> For the complete documentation index, see [llms.txt](https://docs.idlayr.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.idlayr.com/products/eligibility/testing.md).

# Testing in sandbox

{% hint style="info" %}
**Backend API** · GA
{% endhint %}

Test Eligibility without real MNO traffic by using a sandbox project. The last digits of the `phone_number` (or specific test IPs) drive the simulated outcome.

See [Project modes](/get-started/concepts/project-modes.md) for the general sandbox model.

## How sandbox testing works

In sandbox mode, IDlayr returns simulated eligibility responses based on the MSISDN suffix or test IP. The shape of the response is the same as production.

## By Mobile IP Address — IP suffix map

| IP ends with           | HTTP status | Meaning                 |
| ---------------------- | ----------- | ----------------------- |
| Even last digit        | 200         | Success, eligible       |
| Odd last digit         | 412         | Not a mobile IP address |
| `99` (last two digits) | 400         | MNO not supported       |

## By Phone Number — MSISDN suffix map

Phone-number sandbox values follow the conventional MSISDN-suffix pattern used across IDlayr products (even/odd last digit drives match/no-match; `00`, `55`, `99` drive error states). The specific outcome values for the v1 phone-number endpoint will be confirmed at onboarding.

For the cross-product overview of sandbox — what's simulated, what isn't, sandbox retention — see [Sandbox testing](/get-started/sandbox-testing.md).

## What sandbox doesn't simulate

* Real production carrier coverage shifts.
* Live MNO query latency variance.

Run a small set of production checks against real numbers in your target markets before going live.


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