KUnit: A new unit testing framework for Linux Kernel

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On Tuesday, Google engineer Brendan Higgins announced an experimental set of 31 patches by introducing KUnit as a new Linux kernel unit testing framework to help preserve and improve the quality of the kernel’s code.

KUnit is a lightweight unit testing and mocking framework designed for the Linux kernel. Unit tests necessarily have finer granularity, they are able to test all code paths easily solving the classic problem of difficulty in exercising error handling code.

KUnit is heavily inspired by JUnit, Python’s unittest.mock, and Googletest/Googlemock for C++. KUnit provides facilities for defining unit test cases, grouping related test cases into test suites, providing common infrastructure for running tests, mocking, spying, and much more.

Brenden writes, “It does not require installing the kernel on a test machine or in a VM and does not require tests to be written in userspace running on a host kernel. Additionally, KUnit is fast: From invocation to completion KUnit can run several dozen tests in under a second. Currently, the entire KUnit test suite for KUnit runs in under a second from the initial invocation (build time excluded).”

When asked if KUnit will replace the other testing frameworks for the Linux Kernel, Brenden denied it, saying, “Most existing tests for the Linux kernel are end-to-end tests, which have their place. A well tested system has lots of unit tests, a reasonable number of integration tests, and some end-to-end tests. KUnit is just trying to address the unit test space which is currently not being addressed.”

To know more about KUnit in detail, read Brendan Higgins’ email threads.