[taskdef]无法从资源testngtasks加载定义

Selenium Webdriver+testNG+ANT我在运行运行ant runtest时出错C： \硒测试>蚂蚁运行测试构建文件：C:\seleniumtests\build.xml

compileTests：[jar]构建jar:C:\seleniumtests\AntruTests.jar

运行时间：[taskdef]无法从资源testngtasks加载定义。它不能e已找到。

生成失败C： \seleniumtests\build.xml:38:问题：无法创建任务或类型testng原因：名称未定义。操作：检查拼写。操作：检查是否已声明任何自定义任务/类型。措施：检查是否已进行任何/声明。

总时间：1秒

build.xml：

    <?xml version="1.0" encoding="iso-8859-1"?>
<project name="AntruTests">
    <!-- Properties storage -->
    <property file="build.properties"/>
    <!-- Project's folders locations -->
    <property name="project.path" value="." />
    <!-- Set class path libraries to be used for compilation -->
    <path id="class.path">
    <pathelement location="lib" path="lib/selenium-java-2.37.0.jar"/>
    <pathelement location="lib" path="lib/selenium-server-standalone-2.37.0.jar"/>
    </path>

     <!-- Title for ReportNG -->
    <property name="report.title" value="Automated tests report for AntruTests"/>
    <!-- Compile classes -->
    <target name="compileTests"> 
        <javac classpathref="class.path"  includeantruntime="false" destdir="C:seleniumtests" encoding="UTF-8" optimize="off" 
            debug="on" failonerror="true" srcdir="C:seleniumtests" />
            <jar destfile="AntruTests.jar" basedir="C:seleniumtests" />
        </target>
    <target name="prepareForRunning" depends="compileTests">
        <delete dir="${tests.results.folder}" />
        <mkdir dir="${tests.results.folder}" />
</target>

    <target name="runtest" depends="compileTests" description="Runtests">
        <taskdef resource="testngtasks" classpath="${lib.dir}/testng-6.8.7.jar"/>
<testng outputdir="${testng.output.dir}" classpathref="classes">  
<xmlfileset dir="${lib.dir}" includes="testng.xml"/>  
             </testng>
</target>
</project>

我做错了什么？谢谢

<taskdef resource="testngtasks" classpath="${lib.dir}/testng-6.8.7.jar"/>

<taskdef resource="testngtasks" classpath="/usr/local/lib/testng-6.8.7.jar"/>

<taskdef resource="testngtasks" classpath="${test.classpath}"/>