Use when designing or reviewing test doubles — the stand-in objects that replace real collaborators in a test: the five-kind taxonomy (dummy, stub, spy, fake, mock) from Meszaros's xUnit Test Patterns, the difference between state verification (Detroit-school, classicist) and interaction verification (London-school, mockist) and how it determines which doubles fit, the cost of doubles (fragility, false confidence, divergence from real behavior), the role of fakes as the under-used middle ground, the verifywith relationship to test-driven-development, and the heuristics for when to use a real collaborator instead of any double. Do NOT use for choosing test levels or what to test (use testing-strategy), the design discipline of writing tests first (use test-driven-development), specific mocking-library API choice (library docs), or general production stubs and feature flags (use feature-gating or domain-specific skills).
Install with
Claude CodeCodexCursorGitHub CopilotGemini CLI
Supported by the Atlas install prompt. Skill-specific requirements vary.
Skill stats
Skills1CategoryEngineeringStars0
About this skill
Use when designing or reviewing test doubles — the stand-in objects that replace real collaborators in a test: the five-kind taxonomy (dummy, stub, spy, fake, mock) from Meszaros's xUnit Test Patterns, the difference between state verification (Detroit-school, classicist) and interaction verification (London-school, mockist) and how it determines which doubles fit, the cost of doubles (fragility, false confidence, divergence from real behavior), the role of fakes as the under-used middle ground, the verifywith relationship to test-driven-development, and the heuristics for when to use a real collaborator instead of any double. Do NOT use for choosing test levels or what to test (use testing-strategy), the design discipline of writing tests first (use test-driven-development), specific mocking-library API choice (library docs), or general production stubs and feature flags (use feature-gating or domain-specific skills).
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Use when designing or reviewing test doubles — the stand-in objects that replace real collaborators in a test: the five-kind taxonomy (dummy, stub, spy, fake, mock) from Meszaros's xUnit Test Patterns, the difference between state verification (Detroit-school, classicist) and interaction verification (London-school, mockist) and how it determines which doubles fit, the cost of doubles (fragility, false confidence, divergence from real behavior), the role of fakes as the under-used middle ground, the verify_with relationship to test-driven-development, and the heuristics for when to use a real collaborator instead of any double. Do NOT use for choosing test levels or what to test (use testing-strategy), the design discipline of writing tests first (use test-driven-development), specific mocking-library API choice (library docs), or general production stubs and feature flags (use feature-gating or domain-specific skills).
About this listing
Category
Engineering
Reported license
Not specified
Listing language (estimated)
English
Review status
Not individually reviewed
Agent compatibility
Atlas installation supports Claude Code, Codex, and Cursor. Skill-specific dependencies and features are checked during setup.
Claude Code
Codex
Cursor
GitHub Copilot
Gemini CLI