ln-743-test-infrastructure

name	ln-743-test-infrastructure
description	Sets up test infrastructure with Vitest, xUnit, and pytest. Use when adding testing frameworks and sample tests to a project.
license	MIT

Paths: File paths (references/, ../ln-*) are relative to this skill directory.

ln-743-test-infrastructure

Type: L3 Worker Category: 7XX Project Bootstrap

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

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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)

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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

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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:

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

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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

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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/
├── conftest.py          # Shared fixtures (from conftest_template.py)
├── unit/
│   └── test_sample.py
└── integration/         # Optional

For FastAPI/async projects, generate conftest.py from conftest_template.py with shared async HTTP client fixture. Adapt the app import path to match the project.

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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)

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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.

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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.

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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).

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Monitor (2.1.98+): When test verification after scaffold expected >30s, use Monitor. Fallback: Bash(run_in_background=true).

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

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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
conftest_template.py	Shared async fixtures (FastAPI)
testing_guide.md	Testing best practices

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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

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Version: 3.0.0 Last Updated: 2026-03-18