I have an existing project that I am trying to add unit tests to. I'm on Xcode 10.1 and project is purely in Swift.

I start by clicking on "New Target..." In the first dialog I am able to choose the project but the dialog box for "Target to be tested" is grayed out.

I have tried to go ahead and add the test target without choosing and this results in my test bundle not being able to find my existing classes - "No such Module error"

Here is the dialog for adding the test bundle:

Not sure what I'm doing wrong to prevent the this selection

Thanks for any help!