t / READMEon commit t/README: Document the prereq functions, and 3-arg test_* (9a89789)
   1Core GIT Tests
   2==============
   3
   4This directory holds many test scripts for core GIT tools.  The
   5first part of this short document describes how to run the tests
   6and read their output.
   7
   8When fixing the tools or adding enhancements, you are strongly
   9encouraged to add tests in this directory to cover what you are
  10trying to fix or enhance.  The later part of this short document
  11describes how your test scripts should be organized.
  12
  13
  14Running Tests
  15-------------
  16
  17The easiest way to run tests is to say "make".  This runs all
  18the tests.
  19
  20    *** t0000-basic.sh ***
  21    ok 1 - .git/objects should be empty after git init in an empty repo.
  22    ok 2 - .git/objects should have 3 subdirectories.
  23    ok 3 - success is reported like this
  24    ...
  25    ok 43 - very long name in the index handled sanely
  26    # fixed 1 known breakage(s)
  27    # still have 1 known breakage(s)
  28    # passed all remaining 42 test(s)
  29    1..43
  30    *** t0001-init.sh ***
  31    ok 1 - plain
  32    ok 2 - plain with GIT_WORK_TREE
  33    ok 3 - plain bare
  34
  35Since the tests all output TAP (see http://testanything.org) they can
  36be run with any TAP harness. Here's an example of parallel testing
  37powered by a recent version of prove(1):
  38
  39    $ prove --timer --jobs 15 ./t[0-9]*.sh
  40    [19:17:33] ./t0005-signals.sh ................................... ok       36 ms
  41    [19:17:33] ./t0022-crlf-rename.sh ............................... ok       69 ms
  42    [19:17:33] ./t0024-crlf-archive.sh .............................. ok      154 ms
  43    [19:17:33] ./t0004-unwritable.sh ................................ ok      289 ms
  44    [19:17:33] ./t0002-gitfile.sh ................................... ok      480 ms
  45    ===(     102;0  25/?  6/?  5/?  16/?  1/?  4/?  2/?  1/?  3/?  1... )===
  46
  47prove and other harnesses come with a lot of useful options. The
  48--state option in particular is very useful:
  49
  50    # Repeat until no more failures
  51    $ prove -j 15 --state=failed,save ./t[0-9]*.sh
  52
  53You can also run each test individually from command line, like this:
  54
  55    $ sh ./t3010-ls-files-killed-modified.sh
  56    ok 1 - git update-index --add to add various paths.
  57    ok 2 - git ls-files -k to show killed files.
  58    ok 3 - validate git ls-files -k output.
  59    ok 4 - git ls-files -m to show modified files.
  60    ok 5 - validate git ls-files -m output.
  61    # passed all 5 test(s)
  62    1..5
  63
  64You can pass --verbose (or -v), --debug (or -d), and --immediate
  65(or -i) command line argument to the test, or by setting GIT_TEST_OPTS
  66appropriately before running "make".
  67
  68--verbose::
  69        This makes the test more verbose.  Specifically, the
  70        command being run and their output if any are also
  71        output.
  72
  73--debug::
  74        This may help the person who is developing a new test.
  75        It causes the command defined with test_debug to run.
  76
  77--immediate::
  78        This causes the test to immediately exit upon the first
  79        failed test.
  80
  81--long-tests::
  82        This causes additional long-running tests to be run (where
  83        available), for more exhaustive testing.
  84
  85--valgrind::
  86        Execute all Git binaries with valgrind and exit with status
  87        126 on errors (just like regular tests, this will only stop
  88        the test script when running under -i).  Valgrind errors
  89        go to stderr, so you might want to pass the -v option, too.
  90
  91        Since it makes no sense to run the tests with --valgrind and
  92        not see any output, this option implies --verbose.  For
  93        convenience, it also implies --tee.
  94
  95--tee::
  96        In addition to printing the test output to the terminal,
  97        write it to files named 't/test-results/$TEST_NAME.out'.
  98        As the names depend on the tests' file names, it is safe to
  99        run the tests with this option in parallel.
 100
 101--with-dashes::
 102        By default tests are run without dashed forms of
 103        commands (like git-commit) in the PATH (it only uses
 104        wrappers from ../bin-wrappers).  Use this option to include
 105        the build directory (..) in the PATH, which contains all
 106        the dashed forms of commands.  This option is currently
 107        implied by other options like --valgrind and
 108        GIT_TEST_INSTALLED.
 109
 110--root=<directory>::
 111        Create "trash" directories used to store all temporary data during
 112        testing under <directory>, instead of the t/ directory.
