Testing Skill for Claude

Testing & TDD Skills

Test-driven development workflows and testing infrastructure for Apple platform apps. Works with both new and existing codebases.

When This Skill Activates

Use this skill when the user:

• Wants to do TDD (test-driven development) with AI-generated code
• Needs to add tests before refactoring existing code
• Wants to fix a bug using the red-green-refactor cycle
• Needs test infrastructure (factories, mocks, contracts)
• Asks about snapshot/visual regression testing
• Wants to ensure AI-generated code is correct via tests
• Wants deterministic gates around agent-written code (architecture invariants, coverage floors, mutation audits)

Available Skills

For Existing Codebases

characterization-test-generator/

Capture current behavior of existing code before refactoring. Generates tests that document what code actually does (not what it should do), giving you a safety net for AI-assisted refactoring.

tdd-bug-fix/

Reproduce-first bug fix workflow. Write a failing test that demonstrates the bug, then fix it. Ensures the bug never regresses — critical when AI generates fixes.

tdd-refactor-guard/

Pre-refactor safety checklist. Verifies test coverage exists before allowing AI to touch existing code. Prevents the "refactor without a safety net" problem.

For New Code

tdd-feature/

Red-green-refactor scaffold for new features. Generates the failing test first, then guides implementation to make it pass, then refactors. The core TDD workflow.

test-contract/

Protocol/interface test suites. Define the contract (e.g., "any DataStore must handle empty state, single item, 100 items, and errors"), and it generates a test suite any implementation must pass.

Infrastructure

snapshot-test-setup/

SwiftUI visual regression testing using swift-snapshot-testing. Generates snapshot test boilerplate, configuration, and CI integration.

test-data-factory/

Test fixture factories for your models. Makes writing tests faster by eliminating boilerplate data setup. Supports Builder pattern and static factory methods.

integration-test-scaffold/

Cross-module test harness with mock servers, in-memory stores, and test configuration. For testing networking + persistence + business logic together.

flow-walkthrough/

Drive each user flow in the Simulator (XCUITest + per-step screenshots), audit the navigation graph for dead-ends, and run a human discoverability check.

Deterministic Gates

fitness-functions/

Architecture fitness functions — tests that enforce a project's hard rules (module import boundaries, offline guarantees, count/copy contracts) from inside its own test target. Turns prose constraints into exit codes.

coverage-ratchet/

Coverage floor that only rises: a committed baseline the app target's line coverage may never drop below, gated by a generated xccov script. Includes an advisory CRAP report (complexity × uncovered).

mutation-testing/

EXPERIMENTAL, advisory-only muter setup scoped to engine targets — surviving mutants reveal covered-but-unasserted code. Never a merge gate; includes the manual deliberate-break fallback.

How to Use

• Identify whether user is working on new code or existing code
• Read the relevant skill's SKILL.md for detailed workflow
• Detect project context (testing framework, architecture, existing tests)
• Generate tests following the skill's workflow
• Verify tests compile and run

Relationship to test-generator

The generators/test-generator/ skill generates test boilerplate (unit, integration, UI tests). These testing skills are complementary — they focus on workflows and methodology (TDD cycle, characterization testing, contracts) rather than just test file generation.

Cross-reference:

• Use test-generator for "add tests to this class"
• Use testing/tdd-feature for "I want to TDD this new feature"
• Use testing/characterization-test-generator for "I need to safely refactor this"
• Use testing/tdd-bug-fix for "fix this bug and make sure it never comes back"