Testing without simulator using xctool

I'm trying to run unit tests without the simulator using xctool. I set the 'Host Application' to None in the test target's General tab, following the directions from this comment .

When I run xctool -project MyProject.xcodeproj/ -scheme MyProject test I get this error.

<unknown>:0: failed: caught "NSInvalidArgumentException",
"Could not find a storyboard named 'Main' in bundle NSBundle 
</Applications/http://ift.tt/1iLY0Su
Developer/SDKs/http://ift.tt/29nr7Qu; (loaded)"

I made sure that Main.storyboard is a member of the test target. Why is this happening and how can I fix it?