Creating unit tests in Uno.UI.UnitTests

Unit tests in Uno.UI.UnitTests (the test runner project at src/Uno.UI.UnitTests/Uno.UI.UnitTests.csproj) run against the Skia build of Uno.UI. They exercise the real cross-platform code path -- the same dependency-property system, layouter, and dispatcher used by Skia at runtime -- not a mock. Any platform-specific behavior (rendering surfaces, native windowing, OS APIs) is provided by the Skia runtime stack itself.

Adding tests here is closest to the 'traditional' unit test experience: you can run tests from the Visual Studio test window pane, easily debug the code you're modifying, etc. This is the ideal place to test platform-independent parts of the API, like dependency property behaviors and XAML-generated code.

If a test requires a hosted Window, real input dispatching, or rendering output (for example, screenshot comparisons or visibility-driven assertions), prefer Uno.UI.RuntimeTests instead -- those tests run inside a hosted SamplesApp on each target platform.

Running tests in Uno.UI.Tests

1. Open and build the Uno.UI solution for the unit tests target.
2. Open Test Explorer from the TEST menu.
3. Tests are listed under Uno.UI.Tests. You can run all tests or a subsection, with or without debugging. (Note: You usually don't need to run Uno.Xaml.Tests tests locally, unless you're making changes to low-level XAML parsing in Uno.Xaml.)

Adding a new test

1. Locate the test class corresponding to the control or class you want to create a test for. If you need to add a new test class, create the file as Namespace_In_Snake_Case/ControlNameTests/Given_ControlName.cs and mark it with the [TestClass] attribute.
2. Add tests for your cases, naming them as When_Your_Scenario and marking each with the [TestMethod] attribute. (For more information about the 'Given-When-Then' naming style, read https://martinfowler.com/bliki/GivenWhenThen.html.)