### Question:
YubicoClient { public static boolean isValidOTPFormat(String otp) { if (otp == null){ return false; } int len = otp.length(); for (char c : otp.toCharArray()) { if (c < 0x20 || c > 0x7E) { return false; } } return OTP_MIN_LEN <= len && len <= OTP_MAX_LEN; }  abstract VerificationResponse verify(String otp); Integer getClientId(); void setClientId(Integer clientId); void setKey(String key); String getKey(); void setSync(Integer sync); void setMaxRetries(int maxRetries); String[] getWsapiUrls(); void setWsapiUrls(String[] wsapi); void setUserAgent(String userAgent); static YubicoClient getClient(Integer clientId, String key); static String getPublicId(String otp); static boolean isValidOTPFormat(String otp);  }### Answer:
@Test public void testUnPrintableOTP() { String otp = new String(new byte[] {0x01, 0x02, 0x03, 0x04, 0x05, 0x06}); assertFalse(YubicoClient.isValidOTPFormat(otp)); }
@Test public void testShortOTP() { String otp = "cccccc"; assertFalse(YubicoClient.isValidOTPFormat(otp)); }
@Test public void testLongOTP() { String otp = "cccccccccccccccccccccccccccccccccccccccccccccccccc"; assertFalse(YubicoClient.isValidOTPFormat(otp)); }