@Test
public void testGetPrimaryKeyAttribute() throws Exception {

    Persistence<Car, Integer> persistence1 = mockPersistence("persistence1");
    Persistence<Car, Integer> persistence2 = mockPersistence("persistence2");
    when(persistence1.getPrimaryKeyAttribute()).thenReturn(Car.CAR_ID);
    when(persistence2.getPrimaryKeyAttribute()).thenReturn(Car.CAR_ID);
    CompositePersistence<Car, Integer> compositePersistence = new CompositePersistence<Car, Integer>(persistence1, persistence2, noAdditionalPersistences());
    assertEquals(Car.CAR_ID, compositePersistence.getPrimaryKeyAttribute());
}