---
title: AutoViceroyTestBase
summary: Test base class which tests against an ephemeral, generated WASM application.
url: https://www.fastly.com/documentation/reference/compute/sdks/python/fastly_compute/testing/viceroy/class.AutoViceroyTestBase/
---

**Kind:** Class  
**Module:** [viceroy](https://www.fastly.com/documentation/reference/compute/sdks/python/fastly_compute/testing/viceroy/)  
**Package:** fastly-compute 0.1.3  
**Source:** https://github.com/fastly/compute-sdk-python/blob/2bffcc6d596a68bcc0b4342404641deff78e68f6/fastly_compute/testing/viceroy.py#L310

Extends `ViceroyTestBase`.

Test base class which tests against an ephemeral, generated WASM application.

Whereas `ViceroyTestBase` works against an on-disk WASM file, this
lets you put your WASM-side code next to your testrunner code through the
use of the `on_viceroy` decorator, factoring away the build process,
the HTTP requests to Viceroy, and the serialization protocol used in those
requests.

## Methods

### ephemeral_wasm

**Flags:** static  
**Source:** https://github.com/fastly/compute-sdk-python/blob/2bffcc6d596a68bcc0b4342404641deff78e68f6/fastly_compute/testing/viceroy.py#L325

```python
ephemeral_wasm()
```

Build an ad hoc WASM which performs the server-side half of the

The `viceroy_server` fixture then actually runs what we emit.