For example,
test parse.XMLEntityScannerLoad.test("<?xml version="1.0"?><element a1="w" a2="&quot;&quot;"/>"): failure
java.lang.NoClassDefFoundError: com/sun/org/apache/xerces/internal/utils/XMLLimitAnalyzer
at java.xml/com.sun.org.apache.xerces.internal.impl.XMLEntityManager.reset(XMLEntityManager.java:1656)
at java.xml/com.sun.org.apache.xerces.internal.impl.XMLEntityManager.reset(XMLEntityManager.java:1645)
at java.xml/com.sun.org.apache.xerces.internal.parsers.XML11Configuration.resetCommon(XML11Configuration.java:1056)
at java.xml/com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:843)
at java.xml/com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:810)
at java.xml/com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:140)
at java.xml/com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(DOMParser.java:242)
at java.xml/com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(DocumentBuilderImpl.java:339)
at java.xml/javax.xml.parsers.DocumentBuilder.parse(DocumentBuilder.java:122)
at parse.XMLEntityScannerLoad.test(XMLEntityScannerLoad.java:29)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:547)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:85)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:639)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:821)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1131)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:124)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:108)
at org.testng.TestRunner.privateRun(TestRunner.java:773)
at org.testng.TestRunner.run(TestRunner.java:623)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:357)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:352)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:310)
at org.testng.SuiteRunner.run(SuiteRunner.java:259)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1185)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1110)
at org.testng.TestNG.run(TestNG.java:1018)
at com.sun.javatest.regtest.agent.TestNGRunner.main(TestNGRunner.java:89)
at jdk.internal.reflect.GeneratedMethodAccessor14.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:547)
at com.sun.javatest.regtest.agent.MainActionHelper$SameVMRunnable.run(MainActionHelper.java:230)
at java.base/java.lang.Thread.run(Thread.java:844)

and
config Basic.setup(): failure
java.util.ServiceConfigurationError: java.nio.file.spi.FileSystemProvider: Unable to get public provider() method
at java.base/java.util.ServiceLoader.fail(ServiceLoader.java:535)
at java.base/java.util.ServiceLoader.access$200(ServiceLoader.java:345)
at java.base/java.util.ServiceLoader$ProviderImpl.findStaticProviderMethod(ServiceLoader.java:679)
at java.base/java.util.ServiceLoader$ProviderImpl.<init>(ServiceLoader.java:623)
at java.base/java.util.ServiceLoader$ModuleServicesLookupIterator.next(ServiceLoader.java:995)
at java.base/java.util.ServiceLoader$ModuleServicesLookupIterator.next(ServiceLoader.java:901)
at java.base/java.util.ServiceLoader$1.next(ServiceLoader.java:1168)
at java.base/java.util.ServiceLoader$1.next(ServiceLoader.java:1160)
at java.base/java.util.ServiceLoader$2.next(ServiceLoader.java:1268)
at java.base/java.nio.file.spi.FileSystemProvider.loadInstalledProviders(FileSystemProvider.java:119)
at java.base/java.nio.file.spi.FileSystemProvider.access$000(FileSystemProvider.java:77)
at java.base/java.nio.file.spi.FileSystemProvider$1.run(FileSystemProvider.java:169)
at java.base/java.nio.file.spi.FileSystemProvider$1.run(FileSystemProvider.java:166)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.nio.file.spi.FileSystemProvider.installedProviders(FileSystemProvider.java:166)
at java.base/java.nio.file.FileSystems.getFileSystem(FileSystems.java:234)
at Basic.setup(Basic.java:72)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:547)
at org.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:85)
at org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:510)
at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:211)
at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:138)
at org.testng.internal.TestMethodWorker.invokeBeforeClassMethods(TestMethodWorker.java:170)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:104)
at org.testng.TestRunner.privateRun(TestRunner.java:773)
at org.testng.TestRunner.run(TestRunner.java:623)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:357)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:352)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:310)
at org.testng.SuiteRunner.run(SuiteRunner.java:259)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1185)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1110)
at org.testng.TestNG.run(TestNG.java:1018)
at com.sun.javatest.regtest.agent.TestNGRunner.main(TestNGRunner.java:89)
at jdk.internal.reflect.GeneratedMethodAccessor14.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:547)
at com.sun.javatest.regtest.agent.MainActionHelper$SameVMRunnable.run(MainActionHelper.java:230)
at java.base/java.lang.Thread.run(Thread.java:844)
Caused by: java.lang.NoClassDefFoundError: java/nio/file/FileSystemNotFoundException
at java.base/java.lang.Class.getDeclaredMethods0(Native Method)
at java.base/java.lang.Class.privateGetDeclaredMethods(Class.java:3113)
at java.base/java.lang.Class.getMethodsRecursive(Class.java:3254)
at java.base/java.lang.Class.getMethod0(Class.java:3240)
at java.base/java.lang.Class.getMethodOrNull(Class.java:2079)
at java.base/java.lang.System$2.getMethodOrNull(System.java:1992)
at java.base/java.util.ServiceLoader$ProviderImpl.findStaticProviderMethod(ServiceLoader.java:677)
... 41 more
Caused by: java.lang.ClassNotFoundException: java.nio.file.FileSystemNotFoundException
at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:533)
at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:476)
... 48 more


Please note this issue happened only once so far, NoClassDefFoundError happened in a few unrelated tests, other tests run normally.