1 .. SPDX-License-Identifier: GPL-2.0
3 ===================================================
4 The Kernel Test Anything Protocol (KTAP), version 1
5 ===================================================
7 TAP, or the Test Anything Protocol is a format for specifying test results used
8 by a number of projects. It's website and specification are found at this `link
9 <https://testanything.org/>`_. The Linux Kernel largely uses TAP output for test
10 results. However, Kernel testing frameworks have special needs for test results
11 which don't align with the original TAP specification. Thus, a "Kernel TAP"
12 (KTAP) format is specified to extend and alter TAP to support these use-cases.
13 This specification describes the generally accepted format of KTAP as it is
14 currently used in the kernel.
16 KTAP test results describe a series of tests (which may be nested: i.e., test
17 can have subtests), each of which can contain both diagnostic data -- e.g., log
18 lines -- and a final result. The test structure and results are
19 machine-readable, whereas the diagnostic data is unstructured and is there to
22 KTAP output is built from four different types of lines:
25 - Test case result lines
28 In general, valid KTAP output should also form valid TAP output, but some
29 information, in particular nested test results, may be lost. Also note that
30 there is a stagnant draft specification for TAP14, KTAP diverges from this in
31 a couple of places (notably the "Subtest" header), which are described where
32 relevant later in this document.
37 All KTAP-formatted results begin with a "version line" which specifies which
38 version of the (K)TAP standard the result is compliant with.
45 Note that, in KTAP, subtests also begin with a version line, which denotes the
46 start of the nested test results. This differs from TAP14, which uses a
47 separate "Subtest" line.
49 While, going forward, "KTAP version 1" should be used by compliant tests, it
50 is expected that most parsers and other tooling will accept the other versions
51 listed here for compatibility with existing tests and frameworks.
56 A test plan provides the number of tests (or subtests) in the KTAP output.
58 Plan lines must follow the format of "1..N" where N is the number of tests or subtests.
59 Plan lines follow version lines to indicate the number of nested tests.
61 While there are cases where the number of tests is not known in advance -- in
62 which case the test plan may be omitted -- it is strongly recommended one is
63 present where possible.
65 Test case result lines
66 ----------------------
68 Test case result lines indicate the final status of a test.
69 They are required and must have the format:
73 <result> <number> [<description>][ # [<directive>] [<diagnostic data>]]
75 The result can be either "ok", which indicates the test case passed,
76 or "not ok", which indicates that the test case failed.
78 <number> represents the number of the test being performed. The first test must
79 have the number 1 and the number then must increase by 1 for each additional
80 subtest within the same test at the same nesting level.
82 The description is a description of the test, generally the name of
83 the test, and can be any string of words (can't include #). The
84 description is optional, but recommended.
86 The directive and any diagnostic data is optional. If either are present, they
87 must follow a hash sign, "#".
89 A directive is a keyword that indicates a different outcome for a test other
90 than passed and failed. The directive is optional, and consists of a single
91 keyword preceding the diagnostic data. In the event that a parser encounters
92 a directive it doesn't support, it should fall back to the "ok" / "not ok"
95 Currently accepted directives are:
97 - "SKIP", which indicates a test was skipped (note the result of the test case
98 result line can be either "ok" or "not ok" if the SKIP directive is used)
99 - "TODO", which indicates that a test is not expected to pass at the moment,
100 e.g. because the feature it is testing is known to be broken. While this
101 directive is inherited from TAP, its use in the kernel is discouraged.
102 - "XFAIL", which indicates that a test is expected to fail. This is similar
103 to "TODO", above, and is used by some kselftest tests.
104 - “TIMEOUT”, which indicates a test has timed out (note the result of the test
105 case result line should be “not ok” if the TIMEOUT directive is used)
106 - “ERROR”, which indicates that the execution of a test has failed due to a
107 specific error that is included in the diagnostic data. (note the result of
108 the test case result line should be “not ok” if the ERROR directive is used)
110 The diagnostic data is a plain-text field which contains any additional details
111 about why this result was produced. This is typically an error message for ERROR
112 or failed tests, or a description of missing dependencies for a SKIP result.
