Using Nunit without creating a separate project

I am creating one web application that has a structure as shown in the following image:

I have all the entities and data warehouse files in a folder App_Code. those. A separate project layer is not created. I want to use Nunit for unit testing. But as for NUnit testing, I need projectname.dlland my web application will not create a dll. I do not know how to test my methods.

If I create a separate project for unit tests, I cannot reference the data store and other files in this project. Please suggest how I can use Nunit in this case.