# Integration and Testing
source: https://developer.mastercard.com/straight-through-processing/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, generated sandbox credentials and received approvals, you can start testing.

## Straight Through Processing Test Cases Tutorial {#straight-through-processing-test-cases-tutorial}

Follow our [Tutorials and Guides](https://developer.mastercard.com/straight-through-processing/documentation/tutorials-and-guides/index.md) for help about Payment Acceptance service specific test cases.

### Base URLs for Testing: {#base-urls-for-testing}

* Sandbox
* Production

```Sandbox
https://sandbox.api.mastercard.com/stp-api/v1 
```

```Production
https://api.mastercard.com/stp-api/v1
```

## Methods of testing Sandbox/Production: {#methods-of-testing-sandboxproduction-br}

### 1. Reference Application {#1-reference-application}

> * Our Spring Boot Reference Application acts as an API client and allows you to integrate different operations.
> * For detailed steps, follow our [Reference Application](https://developer.mastercard.com/straight-through-processing/documentation/reference-app/index.md).

### 2. Insomnia {#2-insomnia}

> * [Insomnia](https://insomnia.rest/) is an open-source API client that developers use to quickly and easily send REST requests to Mastercard APIs. API Consultancy \& Standards developed an [Insomnia Plugin](https://github.com/Mastercard/insomnia-plugin-mastercard) for handling API authentication.
> * Follow our [Insomnia Tutorial](https://developer.mastercard.com/straight-through-processing/tutorial/integration-and-testing/index.md) to learn how to test the STP OAuth API using Insomnia.

## Next Steps {#next-steps}

* You can head to our [Reference Application](https://developer.mastercard.com/straight-through-processing/documentation/reference-app/index.md) page to download our Spring Boot Application that shows a typical usage of the Payment Acceptance API.
* To learn more about any error codes you receive, head over to our [Codes and Formats](https://developer.mastercard.com/straight-through-processing/documentation/code-and-formats/hypermedia/index.md) section to learn about the details of all the error codes.