 113        Using this option with a RAM-based filesystem (such as tmpfs)
 114        can massively speed up the test suite.
 115
 116You can also set the GIT_TEST_INSTALLED environment variable to
 117the bindir of an existing git installation to test that installation.
 118You still need to have built this git sandbox, from which various
 119test-* support programs, templates, and perl libraries are used.
 120If your installed git is incomplete, it will silently test parts of
 121your built version instead.
 122
 123When using GIT_TEST_INSTALLED, you can also set GIT_TEST_EXEC_PATH to
 124override the location of the dashed-form subcommands (what
 125GIT_EXEC_PATH would be used for during normal operation).
 126GIT_TEST_EXEC_PATH defaults to `$GIT_TEST_INSTALLED/git --exec-path`.
 127
 128
 129Skipping Tests
 130--------------
 131
 132In some environments, certain tests have no way of succeeding
 133due to platform limitation, such as lack of 'unzip' program, or
 134filesystem that do not allow arbitrary sequence of non-NUL bytes
 135as pathnames.
 136
 137You should be able to say something like
 138
 139    $ GIT_SKIP_TESTS=t9200.8 sh ./t9200-git-cvsexport-commit.sh
 140
 141and even:
 142
 143    $ GIT_SKIP_TESTS='t[0-4]??? t91?? t9200.8' make
 144
 145to omit such tests.  The value of the environment variable is a
 146SP separated list of patterns that tells which tests to skip,
 147and either can match the "t[0-9]{4}" part to skip the whole
 148test, or t[0-9]{4} followed by ".$number" to say which
 149particular test to skip.
 150
 151Note that some tests in the existing test suite rely on previous
 152test item, so you cannot arbitrarily disable one and expect the
 153remainder of test to check what the test originally was intended
 154to check.
 155
 156
 157Naming Tests
 158------------
 159
 160The test files are named as:
 161
 162        tNNNN-commandname-details.sh
 163
 164where N is a decimal digit.
 165
 166First digit tells the family:
 167
 168        0 - the absolute basics and global stuff
 169        1 - the basic commands concerning database
 170        2 - the basic commands concerning the working tree
 171        3 - the other basic commands (e.g. ls-files)
 172        4 - the diff commands
 173        5 - the pull and exporting commands
 174        6 - the revision tree commands (even e.g. merge-base)
 175        7 - the porcelainish commands concerning the working tree
 176        8 - the porcelainish commands concerning forensics
 177        9 - the git tools
 178
 179Second digit tells the particular command we are testing.
 180
 181Third digit (optionally) tells the particular switch or group of switches
 182we are testing.
 183
 184If you create files under t/ directory (i.e. here) that is not
 185the top-level test script, never name the file to match the above
 186pattern.  The Makefile here considers all such files as the
 187top-level test script and tries to run all of them.  A care is
 188especially needed if you are creating a common test library
 189file, similar to test-lib.sh, because such a library file may
 190not be suitable for standalone execution.
 191
 192
 193Writing Tests
 194-------------
 195
 196The test script is written as a shell script.  It should start
 197with the standard "#!/bin/sh" with copyright notices, and an
 198assignment to variable 'test_description', like this:
 199
 200        #!/bin/sh
 201        #
 202        # Copyright (c) 2005 Junio C Hamano
 203        #
 204
 205        test_description='xxx test (option --frotz)
 206
 207        This test registers the following structure in the cache
 208        and tries to run git-ls-files with option --frotz.'
 209
 210
 211Source 'test-lib.sh'
 212--------------------
 213
 214After assigning test_description, the test script should source
 215test-lib.sh like this:
 216
 217        . ./test-lib.sh
 218
 219This test harness library does the following things:
 220
 221 - If the script is invoked with command line argument --help
 222   (or -h), it shows the test_description and exits.
 223
 224 - Creates an empty test directory with an empty .git/objects database
 225   and chdir(2) into it.  This directory is 't/trash
 226   directory.$test_name_without_dotsh', with t/ subject to change by
 227   the --root option documented above.
 228
 229 - Defines standard test helper functions for your scripts to
 230   use.  These functions are designed to make all scripts behave
 231   consistently when command line arguments --verbose (or -v),
 232   --debug (or -d), and --immediate (or -i) is given.
 233
 234
 235End with test_done
 236------------------
 237
 238Your script will be a sequence of tests, using helper functions
 239from the test harness library.  At the end of the script, call
 240'test_done'.
