I have a .NET core MVC rest service. I have a controller I wish to test. This controller has a constructor argument of IOptions where AppSettings is my class for config setting
I discovered the answer shortly after posting the question.
use Helper class Microsoft.Extensions.Options.Options
Creates a wrapper around an instance of TOptions to return itself as IOptions
AppSettings appSettings = new AppSettings() { ConnectionString = "..." };
IOptions<AppSettings> options = Options.Create(appSettings);
MyController controller = new MyController(options);