How to use `MockServices` for Unit Tests in Corda 4?

In Corda Enterprise 4.2, I’m trying to wrap up an Unit Test using some custom made JPA tables, and I’m having problem with the following code:

serviceHub = MockServices(CordaX500Name.parse("O=OOO,L=Lambari,C=BR"))
serviceHub.withEntityManager{
    val entityManager = this
    test = CustomJPABackedClass() 
    entityManager.persist(test)
}

This code produces the following exception:

java.lang.UnsupportedOperationException
    at net.corda.testing.node.MockServices.withEntityManager(MockServices.kt:412)
    at project.support.CustomSupportTest$Companion.setupTest(CustomSupportTest.kt:70)
    at project.support.CustomSupportTest.setupTest(CustomSupportTest.kt)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:24)
    at org.hibernate.testing.junit4.BeforeClassCallbackHandler.evaluate(BeforeClassCallbackHandler.java:26)
    at org.hibernate.testing.junit4.AfterClassCallbackHandler.evaluate(AfterClassCallbackHandler.java:25)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

How to properly use this MockServices(or something else) to produce quick Unit tests ?