ASP.NET Core Unit test config transformation

Question

I have ASP.NET Core + Unit Tests projects. I running this on the 2 environments

1. local (local environment)
2. azure web app (development environment)

both projects has identical config files appsettings.json

also they have appsettings.Development.json

I expecting when I using "Development" configuration during build process, I will get "transformed" configs for each projects.

By some reason only web project has "transformed" settings after build.

I would like to run unit test during build process on development server but cannot figure out how to apply transformation and use needed connection string to database of the development server