Hibernate is not able to resolve Entity Mappings for Association Attributes. I took a simple self join example and tried to build the sessionFactory using hbm.xml file. The same code works fine on Hibernate 4.3 but throws the following exception in Hibernate 5.2 :

_java.lang.IllegalArgumentException: Expecting collection type [org.hibernate.type.BagType]
at org.hibernate.metamodel.internal.AttributeFactory.determineCollectionType(AttributeFactory.java:930)
at org.hibernate.metamodel.internal.AttributeFactory$PluralAttributeMetadataImpl.<init>(AttributeFactory.java:779)
at org.hibernate.metamodel.internal.AttributeFactory$PluralAttributeMetadataImpl.<init>(AttributeFactory.java:760)
at org.hibernate.metamodel.internal.AttributeFactory.determineAttributeMetadata(AttributeFactory.java:541)
at org.hibernate.metamodel.internal.AttributeFactory.buildAttribute(AttributeFactory.java:77)
at org.hibernate.metamodel.internal.MetadataContext.wrapUp(MetadataContext.java:213)
at org.hibernate.metamodel.internal.MetamodelImpl.initialize(MetamodelImpl.java:220)
at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:295)
at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:490)
at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:710)
at org.hibernate.testing.junit4.BaseCoreFunctionalTestCase.buildSessionFactory(BaseCoreFunctionalTestCase.java:107)
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.hibernate.testing.junit4.TestClassMetadata.performCallbackInvocation(TestClassMetadata.java:200)
at org.hibernate.testing.junit4.TestClassMetadata.invokeCallback(TestClassMetadata.java:187)
at org.hibernate.testing.junit4.TestClassMetadata.performCallbacks(TestClassMetadata.java:181)
at org.hibernate.testing.junit4.TestClassMetadata.performBeforeClassCallbacks(TestClassMetadata.java:172)
at org.hibernate.testing.junit4.BeforeClassCallbackHandler.evaluate(BeforeClassCallbackHandler.java:25)
at org.hibernate.testing.junit4.AfterClassCallbackHandler.evaluate(AfterClassCallbackHandler.java:25)
at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:264)
at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:153)
at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:124)
at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:200)
at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)_

The discussion related to the problem is @ https://forum.hibernate.org/viewtopic.php?f=1&t=1044389
As per the team request, i have also added the test-case using JPA test-case template @
https://github.com/hibernate/hibernate-test-case-templates/pull/19

Let me know if you need any other details.