public void testFailWithUnknownOperation() {
   try {
     CaptchaParser.generateHumanReadableCaptcha("02100003");
     fail("Function should have thrown a WrongCaptchaOperationException.");
   } catch (WrongCaptchaLengthException e) {
     fail("Function should have thrown a WrongCaptchaOperationException.");
   } catch (WrongCaptchaOperationException e) {
     // ok
   }
 }
 public void testFailForWrongLength() {
   try {
     CaptchaParser.generateHumanReadableCaptcha("1");
     fail("Function should have thrown a WrongCaptchaLengthException.");
   } catch (WrongCaptchaLengthException e) {
     // ok
   } catch (WrongCaptchaOperationException e) {
     fail("Function should have thrown a WrongCaptchaLengthException.");
   }
 }
  public void testGenerateCaptchaWithMultiply() {
    String firstNumber = "01";
    String secondNumber = "02";
    String goodCaptchaWithSum = firstNumber + CaptchaParser.MULT + secondNumber;

    try {
      String result = CaptchaParser.generateHumanReadableCaptcha(goodCaptchaWithSum);
      assertEquals(firstNumber + " * " + secondNumber + FIXED_CAPTCHA_TAIL, result);
    } catch (WrongCaptchaLengthException e) {
      Log.e(TAG, e.getMessage(), e);
      fail("Function should have not thrown a WrongCaptchaLengthException.");
    } catch (WrongCaptchaOperationException e) {
      Log.e(TAG, e.getMessage(), e);
      fail("Function should have not thrown a WrongCaptchaOperationException.");
    }
  }