How to unit test an app extension on Xcode 6

I have reported the bug to Apple. And sadly, the answer is that the keyboard extension is not support unit test now. The answer comes from Apple:

• It's not currently supported to run unit tests inside an app extension
• Instead, factor the code you want to test into a framework and test the code there
• Link the framework into your extension

Just ran into similar issues trying to unit test an extension. Independently did exactly the same thing the author tried with Bundle Loader pointing to .appx path with no success of course. I really did not like the idea of creating a separate framework just for testing so I ended up of adding testable source into the extension test target. It is really simple if you don't have too many source files in your extension:

1. Select you extension test target in Project settings
2. Go to Build Phases
3. Expand Compile Sources
4. Click +
5. Add source files with your testable code.
6. Build for Testing

Why it works:

Once you add extension sources into your extension test target, XCode is going to double reference each of them and compile in both the normal extension build and the test build thus eliminating linking issues.

Are there any drawbacks?

You will have to manually synchronize the source file list in the extension test target. Whenever you add/remove files in the extension target, you may need to do the same in its test target.