Do you use IApiMarker with WebApplicationFactory?

The WebApplicationFactory class is used for bootstrapping an application in memory for functional end to end tests. As part of the initialization of the factory you need to reference a type from the application project.

Typically in the past you'd want to use your Startup or Program classes, the introduction of top-level statements changes how you'd reference those types, so we pivot for consistency.

Top level statements allows for a cleaner Program class, but it also means you can't reference it directly without some additional changes.

Option 1 - Using InternalsVisibleTo attribute

Adding the InternalsVisibleTo attribute to the csproj is a way that you'd be able to reference the Program class from your test project.

This small change leads to a long road of pain:

1. Your WebApplicationFactory needs to be internal
2. Which means you need to make your tests internal and
3. In turn add an InternalsVisibleTo tag to your test project for the test runner to be able to access the tests.

Option 2 - public partial program class

A much quicker option to implement is to create a partial class of the Program class and make it public.

This approach means you don't need to do all the InternalsVisibleTo setup, but does mean you are adding extra none application code to your program file which is what top level statements is trying to avoid.

Option 3 - Using an IApiMarker interface (recommended)

The IApiMarker interface is a simple interface that is used to reference the application project.

namespace RulesApi;

// This marker interface is required for functional testing using WebApplicationFactory.
// See https://www.ssw.com.au/rules/use-iapimarker-with-webapplicationfactory/
public interface IApiMarker
{
}

Using the IApiMarker interface allows you reference your application project in a consistent way, the approach is the same when you use top level statements or standard Program.Main entry points.