使用cobertura来测量单元测试的代码覆盖情况

使用 Cobertura 报告代码覆盖率

是否达到 100% 就是问题所在

运行像 Cobertura 或者 Emma 这样的工具时，记住以下方面很重要：在一个特殊的方法中实现 100% 的行覆盖并不意味着该方法没有缺陷或者它已被完全测试。例如，如果您编写了一个针对 if 语句的测试，该测试包含逻辑 And ，而测试针对的是表达式的左侧部分，则像 Cobertura 这样的工具将报告 100% 行覆盖，但是实际上，您仅执行了该语句的 50%；因此仅完成了 50% 的分支覆盖。

现在已经编写了一些测试，如何确定所有这些测试执行什么 呢？幸运的是，此问题可由像 Cobertura 这样的代码覆盖工具来解答。代码覆盖工具可报告测试覆盖率 —— 以行覆盖或分支覆盖形式表示 —— 它表示测试运行时所涉及的代码量。

清单 8 展示了一个 Ant 脚本。该脚本使用 Cobertura 生成一份关于代码覆盖率的 HTML 报告，代码覆盖率通过运行一系列 JUnit 测试获得

Ant的 build.xml文件内容如下：

<?xml version="1.0" encoding="UTF-8"?>

<project name="cobertura.examples.basic" default="coverage" basedir=".">

	<description>
    Cobertura - http://cobertura.sourceforge.net/
    Copyright (C) 2003 jcoverage ltd.
    Copyright (C) 2005 Mark Doliner &lt;[email protected]&gt;
    Copyright (C) 2006 Dan Godfrey
    Cobertura is licensed under the GNU General Public License
    Cobertura comes with ABSOLUTELY NO WARRANTY
    </description>

	<property file="build.properties" />

	<path id="cobertura.classpath">
		<fileset dir="${cobertura.dir}">
			<include name="cobertura.jar" />
			<include name="lib/**/*.jar" />
		</fileset>
	</path>

	<taskdef classpathref="cobertura.classpath" resource="tasks.properties"/>

	<target name="init">
		<mkdir dir="${classes.dir}" />
		<mkdir dir="${instrumented.dir}" />
		<mkdir dir="${reports.xml.dir}" />
		<mkdir dir="${reports.html.dir}" />
		<mkdir dir="${coverage.xml.dir}" />
		<mkdir dir="${coverage.summaryxml.dir}" />
		<mkdir dir="${coverage.html.dir}" />
	</target>

	<target name="compile" depends="init">
		<javac srcdir="${src.dir}" destdir="${classes.dir}" debug="yes">
			<classpath refid="cobertura.classpath" />
		</javac>
	</target>

	<target name="instrument" depends="init,compile">
		<!--
			Remove the coverage data file and any old instrumentation.
		-->
		<delete file="cobertura.ser"/>
		<delete dir="${instrumented.dir}" />

		<!--
			Instrument the application classes, writing the
			instrumented classes into ${build.instrumented.dir}.
		-->
		<cobertura-instrument todir="${instrumented.dir}">
			<!--
				The following line causes instrument to ignore any
				source line containing a reference to log4j, for the
				purposes of coverage reporting.
			-->
			<ignore regex="org.apache.log4j.*" />

			<fileset dir="${classes.dir}">
				<!--
					Instrument all the application classes, but
					don't instrument the test classes.
				-->
				<include name="**/*.class" />
				<exclude name="**/*Test.class" />
			</fileset>
		</cobertura-instrument>
	</target>

	<target name="test" depends="init,compile">
		<junit fork="yes" dir="${basedir}" failureProperty="test.failed">
			<!--
				Note the classpath order: instrumented classes are before the
				original (uninstrumented) classes.  This is important.
			-->
			<classpath location="${instrumented.dir}" />
			<classpath location="${classes.dir}" />

			<!--
				The instrumented classes reference classes used by the
				Cobertura runtime, so Cobertura and its dependencies
				must be on your classpath.
			-->
			<classpath refid="cobertura.classpath" />

			<formatter type="xml" />
			<test name="${testcase}" todir="${reports.xml.dir}" if="testcase" />
			<batchtest todir="${reports.xml.dir}" unless="testcase">
				<fileset dir="${src.dir}">
					<include name="**/*Test.java" />
				</fileset>
			</batchtest>
		</junit>

		<junitreport todir="${reports.xml.dir}">
			<fileset dir="${reports.xml.dir}">
				<include name="TEST-*.xml" />
			</fileset>
			<report format="frames" todir="${reports.html.dir}" />
		</junitreport>
	</target>

	<target name="coverage-check">
		<cobertura-check branchrate="34" totallinerate="100" />
	</target>

	<target name="coverage-report">
		<!--
			Generate an XML file containing the coverage data using
			the "srcdir" attribute.
		-->
		<cobertura-report srcdir="${src.dir}" destdir="${coverage.xml.dir}" format="xml" />
	</target>

	<target name="summary-coverage-report">
		<!--
			Generate an summary XML file containing the coverage data using
			the "srcdir" attribute.
		-->
		<cobertura-report srcdir="${src.dir}" destdir="${coverage.summaryxml.dir}" format="summaryXml" />
	</target>

	<target name="alternate-coverage-report">
		<!--
			Generate a series of HTML files containing the coverage
			data in a user-readable form using nested source filesets.
		-->
		<cobertura-report destdir="${coverage.html.dir}">
			<fileset dir="${src.dir}">
				<include name="**/*.java"/>
			</fileset>
		</cobertura-report>
	</target>

	<target name="clean" description="Remove all files created by the build/test process.">
		<delete dir="${classes.dir}" />
		<delete dir="${instrumented.dir}" />
		<delete dir="${reports.dir}" />
		<delete file="cobertura.log" />
		<delete file="cobertura.ser" />
	</target>

	<target name="coverage" depends="compile,instrument,test,coverage-report,summary-coverage-report,
alternate-coverage-report" description="Compile,
 instrument ourself, run the tests and generate JUnit and coverage reports."/>

</project>

Ant的 build.properties文件内容如下：

# The source code for the examples can be found in this directory
src.dir=src

# The path to cobertura.jar
cobertura.dir=../..

# Classes generated by the javac compiler are deposited in this directory
classes.dir=classes

# Instrumented classes are deposited into this directory
instrumented.dir=instrumented

# All reports go into this directory
reports.dir=reports

# Unit test reports from JUnit are deposited into this directory
reports.xml.dir=${reports.dir}/junit-xml
reports.html.dir=${reports.dir}/junit-html

# Coverage reports are deposited into these directories
coverage.xml.dir=${reports.dir}/cobertura-xml
coverage.summaryxml.dir=${reports.dir}/cobertura-summary-xml
coverage.html.dir=${reports.dir}/cobertura-html

 

  Cobertura 产生了一个如图 1 中所示的 HTML 报告。请注意行覆盖和分支覆盖的百分比是以包计算的。可单击每一个包，获得类级别的行百分比和路径百分比，甚至能看到执行的源代码行和它们执行的次数。