assertNull(iterator.next(), "Should return null when no next element");
    }

    /**
     * Test multiple iterations with mixed filtering results.
     */
    @Test
    void testMultipleIterationsWithFilter() throws Exception {
        // Given
        when(mockDelegate.hasNext()).thenReturn(true, true, true, false);
        when(mockDelegate.next()).thenReturn(mockFileEntry1, mockFileEntry2, mockFileEntry3);