1 .. SPDX-License-Identifier: GPL-2.0 2 3 =================================================== 4 The Kernel Test Anything Protocol (KTAP), version 1 5 =================================================== 6 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. 15 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 20 aid human debugging. 21 22 KTAP output is built from four different types of lines: 23 - Version lines 24 - Plan lines 25 - Test case result lines 26 - Diagnostic lines 27 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. 33 34 Version lines 35 ------------- 36 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. 39 40 For example: 41 - "KTAP version 1" 42 - "TAP version 13" 43 - "TAP version 14" 44 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. 48 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. 52 53 Plan lines 54 ---------- 55 56 A test plan provides the number of tests (or subtests) in the KTAP output. 57 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. 60 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. 64 65 Test case result lines 66 ---------------------- 67 68 Test case result lines indicate the final status of a test. 69 They are required and must have the format: 70 71 .. code-block:: none 72 73 <result> <number> [<description>][ # [<directive>] [<diagnostic data>]] 74 75 The result can be either "ok", which indicates the test case passed, 76 or "not ok", which indicates that the test case failed. 77 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. 81 82 The description is a description of the test, generally the name of 83 the test, and can be any string of characters other than # or a 84 newline. The description is optional, but recommended. 85 86 The directive and any diagnostic data is optional. If either are present, they 87 must follow a hash sign, "#". 88 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" 93 result. 94 95 Currently accepted directives are: 96 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) 109 110 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. 113 114 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 116 separator. 117 118 Example result lines include:: 119 120 ok 1 test_case_name 121 122 The test "test_case_name" passed. 123 124 :: 125 126 not ok 1 test_case_name 127 128 The test "test_case_name" failed. 129 130 :: 131 132 ok 1 test # SKIP necessary dependency unavailable 133 134 The test "test" was SKIPPED with the diagnostic message "necessary dependency 135 unavailable". 136 137 :: 138 139 not ok 1 test # TIMEOUT 30 seconds 140 141 The test "test" timed out, with diagnostic data "30 seconds". 142 143 :: 144 145 ok 5 check return code # rcode=0 146 147 The test "check return code" passed, with additional diagnostic data “rcode=0” 148 149 150 Diagnostic lines 151 ---------------- 152 153 If tests wish to output any further information, they should do so using 154 "diagnostic lines". Diagnostic lines are optional, freeform text, and are 155 often used to describe what is being tested and any intermediate results in 156 more detail than the final result and diagnostic data line provides. 157 158 Diagnostic lines are formatted as "# <diagnostic_description>", where the 159 description can be any string. Diagnostic lines can be anywhere in the test 160 output. As a rule, diagnostic lines regarding a test are directly before the 161 test result line for that test. 162 163 Note that most tools will treat unknown lines (see below) as diagnostic lines, 164 even if they do not start with a "#": this is to capture any other useful 165 kernel output which may help debug the test. It is nevertheless recommended 166 that tests always prefix any diagnostic output they have with a "#" character. 167 168 Unknown lines 169 ------------- 170 171 There may be lines within KTAP output that do not follow the format of one of 172 the four formats for lines described above. This is allowed, however, they will 173 not influence the status of the tests. 174 175 This is an important difference from TAP. Kernel tests may print messages 176 to the system console or a log file. Both of these destinations may contain 177 messages either from unrelated kernel or userspace activity, or kernel 178 messages from non-test code that is invoked by the test. The kernel code 179 invoked by the test likely is not aware that a test is in progress and 180 thus can not print the message as a diagnostic message. 181 182 Nested tests 183 ------------ 184 185 In KTAP, tests can be nested. This is done by having a test include within its 186 output an entire set of KTAP-formatted results. This can be used to categorize 187 and group related tests, or to split out different results from the same test. 188 189 The "parent" test's result should consist of all of its subtests' results, 190 starting with another KTAP version line and test plan, and end with the overall 191 result. If one of the subtests fail, for example, the parent test should also 192 fail. 193 194 Additionally, all lines in a subtest should be indented. One level of 195 indentation is two spaces: " ". The indentation should begin at the version 196 line and should end before the parent test's result line. 197 198 "Unknown lines" are not considered to be lines in a subtest and thus are 199 allowed to be either indented or not indented. 200 201 An example of a test with two nested subtests: 202 203 :: 204 205 KTAP version 1 206 1..1 207 KTAP version 1 208 1..2 209 ok 1 test_1 210 not ok 2 test_2 211 # example failed 212 not ok 1 example 213 214 An example format with multiple levels of nested testing: 215 216 :: 217 218 KTAP version 1 219 1..2 220 KTAP version 1 221 1..2 222 KTAP version 1 223 1..2 224 not ok 1 test_1 225 ok 2 test_2 226 not ok 1 test_3 227 ok 2 test_4 # SKIP 228 not ok 1 example_test_1 229 ok 2 example_test_2 230 231 232 Major differences between TAP and KTAP 233 -------------------------------------- 234 235 ================================================== ========= =============== 236 Feature TAP KTAP 237 ================================================== ========= =============== 238 yaml and json in diagnosic message ok not recommended 239 TODO directive ok not recognized 240 allows an arbitrary number of tests to be nested no yes 241 "Unknown lines" are in category of "Anything else" yes no 242 "Unknown lines" are incorrect allowed 243 ================================================== ========= =============== 244 245 The TAP14 specification does permit nested tests, but instead of using another 246 nested version line, uses a line of the form 247 "Subtest: <name>" where <name> is the name of the parent test. 248 249 Example KTAP output 250 -------------------- 251 :: 252 253 KTAP version 1 254 1..1 255 KTAP version 1 256 1..3 257 KTAP version 1 258 1..1 259 # test_1: initializing test_1 260 ok 1 test_1 261 ok 1 example_test_1 262 KTAP version 1 263 1..2 264 ok 1 test_1 # SKIP test_1 skipped 265 ok 2 test_2 266 ok 2 example_test_2 267 KTAP version 1 268 1..3 269 ok 1 test_1 270 # test_2: FAIL 271 not ok 2 test_2 272 ok 3 test_3 # SKIP test_3 skipped 273 not ok 3 example_test_3 274 not ok 1 main_test 275 276 This output defines the following hierarchy: 277 278 A single test called "main_test", which fails, and has three subtests: 279 - "example_test_1", which passes, and has one subtest: 280 281 - "test_1", which passes, and outputs the diagnostic message "test_1: initializing test_1" 282 283 - "example_test_2", which passes, and has two subtests: 284 285 - "test_1", which is skipped, with the explanation "test_1 skipped" 286 - "test_2", which passes 287 288 - "example_test_3", which fails, and has three subtests 289 290 - "test_1", which passes 291 - "test_2", which outputs the diagnostic line "test_2: FAIL", and fails. 292 - "test_3", which is skipped with the explanation "test_3 skipped" 293 294 Note that the individual subtests with the same names do not conflict, as they 295 are found in different parent tests. This output also exhibits some sensible 296 rules for "bubbling up" test results: a test fails if any of its subtests fail. 297 Skipped tests do not affect the result of the parent test (though it often 298 makes sense for a test to be marked skipped if _all_ of its subtests have been 299 skipped). 300 301 See also: 302 --------- 303 304 - The TAP specification: 305 https://testanything.org/tap-version-13-specification.html 306 - The (stagnant) TAP version 14 specification: 307 https://github.com/TestAnything/Specification/blob/tap-14-specification/specification.md 308 - The kselftest documentation: 309 Documentation/dev-tools/kselftest.rst 310 - The KUnit documentation: 311 Documentation/dev-tools/kunit/index.rst
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.