Csharp Testing

This covers the practical side of testing .NET applications with xUnit, FluentAssertions, and NSubstitute or Moq. You get patterns for unit tests with proper AAA structure, parameterized tests with Theory attributes, integration testing using WebApplicationFactory, and Testcontainers for real database tests against Postgres. The examples show actual code for mocking repositories, building test data with the builder pattern, and organizing test projects by layer. It skips the philosophy and gives you copy-pasteable setups for the common scenarios like API endpoint testing and repository integration tests. The anti-patterns table at the end is incomplete in the source but the rest is solid reference material when you need to set up or review test infrastructure.

skills.sh installs: 5.5K
GitHub stars: 300.3K
last updated: Aug 21, 2026

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Install

$ npx -y skills add affaan-m/ecc --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