Effective Unit Testing

Unit testing in .NET

Every developer want clean code that works. So how does one get to maintainable and working code? And moreover: keep it working.

• What every developer wants: Quality code that works; and keeps on working
• Finding bugs: not just in code. - Or how NASA lost a 125.000.000$ Mars orbiter
• What is unit testing? And what is a good unit test?
• Understanding the difference between a unit test and an integration test
• Test Driven Development - Should you be doing it?
• Role-playing: Marge, Homer and Bart
• The Triple-A of unit testing - and what has cooking to do with this?
• Given-When-Then

Unit testing with Visual Studio with MSTest and xUnit

When Unit Testing, you will have to decide on frameworks. There are several ones out there, which one do I need? Visual Studio comes with a built in framework called MSTest, but you also have others, like the popular xUnit. In this module, we will discuss pros and cons of these frameworks, and go into some best practices. How do I know if I have tested enough? With code coverage you can see which paths in your code you have tested, and easily discover untested conditional logic.

• MSUnit - Built-in into Visual Studio
• Building and running Unit Tests with MSUnit
• Using the Test Explorer Window
• Using Test Settings
• Live unit testing with Visual Studio
• Unit Testing best practices with xUnit
• Facts and Theories
• Running Unit tests in parallel, or not
• Fluent Assertions
• Measuring and improving Code Coverage
• LAB: Implementing a library with testing

More loose coupling using the art of Dependency Injection

When writing code, you have to make sure you are not introducing unnecessary dependencies on other objects. Dependencies will just cost you on the long run since they are harder to maintain, not easily testable, exchangeable, ... . If you need to depend on another, then depend on the interface. Interfaces describe the dependency, but do not force it. Now, you don't want those dependencies to be filled hard coded and this is where dependency injection (DI) can help you. Dependency injection can help you at runtime dynamically deciding which implementations to plug into the dependencies.

• What is tight coupling and how to prevent it?
• Using Inversion of Control (IoC) containers.
• Constructor and Property injection.
• Microsoft.Extensions.DependencyInjection as an example.

Writing testable code

If you want your code to be testable, you have to engineer your code for testing. You will learn about Stubs and Mocks, and how to replace dependencies that might interfere with testing.

• Testing dependencies - and the art of writing testable code
• The difference between a Fake, a Stub and a Mock
• How to replace dependencies with stub and mock objects
• The Extract and Override pattern
• How the MVVM pattern facilitates UI testing
• Replacing configuration in tests
• LAB: Use Extract and Override to test legacy code

Isolation Frameworks: NSubstitute and Microsoft Fakes.

Building Stubs and Mocks can be a lot of work without an Isolation Framework. NSubstitute is an isolation framework that allows you to easily build the Fake objects you need for building great tests. And how do you test 'untestable' code? Code where dependencies have been glued into the class you want to test? Then you need some magic: Microsoft Fakes. This product allows you to replace any class's implementation, making it easier to test legacy code and other difficult to test code.

• Understanding Isolation Frameworks
• Building Stubs and Mocks with NSubstitute
• Checking arguments and return values
• What makes Microsoft Fakes so special
• Testing legacy/untestable code
• Building Stubs and Mocks with Fakes
• LAB: Using NSubstitute

Unit Testing ASP.NET Core Web Applications

When creating modern web applications with ASP.NET MVC, it's not that straightforward to unit test the Controllers and Views. How does one validate whether the ActionResult returned by the Controller action is the one you wanted, as well as whether the View is correct.

• Challenges when unit testing MVC applications
• Writing unit test for your MVC controllers
• Unit testing your views
• Unit testing ApiControllers
• Faking data access
• Using the ASP.NET Core testing framework
• End-to-end testing
• LAB: Implementing integration and end-to-end tests

Automatic Regression Testing

So your software works! Great! But how do you know if it will work next week, or next month? Did you break something adding some new cool feature? Test everything again? Of course, but now we will make a machine do it automatically every time a team member makes a change.

• What is a regression?
• Using an automated build system
• Continuous integration
• Running integration tests
• Automatic regression tests
• Automatically running your regression tests using GitHub Actions