While trying to generate a mockup for
oracle.wsm.policy.model.impl.SimpleAssertion

SimpleAssertion simpleAsserter = new MockUp() {

}.getMockInstance();

if fails with jmockup since version 1.10+.
In previous versions it works.

java.lang.NullPointerException
at java.util.HashMap.(HashMap.java:223)
at oracle.wsm.policy.model.impl.SimpleAssertion.hashCode(SimpleAssertion.java:777)
at java.util.HashMap.getEntry(HashMap.java:344)
at java.util.HashMap.containsKey(HashMap.java:335)
at java.util.HashSet.contains(HashSet.java:184)
at java.util.AbstractCollection.retainAll(AbstractCollection.java:369)
at mockit.internal.state.MockClasses$SavePoint.rollback(MockClasses.java:165)
at mockit.internal.state.SavePoint.rollback(SavePoint.java:42)
at mockit.integration.internal.TestRunnerDecorator.discardTestLevelMockedTypes(TestRunnerDecorator.java:123)
at mockit.integration.internal.TestRunnerDecorator.cleanUpMocks(TestRunnerDecorator.java:85)
at mockit.integration.internal.TestRunnerDecorator.cleanUpMocksFromPreviousTestClass(TestRunnerDecorator.java:80)
at mockit.integration.junit4.internal.RunNotifierDecorator.fireTestRunFinished(RunNotifierDecorator.java:28)
at org.junit.runner.notification.RunNotifier.fireTestRunFinished(RunNotifier.java)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:51)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)