Testing Expert
Use this agent for Output.ai testing strategies including Vitest configuration, Temporal workflow testing, LLM mocking, integration testing, and test performance optimization. Specializes in JavaScript testing patterns with Output.ai abstractions.
- Type
- Subagent
- Repository
- growthxai/output
- GitHub stars
- 439
- License
- Apache-2.0
- Repo last updated
- Sep 25, 2026
- Source file
- .claude/agents/testing-expert.md
What Testing Expert is
Testing Expert is a subagent published in the growthxai/output repository on GitHub, which has about 439 stars. The repository describes itself as: “The open-source TypeScript framework for building AI workflows and agents. Designed for Claude Code describe what you want, Claude builds it, with all the best practices already in place.”
A subagent is a specialist assistant that Claude can hand part of a task to. It is a markdown file whose frontmatter sets a name, a description that tells Claude when to delegate, and optionally the tools and model it may use; the body becomes the subagent's own system prompt.
Because a subagent works in its own context, it keeps the main conversation focused: Claude can send a narrow job, such as a review or a specialised analysis, to Testing Expert and get back a compact result.
How to install Testing Expert
Claude Code
- Download testing-expert.md from the repository.
- Save it to ~/.claude/agents/ to use it in every project, or to .claude/agents/ inside one project to share it through version control.
- Claude Code watches these folders, so the subagent is usually available right away. Ask Claude to use it by name, or @-mention it to make sure it runs.
Claude Cowork
- Cowork loads subagents through plugins. If the repository is packaged as a plugin marketplace, add it under Customize → Plugins → Add marketplace and install the plugin that contains this subagent.
- Otherwise, bundle the file into your own plugin's agents/ folder and upload it from Customize → Plugins.
New to extending Cowork? Our plugins guide and Customize guide explain how skills, plugins, and connectors fit together.
Inside the source file
An excerpt from .claude/agents/testing-expert.md, shared under the repository's Apache-2.0 license. Read the full file on GitHub.
Role Definition
You are an expert in testing for the Output.ai project, with deep knowledge of:
- Vitest configuration and testing patterns
- Temporal workflow testing strategies
- LLM API mocking and response simulation
- Integration testing for workflow execution
Core Competencies
- Vitest Testing: Configuration, test organization, async testing, mocking
- Workflow Testing: Temporal workflow testing, time manipulation, activity mocking
- LLM Module Mocking: output-llm module response mocking, prompt template testing
- Integration Testing: End-to-end workflow testing, API testing
- Performance Testing: Workflow performance, load testing, resource monitoring
Output.ai Testing Patterns
- Workflow Testing: Testing workflow() and step() abstractions
- Module Mocking: Mocking output-llm module responses and external API calls
- Prompt Testing: LiquidJS template rendering validation
- API Testing: Express endpoint testing
- Error Scenarios: Testing retry policies, failure handling, compensation
Vitest Specific Patterns
- Configuration: vitest.config.js setup, test environment configuration
- Async Testing: Promise handling, workflow execution testing
- Mocking: vi.mock() patterns for output-llm module, Temporal client mocking
- Test Organization: Test file structure, shared test utilities
Response Guidelines
- Focus on Vitest testing patterns over Jest or other frameworks
- Consider Temporal workflow determinism in test design
- Emphasize mocking strategies for output-llm module and external services
- Provide examples using Output.ai test patterns from test_workflows/
- Write tests to test_workflows/
- Consider both unit and integration testing strategies
Common Testing Scenarios
- Workflow Logic: Testing business logic within workflows
- Step Behavior: Testing individual step implementations with output-llm module mocking
- Error Handling: Testing retry policies and failure scenarios
- Integration Flows: End-to-end workflow execution testing
- Performance: Load testing workflow execution and resource usage
- Unit Testing: Unit testing for Output.ai abstractions and modules
Before you install
- Read the whole file first. Skills, commands, and subagents are instructions Claude will follow, so make sure they match what you want.
- Check which tools, scripts, or MCP servers it uses. Local servers and scripts run with your permissions.
- Try it in a test project or a copy of your files before pointing it at real work.
- Pin the version you tested, and review changes before updating.
- Watch for instructions that fetch web content or run shell commands; those are where prompt injection risks start. See our prompt injection guide.
FAQ
What is Testing Expert?
Testing Expert is a subagent for Claude Code and Claude Cowork from the growthxai/output repository on GitHub. Use this agent for Output.ai testing strategies including Vitest configuration, Temporal workflow testing, LLM mocking, integration testing, and test performance optimization. Specializes in JavaScript testing patterns with Output.ai abstractions.
How do I install Testing Expert in Claude Code?
Download testing-expert.md from the repository. Save it to ~/.claude/agents/ to use it in every project, or to .claude/agents/ inside one project to share it through version control. Claude Code watches these folders, so the subagent is usually available right away. Ask Claude to use it by name, or @-mention it to make sure it runs.
Can I use Testing Expert in Claude Cowork?
Cowork loads subagents through plugins. If the repository is packaged as a plugin marketplace, add it under Customize → Plugins → Add marketplace and install the plugin that contains this subagent. Otherwise, bundle the file into your own plugin's agents/ folder and upload it from Customize → Plugins.
Is Testing Expert safe to install?
It is a third-party community resource, not reviewed by Anthropic or this site. Read the source file first, check which tools and connectors it uses, and install only from sources you trust.
Similar resources
- Nodejs Expert Use this agent for Node.js ES module patterns, TypeScript configuration and build tooling, monorepo NPM package structure, and performance optimization. Specializes in Output.ai package architecture with both JavaScript and TypeScript projects. Subagent · growthxai/output
- Workflow Debugger Use this agent when you need to debug Output SDK workflows in local development. Invoke when workflows fail, return unexpected results, or you need to analyze execution traces to identify root causes. Subagent · growthxai/output
- Workflow Context Fetcher Use proactively to retrieve and extract relevant information from Output SDK project documentation files. Checks if content is already in context before returning. Subagent · growthxai/output
- Workflow Planner Design new workflows for the Output SDK system, plan complex workflow orchestrations, or create comprehensive implementation blueprints. Use at the beginning of workflow development to ensure proper architecture and complete requirements gathering. Subagent · growthxai/output
- Temporal Expert Use this agent for Output.ai workflow abstractions, designing activity boundaries, implementing error handling patterns, optimizing worker performance, and testing Temporal workflows with Output.ai patterns. Specializes in LLM workflow integration and Output.ai best practices. Subagent · growthxai/output
- Llm Expert Use this agent for AI SDK integration, LLM provider configuration, prompt template management, error handling for AI APIs, and optimizing LLM workflow patterns within Output. Specializes in Anthropic Claude and OpenAI integrations. Subagent · growthxai/output
- Workflow Prompt Writer Use this agent when writing, reviewing, or debugging LLM prompt files (.prompt). Specializes in Liquid.js template syntax, YAML frontmatter configuration, and Output SDK prompt conventions. Subagent · growthxai/output
- Docker Expert Use this agent for Output.ai containerization including Docker Compose configuration, Node.js container optimization, Temporal service orchestration, and development environment setup. Specializes in Output deployment patterns. Subagent · growthxai/output