Testing C# (.NET) Applications. The Complete Guide

The book "Testing C# (.NET) Applications" is a practical guide to creating high-quality and reliable code on the .NET platform. The author, Alexey Vetrov, shares years of experience in developing and testing industrial applications, ranging from simple unit tests to complex integration and E2E testing scenarios.

What is this book about?

The publication covers all key aspects of testing in the C# and .NET ecosystem:

• Fundamentals of unit testing: xUnit, NUnit, MSTest — choosing a framework, writing your first tests, Arrange-Act-Assert.
• Mocks and stubs: Moq, NSubstitute, FakeItEasy — isolating dependencies, testing without databases and external services.
• Testing ASP.NET Core: controllers, middleware, minimal APIs, integration tests with WebApplicationFactory.
• Working with databases: Entity Framework Core, TestContainers, in-memory providers, testing repositories.
• TDD (Test-Driven Development): red-green-refactor, practical examples, how TDD improves architecture.
• Parameterized and theory tests: InlineData, MemberData, ClassData, combinatorial testing.
• Code Coverage and code quality: configuring Coverlet, Fine Code Coverage, metric analysis.
• Continuous Integration (CI/CD): running tests in GitHub Actions, Azure DevOps, setting up reports.

Who is this book for?

• C# developers of any level who want to master the culture of testing.
• Teams migrating to .NET 8/9 and wanting to implement automated testing.
• Tech leads and architects responsible for code quality and regression testing.
• Anyone who wants to reduce the number of bugs in production and speed up the release cycle.

What will you learn by reading this book?

• How to write maintainable and readable tests that don't break with every change.
• How to properly isolate tests using mocks and stubs.
• How to test web applications on ASP.NET Core, including authentication and gRPC.
• How to integrate tests into a CI/CD pipeline and get coverage reports.
• How to apply TDD on real projects without slowing down development.
• How to avoid common anti-patterns: brittle tests, testing implementation, excessive mocking.

The book contains many ready-to-use code examples and practical exercises to reinforce the material. All examples are relevant for .NET 8 and .NET 9, and are also compatible with previous versions (.NET 6, 7).

"Testing C# (.NET) Applications" is not just a reference book, but a desktop companion for every .NET developer striving for professional growth and creating software you can trust.