# Integration and Testing
source: https://developer.mastercard.com/merchant-identifier/documentation/integration-and-testing/index.md

## Ready to begin Testing? {#ready-to-begin-testing}

Tip: We recommend that you begin testing in the sandbox.

Once you have created a project on Mastercard Developers and generated sandbox credentials you can start testing.   

* The base URL for calling Sandbox endpoints is: <https://sandbox.api.mastercard.com/merchant-identifier>.   
* The base URL for calling Production endpoints is: <https://api.mastercard.com/merchant-identifier>.  
* You can test the Sandbox/Production:   

1. Using our [Reference Application](https://developer.mastercard.com/merchant-identifier/documentation/reference-app/index.md),   
2. Or using [Insomnia](https://insomnia.rest/),   
3. Or using [Postman Collections](https://developer.mastercard.com/merchant-identifier/documentation/postman-collection/index.md) (recommended approach).

## Insomnia {#insomnia}

> * Insomnia is an open-source API client developers use to quickly and easily send REST requests to Mastercard APIs. Mastercard developed an [Insomnia plugin](https://github.com/Mastercard/insomnia-plugin-mastercard) for handling API authentication.
> * This [Insomnia Tutorial](https://developer.mastercard.com/platform/tutorial/use-insomnia-rest-client-for-mastercard-apis/) explains how to test the Places API using the Insomnia Rest API client.

## Postman {#postman}

> * Postman Collections allows developers to test your API's calls in sandbox and production environments without writing any code. This makes sharing pre-formed API requests with partners extremely easy, and permits partners to run individual API requests or those within a folder or the entire collection.
> * To start, go to our [Postman Collections page](https://developer.mastercard.com/merchant-identifier/documentation/postman-collection/index.md).
> * For detailed steps, follow our [Postman tutorial](https://developer.mastercard.com/platform/tutorial/use-postman-for-mastercard-apis/).

## Sandbox Test Data {#sandbox-test-data}

For list of sandbox data containing merchant descriptors and card acceptors please click [here](https://static.developer.mastercard.com/content/merchant-identifier/uploads/merchant-identifier-sandbox-merchant-descriptors.xlsx)