private String generateRandomString(int length) {
    char[] text = new char[length];
    for (int i = 0; i < length; i++) {
      text[i] = ALPHABET.charAt(RANDOM.nextInt(ALPHABET.length()));
    }
    return new String(text);
  }
Generates a string of size {@code length} with random characters from {@link #ALPHABET}.
@param length the length of random string required.
@return a string of size {@code length} with random characters from {@link #ALPHABET}.
ambry-api/src/test/java/com/github/ambry/rest/RestUtilsTest.java