| name | testing |
| description | TDD and testing skills for iOS/macOS apps. Covers characterization tests, TDD workflows, test contracts, snapshot tests, test infrastructure, and deterministic quality gates (fitness functions, coverage ratchet, mutation testing). Use for test-driven development, adding tests to existing code, or building test infrastructure. |
| allowed-tools | ["Read","Write","Edit","Glob","Grep","Bash","AskUserQuestion"] |
| last_verified | "2026-07-24T00:00:00.000Z" |
| review_by | "2027-06-22T00:00:00.000Z" |
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"
