# Testing with Insomnia for IES
source: https://developer.mastercard.com/account-to-account-commerce-for-csp/tutorial/insomnia-ies/index.md

### Overview {#overview}

Participants are often expected to validate the complete agreement lifecycle or payment journey when supporting Mastercard® Account‑to‑Account Commerce. This requires true end‑to‑end testing, where each interaction behaves exactly as it would in a real-world ecosystem.  

This guide empowers Participants to step into the shoes of the opposite entity, allowing them to accurately simulate counterpart behavior and drive their test cases to successful completion. By doing so, teams can confidently validate integrations without waiting on external dependencies.  

The Insomnia for IES pack serves as a practical companion throughout this process, offering a clear view of sample request and response payloads and helping Participants understand how each API interaction should look and behave.  

From downloading Insomnia to executing calls and validating outcomes, this guide walks through the journey step by step, ensuring Participants can set up their environment, run tests seamlessly, and verify results with confidence.  

### Prerequisites {#prerequisites}

Mastercard provides CSPs with Insomnia test packs containing scripts to simulate responses received from a DSP. Before testing A2AC APIs with Insomnia, ensure the following prerequisites are met:

* Create a project for the Mastercard A2AC API. Refer to the 'Creating a Sandbox Project' section for details.
* Download and install the [Insomnia tool](https://insomnia.rest/).
* Install the Mastercard Insomnia Plugin.
* CSP must download the Insomnia test pack which contains test cases and other supporting files in [CSP PACK for IEXS](https://static.developer.mastercard.com/content/account-to-account-commerce-for-csp/uploads/CSP_PACK_FOR_IEXS.zip)
[](https://static.developer.mastercard.com/content/account-to-account-commerce-for-csp/uploads/CSP_PACK_FOR_IEXS.zip)
* [Review the test cases](https://static.developer.mastercard.com/content/account-to-account-commerce-for-csp/uploads/CSP_PACK_FOR_IEXS.zip)[IES CSP Test Cases V1.0](/uploads/IES CSP Test Cases V1.0.xlsx).   

Following are the files which are available in the zip. Participants are just required to use them as described in the tutorial:

|                     Item                     |                Type                |
|----------------------------------------------|------------------------------------|
| A2A-MTF-TEST-CLIENT.pfx                      | Client certificate                 |
| decryption-private-keymtf.key                | MTF key file                       |
| CSP_Customer-Accrediation-Pack-for-IEXS.yaml | yaml file                          |
| encryptioncertmtf.pem                        | Security Certificate               |
| signcertificate.key                          | Signature certificate              |
| signverificationcertificate.pem              | Signature Verification Certificate |

![iesfolder](https://static.developer.mastercard.com/content/account-to-account-commerce-for-csp/uploads/insomniaslides/iexspack1.png)

### Self-Test Environment Overview {#self-test-environment-overview}

The test pack covers the following use cases:   

#### Receive Alias Resolution Request {#receive-alias-resolution-request}

* Request Alias Resolution for Alias Type "EMAL"
* Request Alias Resolution for Alias Type "PHON"

#### Send Alias Resolution Update for below scenarios {#send-alias-resolution-update-for-below-scenarios}

* Alias Resolution Successful
  * Resolve Bank Account Details Associated with Alias
  * Resolve Wallet Account Details Associated with Alias
* Alias Resolution Rejected (MULT)
* Alias Resolution Rejected (NTFD)
* Alias Resolution Rejected (ACCD)
* Alias Resolution Rejected (LCNF)
* Alias Resolution Rejected (OTHR)