Unit testing in .NET and .NET 5
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?
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
- Unit testing parallelism
- Measuring and improving Code Coverage
- LAB: Implementing a library with testing
When software development first came to life. People that wanted to start developing, obviously had no prior
knowledge. Thus, everyone started applying their own ways of how they thought software should be written. The
SOLID principles were introduced by Robert C. Martin (a.k.a Uncle Bob) in 2000. The intention of these principles is
to make software designs more understandable, easier to maintain and extend. These principles are essential for
every developer to know, because it will help them in writing better code an better understanding other code that
was written with these principles in mind.
- S - Single Responsibility
- O - Open/Closed
- L - Liskov Substitution
- I - Interface Segregation
- D - Dependency Inversion
More loose coupling using 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 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: MOQ and Microsoft Fakes.
Building Stubs and Mocks can be a lot of work without an Isolation Framework. MOQ is an isolation framework that
allows you to easily build the Fake objects you need for building great
And how do you test 'untestable' code? Code where dependencies have been glued into the class you want to test? Then
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 MOQ
- Checking arguments and return values
- Using Linq to Mocks
- What makes Microsoft Fakes so special
- Testing legacy/untestable code
- Building Stubs and Mocks with Fakes
- LAB: Using MOQ
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 wether 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
- 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 everyting 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
Writing solid, maintainable code that works. This is what every developer wants. This guides you into the art of unit
testing, where you learn to build testable code and various techniques to give your code a good spin. With unit
testing, comes unit testing frameworks. We'll discuss how unit testing frameworks work and how they help you.
Frameworks that will be considered are MSTest and XUnit. Of course we will also observe the need for Stub
and Mock objects. Once you have your unit tests ready you will want to run them automatically,
for example to do regression testing, using Continous Integration. At the end of this course you will go
home with a solid and practical understanding of unit testing and how to apply this in real life. U2U is known for
its real-life approuch to training, so each chapter is accompanied with lots of hands-on labs.
This course is intended for experienced programmers who are very familiar with VB.NET or C# and have a working
experience with the .NET (Framework or .NET 5).