1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ========================== 3 ==========================
4 Frequently Asked Questions 4 Frequently Asked Questions
5 ========================== 5 ==========================
6 6
7 How is this different from Autotest, kselftest !! 7 How is this different from Autotest, kselftest, etc?
8 ============================================== !! 8 ====================================================
9 KUnit is a unit testing framework. Autotest, k 9 KUnit is a unit testing framework. Autotest, kselftest (and some others) are
10 not. 10 not.
11 11
12 A `unit test <https://martinfowler.com/bliki/U 12 A `unit test <https://martinfowler.com/bliki/UnitTest.html>`_ is supposed to
13 test a single unit of code in isolation and he !! 13 test a single unit of code in isolation, hence the name. A unit test should be
14 test should be the finest granularity of testi !! 14 the finest granularity of testing and as such should allow all possible code
15 code paths to be tested in the code under test !! 15 paths to be tested in the code under test; this is only possible if the code
16 code under test is small and does not have any !! 16 under test is very small and does not have any external dependencies outside of
17 the test's control like hardware. 17 the test's control like hardware.
18 18
19 There are no testing frameworks currently avai 19 There are no testing frameworks currently available for the kernel that do not
20 require installing the kernel on a test machin !! 20 require installing the kernel on a test machine or in a VM and all require
21 testing frameworks require tests to be written !! 21 tests to be written in userspace and run on the kernel under test; this is true
22 kernel under test. This is true for Autotest, !! 22 for Autotest, kselftest, and some others, disqualifying any of them from being
23 disqualifying any of them from being considere !! 23 considered unit testing frameworks.
24 24
25 Does KUnit support running on architectures ot 25 Does KUnit support running on architectures other than UML?
26 ============================================== 26 ===========================================================
27 27
28 Yes, mostly. !! 28 Yes, well, mostly.
29 29
30 For the most part, the KUnit core framework (w !! 30 For the most part, the KUnit core framework (what you use to write the tests)
31 can compile to any architecture. It compiles l !! 31 can compile to any architecture; it compiles like just another part of the
32 kernel and runs when the kernel boots, or when 32 kernel and runs when the kernel boots, or when built as a module, when the
33 module is loaded. However, there is infrastru !! 33 module is loaded. However, there is some infrastructure,
34 (``tools/testing/kunit/kunit.py``) that might !! 34 like the KUnit Wrapper (``tools/testing/kunit/kunit.py``) that does not support
35 (see :ref:`kunit-on-qemu`). !! 35 other architectures.
36 36
37 In short, yes, you can run KUnit on other arch !! 37 In short, this means that, yes, you can run KUnit on other architectures, but
38 more work than using KUnit on UML. !! 38 it might require more work than using KUnit on UML.
39 39
40 For more information, see :ref:`kunit-on-non-u 40 For more information, see :ref:`kunit-on-non-uml`.
41 41
42 .. _kinds-of-tests: !! 42 What is the difference between a unit test and these other kinds of tests?
43 !! 43 ==========================================================================
44 What is the difference between a unit test and <<
45 ============================================== <<
46 Most existing tests for the Linux kernel would 44 Most existing tests for the Linux kernel would be categorized as an integration
47 test, or an end-to-end test. 45 test, or an end-to-end test.
48 46
49 - A unit test is supposed to test a single uni !! 47 - A unit test is supposed to test a single unit of code in isolation, hence the
50 test should be the finest granularity of tes !! 48 name. A unit test should be the finest granularity of testing and as such
51 possible code paths to be tested in the code !! 49 should allow all possible code paths to be tested in the code under test; this
52 if the code under test is small and does not !! 50 is only possible if the code under test is very small and does not have any
53 outside of the test's control like hardware. !! 51 external dependencies outside of the test's control like hardware.
54 - An integration test tests the interaction be 52 - An integration test tests the interaction between a minimal set of components,
55 usually just two or three. For example, some 53 usually just two or three. For example, someone might write an integration
56 test to test the interaction between a drive 54 test to test the interaction between a driver and a piece of hardware, or to
57 test the interaction between the userspace l 55 test the interaction between the userspace libraries the kernel provides and
58 the kernel itself. However, one of these tes !! 56 the kernel itself; however, one of these tests would probably not test the
59 entire kernel along with hardware interactio 57 entire kernel along with hardware interactions and interactions with the
60 userspace. 58 userspace.
