for (int i = 0; i < 1000; i++) {
            longString.append("x");
        }
        assertEquals(1056L, MemoryUtil.sizeOf(longString.toString()));
    }

    @Test
    public void test_sizeOf_numberTypes() {
        // Test various Number subclasses
        assertEquals(24L, MemoryUtil.sizeOf(new BigInteger("123456789")));
        assertEquals(24L, MemoryUtil.sizeOf(new BigDecimal("123.456")));