Question: How to properly leverage the DistributedApplicationTestingBuilder.CreateAsync<TEntryPoint>()

[BenjaminCharlton]

I'm working on a new Aspire feature that I hope will be accepted as a Pull Request by the Aspire team.
(See an explanation and my progress here, if interested: #4785)

However, I'm struggling with my unit tests. I'm trying to use the CreateAsync method of the DistributedApplicationTestingBuilder to get a mock distributed application

var distributedApplicationBuilder = await DistributedApplicationTestingBuilder.CreateAsync<BlazorFluentUI_AppHost>();

It was working fine in my own test project in my own solution, where I was passing the type of a recently created AppHost project as the value of T. However, when I copied my unit tests into the Aspire solution (\tests\Aspire.Hosting.Tests) some of them started failing. I tried various values of T, including TestingAppHost1_AppHost (which is a distributed application host project already referenced by the Aspire.Hosting.Tests project.

In all cases above, I got the message:

System.InvalidOperationException : The entry point exited without building a DistributedApplication.

Please could you tell me what class I can use to bootstrap DistributedApplicationTestingBuilder to use in my unit tests?

Thanks for your help!

Benjamin