@Test
public void testGetBytesUsed() {

    DiskPersistence<Car, Integer> persistence = DiskPersistence.onPrimaryKey(Car.CAR_ID);
    @SuppressWarnings("MismatchedQueryAndUpdateOfCollection")
    IndexedCollection<Car> cars = new ConcurrentIndexedCollection<Car>(persistence);
    cars.addAll(CarFactory.createCollectionOfCars(50));
    long bytesUsed = persistence.getBytesUsed();
    Assert.assertTrue("Bytes used should be greater than zero: " + bytesUsed, bytesUsed > 0);
    Assert.assertTrue("Failed to delete temp file:" + persistence.getFile(), persistence.getFile().delete());
}