We are using xUnit 1.29 on all our build machine and they all work fine except on our FreeBSD slave machines.
The exception is as follows (using a simple test xml file... any sample xml can be used... they all fail on our FreeBSD machines):
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[xUnit] [INFO] - Starting to record.
[xUnit] [INFO] - Processing BoostTest-1.x (default)
ERROR: Publisher com.thalesgroup.hudson.plugins.xunit.XUnitPublisher aborted due to exception
hudson.util.IOException2: remote file operation failed: /home/builduser/workspace/xunit tester at hudson.remoting.Channel@7c6159c4:dlpbsd62-32-d1.net
at hudson.FilePath.act(FilePath.java:781)
at hudson.FilePath.act(FilePath.java:767)
at com.thalesgroup.hudson.plugins.xunit.XUnitPublisher.performTests(XUnitPublisher.java:164)
at com.thalesgroup.hudson.plugins.xunit.XUnitPublisher.performXUnit(XUnitPublisher.java:112)
at com.thalesgroup.hudson.plugins.xunit.XUnitPublisher.perform(XUnitPublisher.java:89)
at hudson.tasks.BuildStepMonitor$1.perform(BuildStepMonitor.java:19)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:694)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:669)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:647)
at hudson.model.Build$RunnerImpl.post2(Build.java:162)
at hudson.model.AbstractBuild$AbstractRunner.post(AbstractBuild.java:616)
at hudson.model.Run.run(Run.java:1429)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:230)
Caused by: java.io.IOException: Remote call on dlpbsd62-32-d1.na.rsa.net failed
at hudson.remoting.Channel.call(Channel.java:690)
at hudson.FilePath.act(FilePath.java:774)
... 14 more
Caused by: java.lang.UnsupportedClassVersionError: Bad version number in .class file
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.lang.ClassLoader.defineClass(ClassLoader.java:465)
at hudson.remoting.RemoteClassLoader.loadClassFile(RemoteClassLoader.java:151)
at hudson.remoting.RemoteClassLoader.findClass(RemoteClassLoader.java:142)
at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
at java.lang.ClassLoader.loadClass(ClassLoader.java:251)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:242)
at hudson.remoting.ObjectInputStreamEx.resolveClass(ObjectInputStreamEx.java:48)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1538)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1460)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1693)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1912)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1836)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1713)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1912)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1836)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1713)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:1912)
at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1836)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1713)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1299)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:339)
at hudson.remoting.UserRequest.deserialize(UserRequest.java:178)
at hudson.remoting.UserRequest.perform(UserRequest.java:98)
at hudson.remoting.UserRequest.perform(UserRequest.java:48)
at hudson.remoting.Request$2.run(Request.java:270)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:417)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:269)
at java.util.concurrent.FutureTask.run(FutureTask.java:123)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675)
at java.lang.Thread.run(Thread.java:595)
Finished: FAILURE

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I suspect the problem lies in the Java version on the slave machine, because we were using version 1.10 of xunit and it worked fine.
If any additional information is needed ,please let me know.