# Chaotic Response Testing
source: https://developer.mastercard.com/mastercard-gateway/documentation/testing/cha-resp-testing/index.md

The chaotic response allows you to test responses that deviate from the standard test response.

When Chaotic Response is enabled, an element that is not part of the API response is introduced. This allows you to test whether your response-parsing mechanism can handle non-standard responses.

### Features of chaotic response {#features-of-chaotic-response}

* This feature is not intended to identify buffer overflows or test similar security-related aspects. Instead, it is designed to help you parse the response correctly and ignore response items that are not required.

* It applies only to REST-JSON requests and only to test merchants.

* Although it is not currently mandatory, we strongly recommend that you perform this testing to avoid future issues.

* It modifies both standard and error responses.

### Execution of chaotic response header and its usage {#execution-of-chaotic-response-header-and-its-usage}

#### Turning on chaotic responses {#turning-on-chaotic-responses}

Chaotic responses are enabled by including a header in the request. This allows chaotic nodes to be injected into the response body.

Send the chaotic response header when testing that your integration can handle unexpected response data.

**Header name:** `X-MC-Chaotic-Response`

This header allows a REST-JSON request to receive a chaotic response.

**Header value:** Not required and ignored.

The header does not require a value. The header name alone is sufficient to trigger a chaotic response.

**Real-life request:**

The header that is sent is `X-MC-Chaotic-Response`.

**Real-life response:**

The header that is returned is `X-MC-Chaotic-Response-<12 last characters of a UUID>`.

### Chaotic response Postman information {#chaotic-response-postman-information}

For a Postman-based example of chaotic response testing, download the [Postman collection](https://www.postman.com/mastercard/mastercard-developers/collection/4fakvrd/mastercard-gateway-api).