我正在尝试在Ubuntu 14.04计算机上运行Diffkit，当我尝试使用以下命令运行测试时，我得到一个空指针异常：
$ java -jar diffkit-app.jar -test
Java的版本是： $ java -version java版＆＃34; 1.7.0_55＆＃34; OpenJDK运行时环境（IcedTea 2.4.7）（7u55-2.4.7-1ubuntu1） OpenJDK 64位服务器VM（内置24.51-b03，混合模式）
我将完整的diffkit解压缩到一个目录中，cd到该目录，运行上面的命令并获得以下输出/堆栈跟踪：
$ java -jar diffkit-app.jar -test
DiffKit home->/home/daveremy/projects/diffkit
dropin dir->/home/daveremy/projects/diffkit/dropin
no jar files in dropin dir
running TestCases
ERROR[11:31:24.460]{main}(DKTestBridge.runTestCases:48)-null
java.lang.NullPointerException: null
at org.codehaus.groovy.runtime.callsite.GetEffectivePojoPropertySite.acceptGetProperty(GetEffectivePojoPropertySite.java:51) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callGetProperty(AbstractCallSite.java:237) [diffkit-app.jar:na]
at org.diffkit.diff.testcase.TestCaseRun.getDiffFailed(TestCaseRun.groovy:92) [diffkit-app.jar:na]
at org.diffkit.diff.testcase.TestCaseRun.this$2$getDiffFailed(TestCaseRun.groovy) [diffkit-app.jar:na]
at org.diffkit.diff.testcase.TestCaseRun$this$2$getDiffFailed.callCurrent(Unknown Source) [na:na]
at org.diffkit.diff.testcase.TestCaseRun.getFailed(TestCaseRun.groovy:83) [diffkit-app.jar:na]
at sun.reflect.GeneratedMethodAccessor82.invoke(Unknown Source) [na:na]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [na:1.7.0_55]
at java.lang.reflect.Method.invoke(Method.java:606) [na:1.7.0_55]
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:88) [diffkit-app.jar:na]
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) [diffkit-app.jar:na]
at groovy.lang.MetaClassImpl$GetBeanMethodMetaProperty.getProperty(MetaClassImpl.java:3462) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.GetEffectivePogoPropertySite.callGroovyObjectGetProperty(GetEffectivePogoPropertySite.java:67) [diffkit-app.jar:na]
at org.diffkit.diff.testcase.TestCaseRun.getReport(TestCaseRun.groovy:121) [diffkit-app.jar:na]
at sun.reflect.GeneratedMethodAccessor81.invoke(Unknown Source) [na:na]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [na:1.7.0_55]
at java.lang.reflect.Method.invoke(Method.java:606) [na:1.7.0_55]
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:88) [diffkit-app.jar:na]
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) [diffkit-app.jar:na]
at groovy.lang.MetaClassImpl$GetBeanMethodMetaProperty.getProperty(MetaClassImpl.java:3462) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.GetEffectivePogoPropertySite.callGetProperty(GetEffectivePogoPropertySite.java:47) [diffkit-app.jar:na]
at org.diffkit.diff.testcase.TestCaseRunner$_generateReport_closure10.doCall(TestCaseRunner.groovy:284) [diffkit-app.jar:na]
at sun.reflect.GeneratedMethodAccessor80.invoke(Unknown Source) [na:na]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [na:1.7.0_55]
at java.lang.reflect.Method.invoke(Method.java:606) [na:1.7.0_55]
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:88) [diffkit-app.jar:na]
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:273) [diffkit-app.jar:na]
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:886) [diffkit-app.jar:na]
at groovy.lang.Closure.call(Closure.java:276) [diffkit-app.jar:na]
at groovy.lang.Closure.call(Closure.java:289) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:1184) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:1160) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.dgm$111.invoke(Unknown Source) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:270) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:52) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:40) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:117) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125) [diffkit-app.jar:na]
at org.diffkit.diff.testcase.TestCaseRunner.generateReport(TestCaseRunner.groovy:284) [diffkit-app.jar:na]
at org.diffkit.diff.testcase.TestCaseRunner.this$2$generateReport(TestCaseRunner.groovy) [diffkit-app.jar:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [na:1.7.0_55]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) [na:1.7.0_55]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [na:1.7.0_55]
at java.lang.reflect.Method.invoke(Method.java:606) [na:1.7.0_55]
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:88) [diffkit-app.jar:na]
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) [diffkit-app.jar:na]
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1058) [diffkit-app.jar:na]
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:886) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.callCurrent(PogoMetaClassSite.java:66) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCallCurrent(CallSiteArray.java:44) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:143) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:151) [diffkit-app.jar:na]
at org.diffkit.diff.testcase.TestCaseRunner$_run_closure2.doCall(TestCaseRunner.groovy:107) [diffkit-app.jar:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [na:1.7.0_55]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) [na:1.7.0_55]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [na:1.7.0_55]
at java.lang.reflect.Method.invoke(Method.java:606) [na:1.7.0_55]
at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:88) [diffkit-app.jar:na]
at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:273) [diffkit-app.jar:na]
at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:886) [diffkit-app.jar:na]
at groovy.lang.Closure.call(Closure.java:276) [diffkit-app.jar:na]
at groovy.lang.Closure.call(Closure.java:289) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:1184) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.DefaultGroovyMethods.each(DefaultGroovyMethods.java:1160) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.dgm$111.invoke(Unknown Source) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoMetaMethodSiteNoUnwrapNoCoerce.invoke(PojoMetaMethodSite.java:270) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:52) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:40) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:117) [diffkit-app.jar:na]
at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:125) [diffkit-app.jar:na]
at org.diffkit.diff.testcase.TestCaseRunner.run(TestCaseRunner.groovy:107) [diffkit-app.jar:na]
at org.diffkit.diff.conf.DKTestBridge.runTestCases(DKTestBridge.java:45) [diffkit-app.jar:na]
at org.diffkit.diff.conf.DKApplication.runTestCases(DKApplication.java:210) [diffkit-app.jar:na]
at org.diffkit.diff.conf.DKApplication.main(DKApplication.java:113) [diffkit-app.jar:na]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [na:1.7.0_55]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) [na:1.7.0_55]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [na:1.7.0_55]
at java.lang.reflect.Method.invoke(Method.java:606) [na:1.7.0_55]
at com.jdotsoft.jarloader.JarClassLoader.invokeMain(JarClassLoader.java:571) [diffkit-app.jar:na]
at org.diffkit.diff.conf.DKLauncher.main(DKLauncher.java:29) [diffkit-app.jar:na]