Csharp Testing

This gives Claude solid patterns for testing .NET apps with xUnit, FluentAssertions, and NSubstitute. You get concrete examples for unit tests with proper AAA structure, parameterized tests with Theory, mocking patterns that actually work, and integration tests using WebApplicationFactory and Testcontainers for real databases. It covers test data builders, project organization, and calls out common mistakes like testing implementation details or using Thread.Sleep. Activate this when writing new tests, reviewing coverage, or setting up test infrastructure. The examples are production-ready, not toy code, which makes it immediately useful for real codebases.

skills.sh installs: 3.6K
GitHub stars: 229.1K
last updated: Jul 14, 2026

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Install

$ npx -y skills add affaan-m/everything-claude-code --skill csharp-testing --agent claude-code

Installs into .claude/skills of the current project.

Files

C# Testing Patterns

Comprehensive testing patterns for .NET applications using xUnit, FluentAssertions, and modern testing practices.

When to Activate

Writing new tests for C# code
Reviewing test quality and coverage
Setting up test infrastructure for .NET projects
Debugging flaky or slow tests

Test Framework Stack

Tool	Purpose
xUnit	Test framework (preferred for .NET)
FluentAssertions	Readable assertion syntax
NSubstitute or Moq	Mocking dependencies
Testcontainers	Real infrastructure in integration tests
WebApplicationFactory	ASP.NET Core integration tests
Bogus	Realistic test data generation

Unit Test Structure

Arrange-Act-Assert

public sealed class OrderServiceTests
{
    private readonly IOrderRepository _repository = Substitute.For<IOrderRepository>();
    private readonly ILogger<OrderService> _logger = Substitute.For<ILogger<OrderService>>();
    private readonly OrderService _sut;

    public OrderServiceTests()
    {
        _sut = new OrderService(_repository, _logger);
    }

SKILL.md on GitHub