# Testing
source: https://developer.mastercard.com/unified-installments/documentation/testing/index.md

Use this page to plan and execute Sandbox validation for the Mastercard Installments APIs. It covers the recommended workflow, test cases to verify the positive and negative scenarios, and the reference guides you need for endpoint-level execution.  

If the test fails, navigate to the [Codes and Formats](https://developer.mastercard.com/unified-installments/documentation/code-and-formats/index.md) section to identify the applicable error codes, response structure, and recommended actions.
Tip: Start all validation in Sandbox before moving to Production.

## Choose a testing method {#choose-a-testing-method}

Choose a testing method that best matches how you want to validate requests:

* [Postman Collections page](https://developer.mastercard.com/unified-installments/documentation/developer-tools/postman-collection/index.md): pre-built requests with OAuth and encryption configured.
* [Insomnia Collection](https://developer.mastercard.com/unified-installments/documentation/developer-tools/insomnia-collection/index.md): an alternative API client with a ready-to-use workspace.
* [Reference Application](https://developer.mastercard.com/unified-installments/documentation/developer-tools/reference-app/index.md): a working implementation you can run and inspect.
* Custom API client generated as per guidance in [API Basics](https://developer.mastercard.com/unified-installments/documentation/api-basics/index.md#how-to-consume-the-mastercard-installments-api).  

## Recommended testing workflow {#recommended-testing-workflow}

Use this sequence to validate the main endpoint families with a realistic flow:

### Mastercard Installments Credential (MP API) flow {#mastercard-installments-credential-mp-api-flow}

1. Create a merchant with participation details.
2. Retrieve or search for the request ID submitted for merchant.
3. Search merchant participation information.
4. Search specific merchant participation through MID.

### Mastercard Installments Services flow {#mastercard-installments-services-flow}

* Create a list of PANs associated with an installment offer (`POST /consumers/pans/registrations`).
* Retrieve eligible offers for the consumer transaction (`POST /offers`).
* Create the plan that the cardholder selected (`POST /plans`).
* Receive the notification of the selected plan on your endpoint (outbound `POST /notifications`).
1. Fetch eligible offers (`POST /offers`).
2. Create the plan (`POST /plans`).

Open the test scenarios for each API to see how it behaves in different conditions.

|  Mastercard Installments API  |                                                                                                                                                                                                            Testing Details                                                                                                                                                                                                            |
|-------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| Merchant Participation API    | * [Positive test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-program-with-merchant-participation/merchant-participation-api-positivesc/index.md) * [Negative test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-program-with-merchant-participation/merchant-participation-api-negativesc/index.md) |
| Installments Offers API       | * [Positive test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-payment-services/installments-offers-api/index.md#positive-test-scenarios) * [Negative test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-payment-services/installments-offers-api/index.md#negative-test-scenario)                    |
| Installments Plan API         | * [Positive test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-payment-services/installments-plan-api/index.md#positive-test-scenarios) * [Negative test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-payment-services/installments-plan-api/index.md#negative-test-scenario)                        |
| Installments Notification API | * [Positive test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-payment-services/installments-notification-api/index.md#positive-test-scenarios) * [Negative test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-payment-services/installments-notification-api/index.md#negative-test-scenario)        |
| PAN List API                  | * [Positive test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-payment-services/pan-list-api/index.md#positive-test-scenarios) * [Negative test scenario](https://developer.mastercard.com/unified-installments/documentation/testing/mastercard-installments-payment-services/pan-list-api/index.md#negative-test-scenarios)                                         |

## Next steps {#next-steps}

* Consult the [API Reference](https://developer.mastercard.com/unified-installments/documentation/api-reference/mastercard-installments-services/inbound-api/index.md#apis) for complete endpoint specifications, request and response schemas, and environment URLs.
* If you run into issues, visit [Support](https://developer.mastercard.com/unified-installments/documentation/support/index.md) for FAQs and [Codes and Formats](https://developer.mastercard.com/unified-installments/documentation/code-and-formats/index.md) for troubleshooting guidance.