- DO use extension methods for assertions
- DO favor the Shouldly assertion library over a test framework’s built-in static assertions
Most test frameworks come with their own built-in assertion classes. They are often based on NUnit’s model, where assertions work as static method calls:
These were appropriate at the time NUnit was first released, but later C# versions gave us a much more useful alternative. Shouldly allows us to use extension methods:
These extension methods are more natural to write and to read, and we can augment the built-in assertions with application-specific shorthand, simply by defining our own extension methods with the “ShouldXyz” style of method naming.
Among .NET assertion libraries, Shouldly has a simple API, is actively maintained, and works well for .NET Framework and .NET Core.