@Test
public void testBytesToHexString() {

    assertEquals(null, StringHelper.bytesToHexString (null));
    assertEquals("", StringHelper.bytesToHexString(new byte[] {}));
    assertEquals("01020304", StringHelper.bytesToHexString(new byte[] {1, 2, 3, 4}));
    assertEquals("0E0F10", StringHelper.bytesToHexString(new byte[] {14, 15, 16}));
    assertEquals("80FF", StringHelper.bytesToHexString(new byte[] {-128, -1}));
}