The junit xml file was generate by a python script. The format is:
<testsuites><testsuite name="testsuit name"><testcase name="test case name" result="PASS" /></testsuite></testsuites>

The version of JUnit Plugin is: 1.11

Recording test results
ERROR: Publisher hudson.tasks.junit.JUnitResultArchiver aborted due to exception
java.lang.NoClassDefFoundError: hudson/tasks/junit/JUnitParser$ParseResultCallable
at hudson.tasks.junit.JUnitParser.parseResult(JUnitParser.java:103)
at hudson.tasks.junit.JUnitResultArchiver.parse(JUnitResultArchiver.java:126)
at hudson.tasks.junit.JUnitResultArchiver.perform(JUnitResultArchiver.java:144)
at hudson.tasks.BuildStepCompatibilityLayer.perform(BuildStepCompatibilityLayer.java:74)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:20)
at hudson.model.AbstractBuild$AbstractBuildExecution.perform(AbstractBuild.java:770)
at hudson.model.AbstractBuild$AbstractBuildExecution.performAllBuildSteps(AbstractBuild.java:734)
at hudson.model.Build$BuildExecution.post2(Build.java:183)
at hudson.model.AbstractBuild$AbstractBuildExecution.post(AbstractBuild.java:683)
at hudson.model.Run.execute(Run.java:1770)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:43)
at hudson.model.ResourceController.execute(ResourceController.java:89)
at hudson.model.Executor.run(Executor.java:240)