61 - An end-to-end test usually tests the entire 59 - An end-to-end test usually tests the entire system from the perspective of the
62 code under test. For example, someone might 60 code under test. For example, someone might write an end-to-end test for the
63 kernel by installing a production configurat 61 kernel by installing a production configuration of the kernel on production
64 hardware with a production userspace and the 62 hardware with a production userspace and then trying to exercise some behavior
65 that depends on interactions between the har 63 that depends on interactions between the hardware, the kernel, and userspace.
66 64
67 KUnit is not working, what should I do? !! 65 KUnit isn't working, what should I do?
68 ======================================= !! 66 ======================================
69 67
70 Unfortunately, there are a number of things wh 68 Unfortunately, there are a number of things which can break, but here are some
71 things to try. 69 things to try.
72 70
73 1. Run ``./tools/testing/kunit/kunit.py run`` !! 71 1. Try running ``./tools/testing/kunit/kunit.py run`` with the ``--raw_output``
74 parameter. This might show details or error 72 parameter. This might show details or error messages hidden by the kunit_tool
75 parser. 73 parser.
76 2. Instead of running ``kunit.py run``, try ru 74 2. Instead of running ``kunit.py run``, try running ``kunit.py config``,
77 ``kunit.py build``, and ``kunit.py exec`` i 75 ``kunit.py build``, and ``kunit.py exec`` independently. This can help track
78 down where an issue is occurring. (If you t 76 down where an issue is occurring. (If you think the parser is at fault, you
79 can run it manually against ``stdin`` or a !! 77 can run it manually against stdin or a file with ``kunit.py parse``.)
80 3. Running the UML kernel directly can often r !! 78 3. Running the UML kernel directly can often reveal issues or error messages
81 ``kunit_tool`` ignores. This should be as s !! 79 kunit_tool ignores. This should be as simple as running ``./vmlinux`` after
82 after building the UML kernel (for example, !! 80 building the UML kernel (e.g., by using ``kunit.py build``). Note that UML
83 Note that UML has some unusual requirements !! 81 has some unusual requirements (such as the host having a tmpfs filesystem
84 filesystem mounted), and has had issues in !! 82 mounted), and has had issues in the past when built statically and the host
85 the host has KASLR enabled. (On older host !! 83 has KASLR enabled. (On older host kernels, you may need to run ``setarch
86 ``setarch `uname -m` -R ./vmlinux`` to disa !! 84 `uname -m` -R ./vmlinux`` to disable KASLR.)
87 4. Make sure the kernel .config has ``CONFIG_K 85 4. Make sure the kernel .config has ``CONFIG_KUNIT=y`` and at least one test
88 (e.g. ``CONFIG_KUNIT_EXAMPLE_TEST=y``). kun 86 (e.g. ``CONFIG_KUNIT_EXAMPLE_TEST=y``). kunit_tool will keep its .config
89 around, so you can see what config was used 87 around, so you can see what config was used after running ``kunit.py run``.
90 It also preserves any config changes you mi 88 It also preserves any config changes you might make, so you can
91 enable/disable things with ``make ARCH=um m 89 enable/disable things with ``make ARCH=um menuconfig`` or similar, and then
92 re-run kunit_tool. 90 re-run kunit_tool.
93 5. Try to run ``make ARCH=um defconfig`` befor 91 5. Try to run ``make ARCH=um defconfig`` before running ``kunit.py run``. This
94 may help clean up any residual config items 92 may help clean up any residual config items which could be causing problems.
95 6. Finally, try running KUnit outside UML. KUn 93 6. Finally, try running KUnit outside UML. KUnit and KUnit tests can be
96 built into any kernel, or can be built as a 94 built into any kernel, or can be built as a module and loaded at runtime.
97 Doing so should allow you to determine if U 95 Doing so should allow you to determine if UML is causing the issue you're
98 seeing. When tests are built-in, they will 96 seeing. When tests are built-in, they will execute when the kernel boots, and
99 modules will automatically execute associat 97 modules will automatically execute associated tests when loaded. Test results
100 can be collected from ``/sys/kernel/debug/k 98 can be collected from ``/sys/kernel/debug/kunit/<test suite>/results``, and
101 can be parsed with ``kunit.py parse``. For !! 99 can be parsed with ``kunit.py parse``. For more details, see "KUnit on
>> 100 non-UML architectures" in Documentation/dev-tools/kunit/usage.rst.
102 101
103 If none of the above tricks help, you are alwa 102 If none of the above tricks help, you are always welcome to email any issues to
104 kunit-dev@googlegroups.com. 103 kunit-dev@googlegroups.com.
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