时得到的处理结果与预期的有偏差，造成测试失败（failure）；而当测试对 null 的处理结果时，则直接抛出了异常——测试错误（error）。显然，被测试代码中并没有对首字母大写和
 null 这两种特殊情况进行处理，修改如下：<wbr></wbr></wbr></wbr></wbr>

Java代码<wbr><wbr><a target="_blank" href="http://wing929.iteye.com/blog/219065" title="收藏这段代码" style="text-decoration:none; color:rgb(9,67,130)"><img src="http://wing929.iteye.com/images/icon_star.png" alt="收藏代码" title="java&lt;wbr&gt;单元测试利器JUnit4" style="margin:0px; padding:0px; border:0px; list-style:none"></a></wbr></wbr>

//修改后的方法wordFormat4DB<wbr><wbr></wbr></wbr>

<wbr><wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>public</strong></span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>static</strong></span><wbr>String<wbr>wordFormat4DB(String<wbr>name){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>if</strong></span>(name<wbr>==<wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>null</strong></span>){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>return</strong></span><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>null</strong></span>;<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>Pattern<wbr>p<wbr>=<wbr>Pattern.compile(<span style="word-wrap:normal; word-break:normal; color:blue">"[A-Z]"</span>);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>Matcher<wbr>m<wbr>=<wbr>p.matcher(name);<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>StringBuffer<wbr>sb<wbr>=<wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>new</strong></span><wbr>StringBuffer();<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>while</strong></span>(m.find()){<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>if</strong></span>(m.start()<wbr>!=<wbr><span style="word-wrap:normal; word-break:normal; color:rgb(192,0,0)">0</span>)<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>m.appendReplacement(sb,<wbr>(<span style="word-wrap:normal; word-break:normal; color:blue">"_"</span>+m.group()).toLowerCase());<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr><wbr><wbr><wbr><wbr><span style="word-wrap:normal; word-break:normal; color:rgb(127,0,85)"><strong>return</strong></span><wbr>m.appendTail(sb).toString().toLowerCase();<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr><wbr>}<wbr><wbr></wbr></wbr></wbr></wbr></wbr></wbr>

图4 JUnit 运行失败界面<wbr></wbr>
<wbr></wbr>

<wbr><wbr><wbr>JUnit 将测试失败的情况分为两种：failure 和 error。Failure 一般由单元测试使用的断言方法判断失败引起，它表示在测试点发现了问题；而 error 则是由代码异常引起，这是测试目的之外的发现，它可能产生于测试代码本身的错误（测试代码也是代码，同样无法保证完全没有缺陷），也可能是被测试代码中的一个隐藏的bug。<wbr></wbr></wbr></wbr></wbr>

请牢记！<wbr></wbr>

<wbr><wbr><wbr>请牢记这一条 JUnit 最佳实践：测试任何可能的错误。单元测试不是用来证明您是对的，而是为了证明您没有错。<wbr></wbr></wbr></wbr></wbr>
<wbr><wbr></wbr></wbr>
<wbr><wbr><wbr>啊哈，再次运行测试，绿条又重现眼前。通过对 WordDealUtil.wordFormat4DB 比较全面的单元测试，现在的代码已经比较稳定，可以作为 API 的一部分提供给其它模块使用了。<wbr></wbr></wbr></wbr></wbr>

<wbr><wbr><wbr>不知不觉中我们已经使用 JUnit 漂亮的完成了一次单元测试。可以体会到 JUnit是多么轻量级，多么简单，根本不需要花心思去研究，这就可以把更多的注意力放在更有意义的事情上——编写完整全面的单元测试</wbr></wbr></wbr>