I have the following in my unit test .pch file to allow my unit tests to find the right bundle for the localization files and this was working fine until I upgraded to Xcode8.
#define NSLocalizedString(key, comment) [[NSBundle bundleWithIdentifier:@"Tests-Unit"] localizedStringForKey:(key) value:@"" table:nil]
Ambiguous expansion of macro NSLocalizedString
@testable import ProjectName
File 'MyFile.swift' is part of module 'ProjectName'; ignoring import.
I eventually got it all working again. I wrote about the steps here: https://myioscache.wordpress.com/2016/11/03/setting-up-unit-tests-xcode-8/