XCTest/XCTest.h not found on old projects built in Xcode 6
Note: This may not be needed for any projects created in Xcode 7.
CocoaPods had a fix for this here and here
In order to fix this for any CocoaPod dependencies you need to add the following to FRAMEWORK_SEARCH_PATHS in any Pod target that requires XCTest (e.g. Kiwi, Specta, FBSnapshotTestCase, etc).
$(PLATFORM_DIR)/Developer/Library/Frameworks
This will allow you to reference XCTest in any dependencies you may have. This may be fixed in a future update of CocoaPods, or the Pod you are referencing, so you may want to remove it later.
It is not detrimental to earlier versions of Xcode so should be safe to use.