kunit: add FAQ to documentation
Change-Id: I7e8340ba62cc122a8afa9a30e5915616cce9b1ed
Signed-off-by: Felix Guo <felixguo@google.com>
diff --git a/Documentation/test/faq.rst b/Documentation/test/faq.rst
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+=========================================
+Frequently Asked Questions
+=========================================
+
+.. toctree::
+ :maxdepth: 2
+
+ faq
+
+How is this different from Autotest, kselftest, etc?
+====================================================
+KUnit is a unit testing framework. Autotest, kselftest (and some others) are
+not.
+
+A unit test is supposed to test a single unit of code in isolation, hence the
+name. A unit test should be the finest granularity of testing and as such should
+allow all possible code paths to be tested in the code under test; this is only
+possible if the code under test is very small and does not have any external
+dependencies outside of the test's control like hardware.
+
+There are no testing frameworks currently available for the kernel that do not
+require installing the kernel on a test machine or in a VM and all require
+tests to be written in userspace and run on the kernel under test; this is true
+for Autotest, kselftest, and some others, disqualifying any of them from being
+considered unit testing frameworks.
+
+What is the difference between a unit test and these other kinds of tests?
+==========================================================================
+Mosts existing tests for the Linux kernel would be categorized as an integration
+test, or an end-to-end test.
+
+- A unit test is supposed to test a single unit of code in isolation, hence the
+ name. A unit test should be the finest granularity of testing and as such
+ should allow all possible code paths to be tested in the code under test; this
+ is only possible if the code under test is very small and does not have any
+ external dependencies outside of the test's control like hardware.
+- An integration test tests the interaction between a minimal set of components,
+ usually just two or three. For example, someone might write an integration
+ test to test the interaction between a driver and a piece of hardware, or to
+ test the interaction between the userspace libraries the kernel provides and
+ the kernel itself; however, one of these tests would probably not test the
+ entire kernel along with hardware interactions and interactions with the
+ userspace.
+- An end-to-end test usually tests the entire system from the perspective of the
+ code under test. For example, someone might write an end-to-end test for the
+ kernel by installing a production configuration of the kernel on production
+ hardware with a production userspace and then trying to exercise some behavior
+ that depends on interactions between the hardware, the kernel, and userspace.
diff --git a/Documentation/test/index.rst b/Documentation/test/index.rst
index 4ef0a8d..381386c 100644
--- a/Documentation/test/index.rst
+++ b/Documentation/test/index.rst
@@ -8,6 +8,7 @@
start
usage
api/index
+ faq
What is KUnit?
==============
