now in swift 4 you just have to import a briding header into Test target and reference objc-class .h files there...using @testable import nameOfYourApp should work
In Swift there's a message in "Test Target" that states that the bridging header will be removed in newer versions of swift. I'm using mixed objc and swift clasess, but the UnitTest class is a swift file. Using @testable key was there in code
@testable import YourProject
You fix it by adding in your Test area the bridging header with objc headers that your test will use:
#import "Project-Bridging-Header.h"
and deleting the @testable inside your test
import YourProject
Thank you