as wikipedia's database gets used to test sem and search tools, open source codes are used for developing testing quality in code already. its out there, accessable and available en mass. i know tony hoare (ms research) does it for his verifying compiler idea. open trusted computing does the same (hp, ibm,amd, infineon, novell/suse ) and then you have qualoss ...

so maybe one day os or foss will be declared at least as best tested codebase in regard to quality. as far as i understand those projects all of them are building code databases under the label: quality proofed.