Paths: File paths (shared/ , references/ , ../ln-* ) are relative to skills repo root. If not found at CWD, locate this SKILL.md directory and go up one level for repo root. If shared/ is missing, fetch files via WebFetch from https://raw.githubusercontent.com/levnikolaevich/claude-code-skills/master/skills/{path} .

ln-743-test-infrastructure

Type: L3 Worker Category: 7XX Project Bootstrap

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/ ├── 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.

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).

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

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

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: 3.0.0 Last Updated: 2026-03-18