How can I test responseCodes using the card holder name?

You can test different resultCodes, by using the desired resultCode as the holderName. For example, to test a PENDING payment use the following request:

{
"amount": {
"currency": "USD",
"value": 1000
},
"reference": "Your order number",
"paymentMethod": {
"type": "scheme",
"number": "4111111111111111",
"expiryMonth": "03",
"expiryYear": "2030",
"holderName": "PENDING",
"cvc": "737"
},
"returnUrl": "https://your-company.com/...",
"merchantAccount": "YOUR_MERCHANT_ACCOUNT"
}

This works the same for all other resultCodes. For more information and details refer to the following page: Testing with card holder name.

Beware that testing a responseCode which includes an underscore using the card holder name which can trigger the non-alphabetical characters risk check, which may cause the payment to be declined with a FRAUD reason code. If this is the case another option to test resultCodes is using the additionalData object which then might be a better solution for your case.