The other answer here is very comprehensive and accurate. I first got interested because it has a good test story, the tests are built with the system and you can just run them. FreeBSD has ported some of this now, but without the rump kernel (which lets you run the kernel you are testing in userspace) it is not nearly as effective.
Now we have it set up so you can compile kernel plus libraries plus userspace into a single binary (in a few minutes of build time) I am looking at more test strategies - kernel+userspace fuzzing for example should be possible.
The Coverity scan score for NetBSD is 0.32, vs Linux at 0.66, and that is including the whole base system (gdb has a lot of problems) - the project has been working on this type of issue for ages.
The codebase is easy to use elsewhere, it is used in lots of other operating systems eg Minix, Android, QNX, Genode - the portability really helps here, it is not just different architectures but you can cross compile from any other operating system, and it supports both clang and gcc as system compilers (and partial support for pcc).
Now we have it set up so you can compile kernel plus libraries plus userspace into a single binary (in a few minutes of build time) I am looking at more test strategies - kernel+userspace fuzzing for example should be possible.
The Coverity scan score for NetBSD is 0.32, vs Linux at 0.66, and that is including the whole base system (gdb has a lot of problems) - the project has been working on this type of issue for ages.
The codebase is easy to use elsewhere, it is used in lots of other operating systems eg Minix, Android, QNX, Genode - the portability really helps here, it is not just different architectures but you can cross compile from any other operating system, and it supports both clang and gcc as system compilers (and partial support for pcc).