Xamarin application anatomy

When developing a Xamarin.Forms application, the essentials of the application includes the target platform projects – which act as a harness to initialize the Xamarin.Forms framework and application, as well as the native rendering or API implementations – and a platform-agnostic project that contains the Xamarin.Forms views, as well as the abstractions, so that the custom components can be implemented on platform-specific projects.

As the project grows in size, developers will need to create a separate project that would only contain the view-model and platform-agnostic services implementation. In this case, the project would become the main target of the unit testing process, since this layer does not depend on the UI elements or platform services directly. Additionally, a separate project can be used to share data transfer object (DTO) models between the services layer and the client applications. In a setup like this, the overall architectural layout will look similar to the following:

In some implementations where platform-specific APIs need to be tested, platform-specific unit tests are used, which are executed on the target platform rather than the development platform itself.