testng xml中按顺序执行java类

如红字部份，将安顺序执行4个类

<?xml version="1.0" encoding="UTF-8"?>
<suite name="BugFree测试" thread-count="2" parallel="tests">
 <listeners>
    <listener class-name="org.uncommons.reportng.HTMLReporter" />
     <listener class-name="org.uncommons.reportng.JUnitXMLReporter" />
  </listeners>
 
      <test name="BugFreeTest" preserver-order="true">
        <classes preserver-order="true">
          <class name="testcase.LoginPass"/>
           <class name="testcase.LoginFail"/>
            <class name="testcase.AddBug"/>
            <class name="testcase.EditBug"/>
        </classes>
        
       </test> <!-- Test -->
  </suite> <!-- Suite -->