---
title: viceroy
summary: Testing utilities for Fastly Compute tests.
url: https://www.fastly.com/documentation/reference/compute/sdks/python/fastly_compute/testing/viceroy/
---

**Kind:** Module  
**Package:** fastly-compute 0.1.3  
**Path:** `fastly_compute::testing::viceroy`

Testing utilities for Fastly Compute tests.

This module provides pytest fixtures and base classes for testing
Fastly Compute services with viceroy.

To enable automatic viceroy output on test failures, add this to your conftest.py:

pytest_plugins = ["fastly_compute.pytest_plugin"]

## Classes

| Name | Summary |
| --- | --- |
| [AutoViceroyTestBase](https://www.fastly.com/documentation/reference/compute/sdks/python/fastly_compute/testing/viceroy/class.AutoViceroyTestBase/) | Test base class which tests against an ephemeral, generated WASM application. |
| [ViceroyException](https://www.fastly.com/documentation/reference/compute/sdks/python/fastly_compute/testing/viceroy/class.ViceroyException/) | An exception passed back from Viceroy-dwelling code |
| [ViceroyReturn](https://www.fastly.com/documentation/reference/compute/sdks/python/fastly_compute/testing/viceroy/class.ViceroyReturn/) | A function return value passed back from Viceroy-dwelling code |
| [ViceroyServer](https://www.fastly.com/documentation/reference/compute/sdks/python/fastly_compute/testing/viceroy/class.ViceroyServer/) | Represents a running viceroy server instance. |
| [ViceroyTestBase](https://www.fastly.com/documentation/reference/compute/sdks/python/fastly_compute/testing/viceroy/class.ViceroyTestBase/) | Base class for viceroy tests. |

## Functions

| Name | Summary |
| --- | --- |
| [on_viceroy](https://www.fastly.com/documentation/reference/compute/sdks/python/fastly_compute/testing/viceroy/fn.on_viceroy/) | Decorator for making a method run on the testrunner's Viceroy server |