Testing prompts with Github Actions

This guide describes how to automatically run a before vs. after evaluation of edited prompts using the promptfoo Github Action.

On every pull request that modifies a prompt, the action will automatically run a full comparison:

The provided link opens the web viewer interface, which allows you to interactively explore the before vs. after:

Using the Github Action

Here's an example action that watches a PR for modifications. If any file in the prompts/ directory is modified, we automatically run the eval and post a link to the results using the typpo/promptfoo-action@v1:

name: 'Prompt Evaluation'

on:
  pull_request:
    paths:
      - 'prompts/**'

jobs:
  evaluate:
    runs-on: ubuntu-latest
    permissions:
      # This permission is used to post comments on Pull Requests
      pull-requests: write
    steps:
      # This cache is optional, but you'll save money and time by setting it up!
      - name: Set up promptfoo cache
        uses: actions/cache@v2
        with:
          path: ~/.cache/promptfoo
          key: ${{ runner.os }}-promptfoo-v1
          restore-keys: |
            ${{ runner.os }}-promptfoo-

      # This step will actually run the before/after evaluation
      - name: Run promptfoo evaluation
        uses: typpo/promptfoo-action@v1
        with:
          openai-api-key: ${{ secrets.OPENAI_API_KEY }}
          github-token: ${{ secrets.GITHUB_TOKEN }}
          prompts: 'prompts/**/*.json'
          config: 'prompts/promptfooconfig.yaml'
          cache-path: ~/.cache/promptfoo

Configuration

To make this GitHub Action work for your project, you'll need to do a few things:

1. Set paths: Replace 'prompts/**' with the path to the files you want to monitor for changes. This could either be a list of paths to single files, or a directory where your prompts are stored.

   Don't forget to also update the paths in the "Run promptfoo evaluation" step to point to prompts, as well as your promptfooconfig.yaml configuration file.

2. Set OpenAI API key: If you're using an OpenAI API, you need to set the OPENAI_API_KEY secret in your GitHub repository.

   To do this, go to your repository's Settings > Secrets and variables > Actions > New repository secret and create one named OPENAI_API_KEY.

3. Set environment variables: The action uses PROMPTFOO_CONFIG_DIR and PROMPTFOO_CACHE_PATH to record state on the filesystem.

4. Add it to your project: Github automatically runs workflows in the .github/workflows directory, so save it as something like .github/workflows/prompt-eval.yml.

Here are the supported parameters:

Parameter	Description	Required
github-token	The Github token. Used to authenticate requests to the Github API.	Yes
prompts	The glob patterns for the prompt files. These patterns are used to find the prompt files that the action should evaluate.	Yes
config	The path to the configuration file. This file contains settings for the action.	Yes
openai-api-key	The API key for OpenAI. Used to authenticate requests to the OpenAI API.	No
cache-path	The path to the cache. This is where the action stores temporary data.	No

How it works

1. Caching: We use caching to speed up subsequent runs. The cache stores LLM requests and outputs, which can be reused in future runs to save cost.

2. Run Promptfoo Evaluation: This is where the magic happens. We run the evaluation, passing in the configuration file and the prompts we want to evaluate. The results of this step are automatically posted to the pull request.

For more information on how to set up the promptfoo config, see the Getting Started docs.