The reason upstreaming it is considered extremely good really doesn’t have to do with unit testing or really exactly with testing at all. The issue, as stated e

The reason upstreaming it is considered extremely good really doesn’t have to do with unit testing or really exactly with testing at all. The issue, as stated eloquently by the parent of your post, is that without it being upstreamed, it’s Nvidia’s problem to fix any issues caused by one of their dependencies in the kernel changing, where as if it’s upstreamed, it’s only maybe partially their responsibility (main burden is on whoever changed the dependency).