I propose to add option (in administrative console) for searching (on Front-End) all typed keyword inside single category item record. For now if I type "test case" I will get all items, that contain "test" and all items, that contain "case". When I type "test +case", then only items, that contain both keywords will be found. This new option will make search act like "+" was used between all typed keywords.
This was implemented somewhere, by modifying kSearchHelper class.