Agent-Skills.md

Agent Skills: Scenario-Driven Testing for AI Code Generation

This skill should be used when writing tests, validating features, or needing to verify code works. Triggers on "write tests", "add test coverage", "validate feature", "integration test", "end-to-end", "e2e test", "mock", "unit test". Enforces scenario-driven testing with real dependencies in .scratch/ directory.

UncategorizedID: aiskillstore/marketplace/scenario-testing

Repository

aiskillstore/marketplace
aiskillstore
23014

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pnpm dlx add-skill https://github.com/aiskillstore/marketplace/tree/HEAD/skills/2389-research/scenario-testing

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skills/2389-research/scenario-testing/SKILL.md

Skill Metadata

Name
scenario-testing
Description
This skill should be used when writing tests, validating features, or needing to verify code works. Triggers on "write tests", "add test coverage", "validate feature", "integration test", "end-to-end", "e2e test", "mock", "unit test". Enforces scenario-driven testing with real dependencies in .scratch/ directory.

Scenario-Driven Testing for AI Code Generation

Core Principle

The Iron Law: "NO FEATURE IS VALIDATED UNTIL A SCENARIO PASSES WITH REAL DEPENDENCIES"

Mocks create false confidence. Only scenarios exercising real systems validate that code works.

The Truth Hierarchy

  1. Scenario tests (real system, real data) = truth
  2. Unit tests (isolated) = human comfort only
  3. Mocks = lies hiding bugs

As stated in the principle: "A test that uses mocks is not testing your system. It's testing your assumptions about how dependencies behave."

When to Use This Skill

  • Validating new functionality
  • Before declaring work complete
  • When tempted to use mocks
  • After fixing bugs requiring verification
  • Any time you need to prove code works

Required Practices

1. Write Scenarios in .scratch/

  • Use any language appropriate to the task
  • Exercise the real system end-to-end
  • Zero mocks allowed
  • Must be in .gitignore (never commit)

2. Promote Patterns to scenarios.jsonl

  • Extract recurring scenarios as documented specifications
  • One JSON line per scenario
  • Include: name, description, given/when/then, validates
  • This file IS committed

3. Use Real Dependencies

External APIs must hit actual services (sandbox/test mode acceptable). Mocking any dependency invalidates the scenario.

4. Independence Requirement

Each scenario must run standalone without depending on prior executions. This enables:

  • Parallel execution
  • Prevents hidden ordering dependencies
  • Reliable CI/CD integration

What Makes a Scenario Invalid

A scenario is invalid if it:

  • Contains any mocks whatsoever
  • Uses fake data instead of real storage
  • Depends on another scenario running first
  • Never actually executed to verify it passes

Common Violations to Avoid

Reject these rationalizations:

  • "Just a quick unit test..." - Unit tests don't validate features
  • "Too simple for end-to-end..." - Integration breaks simple things
  • "I'll mock for speed..." - Speed doesn't matter if tests lie
  • "I don't have API credentials..." - Ask your human partner for real ones

Definition of Done

A feature is complete only when:

  1. ✅ A scenario in .scratch/ passes with zero mocks
  2. ✅ Real dependencies are exercised
  3. ✅ .scratch/ remains in .gitignore
  4. ✅ Robust patterns extracted to scenarios.jsonl

Example Workflow

  1. Write scenario - Create .scratch/test-user-registration.py
  2. Use real dependencies - Hit real database, real auth service (test mode)
  3. Run and verify - Execute scenario, confirm it passes
  4. Extract pattern - Document in scenarios.jsonl
  5. Keep .scratch ignored - Never commit scratch scenarios

Why This Matters

  • Unit tests verify isolated logic
  • Integration tests verify components work together
  • Scenario tests verify the system actually works

Only scenario tests prove your feature delivers value to users.