> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://buildwithfern.com/learn/llms.txt. ## Environment Testing Interface api-reference Created an editable playground environment system for testing API endpoints. Users can now switch between different API environments seamlessly within the documentation. **`openapi.yml`** ```yaml openapi.yml servers: - url: https://api.example.com x-fern-server-name: Production - url: https://sandbox.example.com x-fern-server-name: Sandbox ``` Read the docs