114 The diagnostic data field is optional, and results which have neither a
115 directive nor any diagnostic data do not need to include the "#" field
118 Example result lines include:
124 The test "test_case_name" passed.
128 not ok 1 test_case_name
130 The test "test_case_name" failed.
134 ok 1 test # SKIP necessary dependency unavailable
136 The test "test" was SKIPPED with the diagnostic message "necessary dependency
141 not ok 1 test # TIMEOUT 30 seconds
143 The test "test" timed out, with diagnostic data "30 seconds".
147 ok 5 check return code # rcode=0
149 The test "check return code" passed, with additional diagnostic data “rcode=0”
155 If tests wish to output any further information, they should do so using
156 "diagnostic lines". Diagnostic lines are optional, freeform text, and are
157 often used to describe what is being tested and any intermediate results in
158 more detail than the final result and diagnostic data line provides.
160 Diagnostic lines are formatted as "# <diagnostic_description>", where the
161 description can be any string. Diagnostic lines can be anywhere in the test
162 output. As a rule, diagnostic lines regarding a test are directly before the
163 test result line for that test.
165 Note that most tools will treat unknown lines (see below) as diagnostic lines,
166 even if they do not start with a "#": this is to capture any other useful
167 kernel output which may help debug the test. It is nevertheless recommended
168 that tests always prefix any diagnostic output they have with a "#" character.
173 There may be lines within KTAP output that do not follow the format of one of
174 the four formats for lines described above. This is allowed, however, they will
175 not influence the status of the tests.
177 This is an important difference from TAP. Kernel tests may print messages
178 to the system console or a log file. Both of these destinations may contain
179 messages either from unrelated kernel or userspace activity, or kernel
180 messages from non-test code that is invoked by the test. The kernel code
181 invoked by the test likely is not aware that a test is in progress and
182 thus can not print the message as a diagnostic message.
187 In KTAP, tests can be nested. This is done by having a test include within its
188 output an entire set of KTAP-formatted results. This can be used to categorize
189 and group related tests, or to split out different results from the same test.
191 The "parent" test's result should consist of all of its subtests' results,
192 starting with another KTAP version line and test plan, and end with the overall
193 result. If one of the subtests fail, for example, the parent test should also
196 Additionally, all lines in a subtest should be indented. One level of
197 indentation is two spaces: " ". The indentation should begin at the version
198 line and should end before the parent test's result line.
200 "Unknown lines" are not considered to be lines in a subtest and thus are
201 allowed to be either indented or not indented.
203 An example of a test with two nested subtests:
216 An example format with multiple levels of nested testing:
230 not ok 1 example_test_1
234 Major differences between TAP and KTAP
235 --------------------------------------
237 ================================================== ========= ===============
239 ================================================== ========= ===============
240 yaml and json in diagnosic message ok not recommended
241 TODO directive ok not recognized
242 allows an arbitrary number of tests to be nested no yes
243 "Unknown lines" are in category of "Anything else" yes no
244 "Unknown lines" are incorrect allowed
245 ================================================== ========= ===============
247 The TAP14 specification does permit nested tests, but instead of using another
248 nested version line, uses a line of the form
249 "Subtest: <name>" where <name> is the name of the parent test.
261 # test_1: initializing test_1
266 ok 1 test_1 # SKIP test_1 skipped
274 ok 3 test_3 # SKIP test_3 skipped
275 not ok 3 example_test_3
278 This output defines the following hierarchy:
280 A single test called "main_test", which fails, and has three subtests:
281 - "example_test_1", which passes, and has one subtest:
283 - "test_1", which passes, and outputs the diagnostic message "test_1: initializing test_1"
285 - "example_test_2", which passes, and has two subtests:
287 - "test_1", which is skipped, with the explanation "test_1 skipped"
288 - "test_2", which passes
290 - "example_test_3", which fails, and has three subtests
292 - "test_1", which passes
293 - "test_2", which outputs the diagnostic line "test_2: FAIL", and fails.
294 - "test_3", which is skipped with the explanation "test_3 skipped"
296 Note that the individual subtests with the same names do not conflict, as they
297 are found in different parent tests. This output also exhibits some sensible
298 rules for "bubbling up" test results: a test fails if any of its subtests fail.
299 Skipped tests do not affect the result of the parent test (though it often
300 makes sense for a test to be marked skipped if _all_ of its subtests have been
306 - The TAP specification:
307 https://testanything.org/tap-version-13-specification.html
308 - The (stagnant) TAP version 14 specification:
309 https://github.com/TestAnything/Specification/blob/tap-14-specification/specification.md
310 - The kselftest documentation:
311 Documentation/dev-tools/kselftest.rst
312 - The KUnit documentation:
313 Documentation/dev-tools/kunit/index.rst