The kernel self-test framework (kselftest)
has been a part of the kernel for some time now; a relatively recent
proposal for a kernel unit-testing framework,
called KUnit,
has left some wondering why both exist. In a lengthy discussion thread about
KUnit, the justification for adding another testing
framework to the kernel was debated. While there are different use cases
for kselftest and KUnit, there was concern about fragmenting the kernel-testing
landscape.

Source: LWN.net – [$] How many kernel test frameworks?