 241
 242
 243Test harness library
 244--------------------
 245
 246There are a handful helper functions defined in the test harness
 247library for your script to use.
 248
 249 - test_expect_success [<prereq>] <message> <script>
 250
 251   Usually takes two strings as parameter, and evaluates the
 252   <script>.  If it yields success, test is considered
 253   successful.  <message> should state what it is testing.
 254
 255   Example:
 256
 257        test_expect_success \
 258            'git-write-tree should be able to write an empty tree.' \
 259            'tree=$(git-write-tree)'
 260
 261   If you supply three parameters the first will be taken to be a
 262   prerequisite, see the test_set_prereq and test_have_prereq
 263   documentation below:
 264
 265        test_expect_success TTY 'git --paginate rev-list uses a pager' \
 266            ' ... '
 267
 268 - test_expect_failure [<prereq>] <message> <script>
 269
 270   This is NOT the opposite of test_expect_success, but is used
 271   to mark a test that demonstrates a known breakage.  Unlike
 272   the usual test_expect_success tests, which say "ok" on
 273   success and "FAIL" on failure, this will say "FIXED" on
 274   success and "still broken" on failure.  Failures from these
 275   tests won't cause -i (immediate) to stop.
 276
 277   Like test_expect_success this function can optionally use a three
 278   argument invocation with a prerequisite as the first argument.
 279
 280 - test_debug <script>
 281
 282   This takes a single argument, <script>, and evaluates it only
 283   when the test script is started with --debug command line
 284   argument.  This is primarily meant for use during the
 285   development of a new test script.
 286
 287 - test_done
 288
 289   Your test script must have test_done at the end.  Its purpose
 290   is to summarize successes and failures in the test script and
 291   exit with an appropriate error code.
 292
 293 - test_tick
 294
 295   Make commit and tag names consistent by setting the author and
 296   committer times to defined stated.  Subsequent calls will
 297   advance the times by a fixed amount.
 298
 299 - test_commit <message> [<filename> [<contents>]]
 300
 301   Creates a commit with the given message, committing the given
 302   file with the given contents (default for both is to reuse the
 303   message string), and adds a tag (again reusing the message
 304   string as name).  Calls test_tick to make the SHA-1s
 305   reproducible.
 306
 307 - test_merge <message> <commit-or-tag>
 308
 309   Merges the given rev using the given message.  Like test_commit,
 310   creates a tag and calls test_tick before committing.
 311
 312 - test_set_prereq SOME_PREREQ
 313
 314   Set a test prerequisite to be used later with test_have_prereq. The
 315   test-lib will set some prerequisites for you, e.g. PERL and PYTHON
 316   which are derived from ./GIT-BUILD-OPTIONS (grep test_set_prereq
 317   test-lib.sh for more). Others you can set yourself and use later
 318   with either test_have_prereq directly, or the three argument
 319   invocation of test_expect_success and test_expect_failure.
 320
 321 - test_have_prereq SOME PREREQ
 322
 323   Check if we have a prerequisite previously set with
 324   test_set_prereq. The most common use of this directly is to skip
 325   all the tests if we don't have some essential prerequisite:
 326
 327        if ! test_have_prereq PERL
 328        then
 329            skip_all='skipping perl interface tests, perl not available'
 330            test_done
 331        fi
 332
 333Tips for Writing Tests
 334----------------------
 335
 336As with any programming projects, existing programs are the best
 337source of the information.  However, do _not_ emulate
 338t0000-basic.sh when writing your tests.  The test is special in
 339that it tries to validate the very core of GIT.  For example, it
 340knows that there will be 256 subdirectories under .git/objects/,
 341and it knows that the object ID of an empty tree is a certain
 34240-byte string.  This is deliberately done so in t0000-basic.sh
 343because the things the very basic core test tries to achieve is
 344to serve as a basis for people who are changing the GIT internal
 345drastically.  For these people, after making certain changes,
 346not seeing failures from the basic test _is_ a failure.  And
 347such drastic changes to the core GIT that even changes these
 348otherwise supposedly stable object IDs should be accompanied by
 349an update to t0000-basic.sh.
 350
 351However, other tests that simply rely on basic parts of the core
 352GIT working properly should not have that level of intimate
 353knowledge of the core GIT internals.  If all the test scripts
 354hardcoded the object IDs like t0000-basic.sh does, that defeats
 355the purpose of t0000-basic.sh, which is to isolate that level of
 356validation in one place.  Your test also ends up needing
 357updating when such a change to the internal happens, so do _not_
 358do it and leave the low level of validation to t0000-basic.sh.