# Testing overview

## How to test your code that uses the SDK

The published SDK artifact doesn't include a fake, in-memory, or stub implementation of `RatepayClient`
for you to import into your tests. What it does provide is a **plain interface** designed for exactly this
purpose: you can mock it, fake it, or wrap it.

In practice, that means the standard approach, mocking `RatepayClient` with whatever mocking library your
project already uses, works cleanly: it's a normal public interface with no final classes or sealed
restrictions blocking it. See [Unit testing the quickstart flow](/docs/developer/sdk/testing/unit-testing-the-quickstart-flow)
for a worked example.

## Sandbox vs. mocked tests

Mocking `RatepayClient` is for testing *your own code's logic* against the SDK's contract, branching on
outcomes, mapping exceptions, retry logic etc, without making network calls. It doesn't validate that your
actual request payloads are accepted by the real API. For that, run the same flow against
`Environment.INTEGRATION` - see [Sandbox testing](/docs/developer/sdk/testing/sandbox-testing).