I don't know how to modify the description of the issue. I have refactored my project a bit and some of the provided URL:s are broken. Here is the test that crash on WildFly:

https://github.com/MartinanderssonDotcom/java-ee-concepts/blob/master/src/test/java/com/martinandersson/javaee/jpa/mapping/elementcollection/ElementCollectionDefaultMappingTest.java

And here is the class responsible (does not use @ElementCollection):

https://github.com/MartinanderssonDotcom/java-ee-concepts/blob/master/src/test/java/com/martinandersson/javaee/jpa/mapping/elementcollection/lib/Song.java

However, if one add the @ElementCollection attribute, all is well. Like this class does:

https://github.com/MartinanderssonDotcom/java-ee-concepts/blob/master/src/test/java/com/martinandersson/javaee/jpa/mapping/elementcollection/lib/Person.java

And therefore this test pass:

https://github.com/MartinanderssonDotcom/java-ee-concepts/blob/master/src/test/java/com/martinandersson/javaee/jpa/mapping/elementcollection/ElementCollectionSeparateTableTest.java