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   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 give DEFAULT_TEST_TARGET=prove on the make command (or define it
  54in config.mak) to cause "make test" to run tests under prove.
  55GIT_PROVE_OPTS can be used to pass additional options, e.g.
  56
  57    $ make DEFAULT_TEST_TARGET=prove GIT_PROVE_OPTS='--timer --jobs 16' test
  58
  59You can also run each test individually from command line, like this:
  60
  61    $ sh ./t3010-ls-files-killed-modified.sh
  62    ok 1 - git update-index --add to add various paths.
  63    ok 2 - git ls-files -k to show killed files.
  64    ok 3 - validate git ls-files -k output.
  65    ok 4 - git ls-files -m to show modified files.
  66    ok 5 - validate git ls-files -m output.
  67    # passed all 5 test(s)
  68    1..5
  69
  70You can pass --verbose (or -v), --debug (or -d), and --immediate
  71(or -i) command line argument to the test, or by setting GIT_TEST_OPTS
  72appropriately before running "make".
  73
  74-v::
  75--verbose::
  76        This makes the test more verbose.  Specifically, the
  77        command being run and their output if any are also
  78        output.
  79
  80--verbose-only=<pattern>::
  81        Like --verbose, but the effect is limited to tests with
  82        numbers matching <pattern>.  The number matched against is
  83        simply the running count of the test within the file.
  84
  85-x::
  86        Turn on shell tracing (i.e., `set -x`) during the tests
  87        themselves. Implies `--verbose`.
  88        Ignored in test scripts that set the variable 'test_untraceable'
  89        to a non-empty value, unless it's run with a Bash version
  90        supporting BASH_XTRACEFD, i.e. v4.1 or later.
  91
  92-d::
  93--debug::
  94        This may help the person who is developing a new test.
  95        It causes the command defined with test_debug to run.
  96        The "trash" directory (used to store all temporary data
  97        during testing) is not deleted even if there are no
  98        failed tests so that you can inspect its contents after
  99        the test finished.
 100
 101-i::
 102--immediate::
 103        This causes the test to immediately exit upon the first
 104        failed test. Cleanup commands requested with
 105        test_when_finished are not executed if the test failed,
 106        in order to keep the state for inspection by the tester
 107        to diagnose the bug.
 108
 109-l::
 110--long-tests::
 111        This causes additional long-running tests to be run (where
 112        available), for more exhaustive testing.
 113
 114-r::
 115--run=<test-selector>::
 116        Run only the subset of tests indicated by
 117        <test-selector>.  See section "Skipping Tests" below for
 118        <test-selector> syntax.
 119
 120--valgrind=<tool>::
 121        Execute all Git binaries under valgrind tool <tool> and exit
 122        with status 126 on errors (just like regular tests, this will
 123        only stop the test script when running under -i).
 124
 125        Since it makes no sense to run the tests with --valgrind and
 126        not see any output, this option implies --verbose.  For
 127        convenience, it also implies --tee.
 128
 129        <tool> defaults to 'memcheck', just like valgrind itself.
 130        Other particularly useful choices include 'helgrind' and
 131        'drd', but you may use any tool recognized by your valgrind
 132        installation.
 133
 134        As a special case, <tool> can be 'memcheck-fast', which uses
 135        memcheck but disables --track-origins.  Use this if you are
 136        running tests in bulk, to see if there are _any_ memory
 137        issues.
 138
 139        Note that memcheck is run with the option --leak-check=no,
 140        as the git process is short-lived and some errors are not
 141        interesting. In order to run a single command under the same
 142        conditions manually, you should set GIT_VALGRIND to point to
 143        the 't/valgrind/' directory and use the commands under
 144        't/valgrind/bin/'.
 145
 146--valgrind-only=<pattern>::
 147        Like --valgrind, but the effect is limited to tests with
 148        numbers matching <pattern>.  The number matched against is
 149        simply the running count of the test within the file.
