ln-743-test-infrastructure Skill

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ln-743-test-infrastructure

Type: L3 Worker Category: 7XX Project Bootstrap Parent: ln-740-quality-setup

Sets up testing frameworks, coverage tools, and sample tests for projects.

Purpose & Scope

Does:

Detects project stack to choose appropriate test framework
Creates test configuration files
Sets up coverage reporting with thresholds
Creates sample tests demonstrating patterns
Verifies test suite runs successfully

Does NOT:

Configure linters (ln-741 does this)
Set up pre-commit hooks (ln-742 does this)
Write actual application tests (developers do this)

Supported Stacks

| Technology | Test Framework | Coverage Tool | Config File | |------------|---------------|---------------|-------------| | TypeScript/React | Vitest | v8/Istanbul | vitest.config.ts | | .NET | xUnit | Coverlet | *.Tests.csproj | | Python | pytest | pytest-cov | pytest.ini or pyproject.toml |

Phase 1: Check Existing Tests

Before creating test infrastructure, check what exists.

Files to Check:

| Stack | Test Indicators | |-------|-----------------| | TypeScript | vitest.config.*, jest.config.*, *.test.ts, *.spec.ts | | .NET | *.Tests.csproj, *.IntegrationTests.csproj | | Python | pytest.ini, conftest.py, tests/, test_*.py |

Decision Logic:

If complete test setup exists: SKIP (inform user)
If partial setup: ASK to extend or replace
If no tests: CREATE from templates

Phase 2: Create Test Configuration

TypeScript/React (Vitest)

Create vitest.config.ts:

Use v8 coverage provider (faster than Istanbul)
Configure jsdom environment for React
Set coverage thresholds (80% minimum)
Create setup file for testing-library

Dependencies:

npm install -D vitest @vitest/coverage-v8 @testing-library/react @testing-library/jest-dom jsdom

.NET (xUnit)

Create test project:

dotnet new xunit -n {Project}.Tests
dotnet sln add tests/{Project}.Tests

Dependencies (in .csproj):

Microsoft.NET.Test.Sdk
xunit
xunit.runner.visualstudio
Moq
FluentAssertions
coverlet.collector

Python (pytest)

Add to pyproject.toml or create pytest.ini:

Configure test discovery paths
Set coverage thresholds (80% minimum)
Configure coverage reporting

Dependencies:

pip install pytest pytest-cov pytest-asyncio
# OR with uv:
uv add --dev pytest pytest-cov pytest-asyncio

Phase 3: Create Test Directory Structure

TypeScript

src/
├── components/
│   ├── Button.tsx
│   └── Button.test.tsx  # Co-located tests
├── test/
│   └── setup.ts         # Test setup file

.NET

tests/
├── {Project}.Tests/
│   ├── Controllers/
│   │   └── SampleControllerTests.cs
│   ├── Services/
│   └── {Project}.Tests.csproj
└── {Project}.IntegrationTests/  # Optional

Python

tests/
├── __init__.py
├── conftest.py          # Fixtures
├── unit/
│   └── test_sample.py
└── integration/         # Optional

Phase 4: Create Sample Tests

Create one sample test per stack demonstrating:

AAA pattern (Arrange-Act-Assert)
Test naming conventions
Basic assertions
Framework-specific patterns

TypeScript Sample Test

Shows:

render() from testing-library
screen queries
Jest-dom matchers

.NET Sample Test

Shows:

[Fact] attribute
Moq for mocking
FluentAssertions syntax

Python Sample Test

Shows:

pytest fixtures
assert statements
parametrized tests (optional)

Phase 5: Verify Test Run

After setup, verify tests work.

TypeScript:

npm test
npm run test:coverage

Expected: Sample test passes, coverage report generated

.NET:

dotnet test
dotnet test --collect:"XPlat Code Coverage"

Expected: Sample test passes, coverage collected

Python:

pytest
pytest --cov=src --cov-report=term-missing

Expected: Sample test passes, coverage report shown

On Failure: Check test configuration, dependencies, verify sample test syntax.

Coverage Requirements

| Metric | Minimum | Target | |--------|---------|--------| | Lines | 70% | 80% | | Branches | 70% | 80% | | Functions | 70% | 80% | | Statements | 70% | 80% |

Configure CI to fail if coverage drops below thresholds.

Critical Rules

RULE 1: Coverage thresholds MUST be configured. No exceptions.

RULE 2: Sample tests MUST pass. Don't create broken examples.

RULE 3: Use AAA pattern (Arrange-Act-Assert) in all sample tests.

RULE 4: Co-locate unit tests with source (TypeScript) or use tests/ directory (.NET, Python).

Definition of Done

[ ] Test framework installed and configured
[ ] Coverage tool configured with 80% threshold
[ ] Test directory structure created
[ ] Sample test created and passing
[ ] npm test / dotnet test / pytest runs successfully
[ ] Coverage report generates
[ ] User informed of:
- How to run tests
- Where to add new tests
- Coverage requirements

Reference Files

| File | Purpose | |------|---------| | vitest_template.ts | Vitest config template | | vitest_setup_template.ts | Test setup file | | react_test_template.tsx | React component test | | xunit_csproj_template.xml | .NET test project | | xunit_test_template.cs | xUnit test example | | pytest_config_template.toml | pytest config | | pytest_test_template.py | pytest test example | | testing_guide.md | Testing best practices |

Error Handling

| Error | Cause | Resolution | |-------|-------|------------| | Vitest not found | Not installed | npm install -D vitest | | jsdom errors | Missing dependency | npm install -D jsdom | | xUnit discovery fails | SDK version mismatch | Update Microsoft.NET.Test.Sdk | | pytest not found | Not in PATH | pip install pytest | | Coverage 0% | Wrong source path | Check coverage.include config |

Version: 2.0.0 Last Updated: 2026-01-10

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