What problem does it solve? AI agents are hard to test because LLM outputs are non-deterministic and real API calls are expensive. This Skill provides a structured procedure for building a complete agent test suite — from free mocked unit tests through cheap integration tests to nightly quality evals — so regressions in tool calls, routing, and output quality are caught before production. ## Core Features & Use Cases - Three-Tier Test Pyramid: Designs unit (fully mocked, free), integration (real cheap model), and eval (quality metrics) tiers with cost-aware CI separation. - Tool Call Verification: Tests tool schemas, tool selection, and argument correctness without calling the LLM, using mock factories for OpenAI, Anthropic, and Mistral SDKs. - Eval Framework Setup: Configures promptfoo, DeepEval, Braintrust, or LangSmith with working examples for agentic metrics like ToolCorrectness and TaskCompletion. - Use Case: After refactoring an agent's prompt, run pytest -m unit to verify tool selection logic for free, then trigger the nightly eval suite to detect quality regressions against snapshot baselines. ## Quick Start Ask the agent to set up a test suite for your agent project, specifying your framework, LLM provider, and whether you need unit, integration, or eval tiers.