testing-agents-with-subagents

Testing Agents With Subagents

Overview

This skill applies TDD methodology to agent development — RED (observe failures), GREEN (fix agent definition), REFACTOR (edge cases and robustness) — with subagent dispatch as the execution mechanism.

Test what the agent DOES, not what the prompt SAYS. Evidence-based verification only: capture exact outputs from subagent dispatch, verify every prompt change through testing. Always test via the Task tool, always test via the Task tool rather than reading prompts.

Minimum test counts vary by agent type: Reviewer agents need 6 cases (2 real issues, 2 clean, 1 edge, 1 ambiguous), Implementation agents 5 cases (2 typical, 1 complex, 1 minimal, 1 error), Analysis agents 4 cases (2 standard, 1 edge, 1 malformed), Routing/orchestration 4 cases (2 correct route, 1 ambiguous, 1 invalid). No agent is simple enough to skip testing — get human confirmation before exempting any agent.

Each test runs in a fresh subagent to avoid context pollution. After any fix, re-run ALL test cases to catch regressions. One fix at a time — you cannot determine what changed the outcome with multiple simultaneous fixes.

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Reference Loading Table

Signal	Load These Files	Why
example-driven tasks, errors	examples-and-errors.md	Loads detailed guidance from examples-and-errors.md.
dispatch-and-capture, negative, consistency, A/B, and routing-verification test patterns	testing-patterns.md	Loads detailed guidance from testing-patterns.md.

Instructions

Phase 0: PREPARE — Understand the Agent

Goal: Read the agent definition and understand what it claims to do before writing tests.

Step 1: Read the agent file

# Read agent definition
cat agents/{agent-name}.md

# Read any referenced skills
cat skills/{skill-name}/SKILL.md

Step 2: Identify testable claims

Extract concrete, testable behaviors from the agent definition:

• What inputs does it accept?
• What output structure does it produce?
• What routing triggers should activate it?
• What error conditions does it handle?
• What skills does it invoke?