### Question:
CertificateUtils { public static String hexify(byte[] bytes) { if (bytes == null) { String errorMsg = "Invalid byte array: 'NULL'"; throw new IllegalArgumentException(errorMsg); } else { char[] hexDigits = new char[]{'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'}; StringBuilder buf = new StringBuilder(bytes.length * 2); for (int i = 0; i < bytes.length; ++i) { buf.append(hexDigits[(bytes[i] & 240) >> 4]); buf.append(hexDigits[bytes[i] & 15]); } return buf.toString(); } }  static String getThumbPrint(Certificate certificate); static String hexify(byte[] bytes); static KeyResolver getKeyResolver();  }### Answer:
@Test public void testHexify() throws Exception { String hexify = CertificateUtils.hexify("randomString".getBytes()); Assert.assertNotNull(hexify); }