Apparently not. It is crazy that they delete a random line of code and don't update or add a single test at the same time. Absolute madness. I wonder what they are doing instead that ensures the Kernel mostly works.
First, they do have unit tests (KUnit). However, I suspect the "real" tests that result in a mostly-working kernel are massive integration tests run independently by companies contributing to Linux. And, of course, actual users running rc and release kernels who report problems (which I suppose is not unlike a stochastic distributed integration testing system).