If every change that went into qtdeclarative had to be tested with its dependent modules, then we could catch a lot more bugs and save a lot of time. Even if I still have to fix these issues, at least I will then know exactly which change caused it, rather than have to bisect, etc., and the person who wrote the patch can give me a heads up: "hey, a test in qtquickcontrols2 failed, how should we fix this?"