On java 11 you get an error in your junit test when the code in PowerMockAgent is used because of this:

`public final class PowerMockAgent
{

static final String javaSpecVersion = System.getProperty("java.specification.version");
static final boolean jdk6OrLater = "1.6".equals(javaSpecVersion) || "1.7".equals(javaSpecVersion) || "1.8".equals(javaSpecVersion)
    || "9".equals(javaSpecVersion);

`

So computing the information about the version after jdk6 or before it does not take into account that for java 11 the javaSpecVersion variable is "11".
Consequently you get the following error:

java.lang.RuntimeException: java.lang.IllegalStateException: PowerMock requires a Java 5 VM or later.
at org.powermock.modules.agent.PowerMockClassRedefiner.redefine(PowerMockClassRedefiner.java:40)
at org.powermock.modules.agent.support.PowerMockAgentTestInitializer.redefine(PowerMockAgentTestInitializer.java:62)
at org.powermock.modules.agent.support.PowerMockAgentTestInitializer.redefineClassesToPrepare(PowerMockAgentTestInitializer.java:57)
at org.powermock.modules.agent.support.PowerMockAgentTestInitializer.redefineClasses(PowerMockAgentTestInitializer.java:44)
at org.powermock.modules.agent.support.PowerMockAgentTestInitializer.initialize(PowerMockAgentTestInitializer.java:34)
at org.powermock.modules.junit4.rule.PowerMockRule.apply(PowerMockRule.java:47)
at org.junit.runners.BlockJUnit4ClassRunner.withMethodRules(BlockJUnit4ClassRunner.java:365)
at org.junit.runners.BlockJUnit4ClassRunner.withRules(BlockJUnit4ClassRunner.java:355)
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:566)
at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:246)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.withRulesReflectively(SpringJUnit4ClassRunner.java:313)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:303)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:246)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:97)
at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:190)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)
Caused by: java.lang.IllegalStateException: PowerMock requires a Java 5 VM or later.
at org.powermock.modules.agent.AgentInitialization.initializeAccordingToJDKVersion(AgentInitialization.java:48)
at org.powermock.modules.agent.PowerMockAgent.verifyInitialization(PowerMockAgent.java:84)
at org.powermock.modules.agent.PowerMockAgent.instrumentation(PowerMockAgent.java:77)
at org.powermock.modules.agent.PowerMockClassRedefiner.redefine(PowerMockClassRedefiner.java:38)
... 31 more