javax.persistence.PersistenceException: org.hibernate.PropertyValueException: not-null property references a null or transient value : org.hibernate.jpa.test.mapping.UnidirectionalOneToManyUniqueConstraintOrderColumnTest$ChildData._children_parentIdBackref
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:154)
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:181)
	at org.hibernate.internal.ExceptionConverterImpl.convert(ExceptionConverterImpl.java:188)
	at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:811)
	at org.hibernate.internal.SessionImpl.persist(SessionImpl.java:789)
	at org.hibernate.jpa.test.mapping.UnidirectionalOneToManyUniqueConstraintOrderColumnTest.lambda$testRemovingOneAndAddingTwoElements$4(UnidirectionalOneToManyUniqueConstraintOrderColumnTest.java:116)
	at org.hibernate.testing.transaction.TransactionUtil.doInJPA(TransactionUtil.java:210)
	at org.hibernate.testing.transaction.TransactionUtil.doInJPA(TransactionUtil.java:251)
	at org.hibernate.jpa.test.mapping.UnidirectionalOneToManyUniqueConstraintOrderColumnTest.testRemovingOneAndAddingTwoElements(UnidirectionalOneToManyUniqueConstraintOrderColumnTest.java:108)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.hibernate.testing.junit4.ExtendedFrameworkMethod.invokeExplosively(ExtendedFrameworkMethod.java:45)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:298)
	at org.junit.internal.runners.statements.FailOnTimeout$CallableStatement.call(FailOnTimeout.java:292)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.lang.Thread.run(Thread.java:748)
Caused by: org.hibernate.PropertyValueException: not-null property references a null or transient value : org.hibernate.jpa.test.mapping.UnidirectionalOneToManyUniqueConstraintOrderColumnTest$ChildData._children_parentIdBackref
	at org.hibernate.engine.internal.Nullability.checkNullability(Nullability.java:111)
	at org.hibernate.engine.internal.Nullability.checkNullability(Nullability.java:55)
	at org.hibernate.action.internal.AbstractEntityInsertAction.nullifyTransientReferencesIfNotAlready(AbstractEntityInsertAction.java:115)
	at org.hibernate.action.internal.AbstractEntityInsertAction.makeEntityManaged(AbstractEntityInsertAction.java:124)
	at org.hibernate.engine.spi.ActionQueue.addResolvedEntityInsertAction(ActionQueue.java:289)
	at org.hibernate.engine.spi.ActionQueue.addInsertAction(ActionQueue.java:263)
	at org.hibernate.engine.spi.ActionQueue.addAction(ActionQueue.java:250)
	at org.hibernate.event.internal.AbstractSaveEventListener.addInsertAction(AbstractSaveEventListener.java:340)
	at org.hibernate.event.internal.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:289)
	at org.hibernate.event.internal.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:196)
	at org.hibernate.event.internal.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:139)
	at org.hibernate.event.internal.DefaultPersistEventListener.entityIsTransient(DefaultPersistEventListener.java:192)
	at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:135)
	at org.hibernate.event.internal.DefaultPersistEventListener.onPersist(DefaultPersistEventListener.java:62)
	at org.hibernate.internal.SessionImpl.firePersist(SessionImpl.java:804)
	... 20 more