### Question:
WrappingPersistence implements Persistence<O, A> { @Override public SimpleAttribute<O, A> getPrimaryKeyAttribute() { return primaryKeyAttribute; } WrappingPersistence(Collection<O> backingCollection);  WrappingPersistence(Collection<O> backingCollection, SimpleAttribute<O, A> primaryKeyAttribute); @Override boolean supportsIndex(Index<O> index); @Override ObjectStore<O> createObjectStore(); @Override void openRequestScopeResources(QueryOptions queryOptions); @Override void closeRequestScopeResources(QueryOptions queryOptions); @Override SimpleAttribute<O, A> getPrimaryKeyAttribute(); static WrappingPersistence<O, A> aroundCollectionOnPrimaryKey(Collection<O> collection, SimpleAttribute<O, A> primaryKeyAttribute); @SuppressWarnings("unchecked") static WrappingPersistence<O, ? extends Comparable> aroundCollection(Collection<O> collection);  }### Answer:
@Test public void testGetPrimaryKeyAttribute() throws Exception { WrappingPersistence<Car, Integer> wrappingPersistence = WrappingPersistence.aroundCollectionOnPrimaryKey(new HashSet<Car>(), Car.CAR_ID); assertEquals(Car.CAR_ID, wrappingPersistence.getPrimaryKeyAttribute()); }