 150
 151--tee::
 152        In addition to printing the test output to the terminal,
 153        write it to files named 't/test-results/$TEST_NAME.out'.
 154        As the names depend on the tests' file names, it is safe to
 155        run the tests with this option in parallel.
 156
 157--verbose-log::
 158        Write verbose output to the same logfile as `--tee`, but do
 159        _not_ write it to stdout. Unlike `--tee --verbose`, this option
 160        is safe to use when stdout is being consumed by a TAP parser
 161        like `prove`. Implies `--tee` and `--verbose`.
 162
 163--with-dashes::
 164        By default tests are run without dashed forms of
 165        commands (like git-commit) in the PATH (it only uses
 166        wrappers from ../bin-wrappers).  Use this option to include
 167        the build directory (..) in the PATH, which contains all
 168        the dashed forms of commands.  This option is currently
 169        implied by other options like --valgrind and
 170        GIT_TEST_INSTALLED.
 171
 172--root=<directory>::
 173        Create "trash" directories used to store all temporary data during
 174        testing under <directory>, instead of the t/ directory.
 175        Using this option with a RAM-based filesystem (such as tmpfs)
 176        can massively speed up the test suite.
 177
 178--chain-lint::
 179--no-chain-lint::
 180        If --chain-lint is enabled, the test harness will check each
 181        test to make sure that it properly "&&-chains" all commands (so
 182        that a failure in the middle does not go unnoticed by the final
 183        exit code of the test). This check is performed in addition to
 184        running the tests themselves. You may also enable or disable
 185        this feature by setting the GIT_TEST_CHAIN_LINT environment
 186        variable to "1" or "0", respectively.
 187
 188You can also set the GIT_TEST_INSTALLED environment variable to
 189the bindir of an existing git installation to test that installation.
 190You still need to have built this git sandbox, from which various
 191test-* support programs, templates, and perl libraries are used.
 192If your installed git is incomplete, it will silently test parts of
 193your built version instead.
 194
 195When using GIT_TEST_INSTALLED, you can also set GIT_TEST_EXEC_PATH to
 196override the location of the dashed-form subcommands (what
 197GIT_EXEC_PATH would be used for during normal operation).
 198GIT_TEST_EXEC_PATH defaults to `$GIT_TEST_INSTALLED/git --exec-path`.
 199
 200
 201Skipping Tests
 202--------------
 203
 204In some environments, certain tests have no way of succeeding
 205due to platform limitation, such as lack of 'unzip' program, or
 206filesystem that do not allow arbitrary sequence of non-NUL bytes
 207as pathnames.
 208
 209You should be able to say something like
 210
 211    $ GIT_SKIP_TESTS=t9200.8 sh ./t9200-git-cvsexport-commit.sh
 212
 213and even:
 214
 215    $ GIT_SKIP_TESTS='t[0-4]??? t91?? t9200.8' make
 216
 217to omit such tests.  The value of the environment variable is a
 218SP separated list of patterns that tells which tests to skip,
 219and either can match the "t[0-9]{4}" part to skip the whole
 220test, or t[0-9]{4} followed by ".$number" to say which
 221particular test to skip.
 222
 223For an individual test suite --run could be used to specify that
 224only some tests should be run or that some tests should be
 225excluded from a run.
 226
 227The argument for --run is a list of individual test numbers or
 228ranges with an optional negation prefix that define what tests in
 229a test suite to include in the run.  A range is two numbers
 230separated with a dash and matches a range of tests with both ends
 231been included.  You may omit the first or the second number to
 232mean "from the first test" or "up to the very last test"
 233respectively.
 234
 235Optional prefix of '!' means that the test or a range of tests
 236should be excluded from the run.
 237
 238If --run starts with an unprefixed number or range the initial
 239set of tests to run is empty. If the first item starts with '!'
 240all the tests are added to the initial set.  After initial set is
 241determined every test number or range is added or excluded from
 242the set one by one, from left to right.
 243
 244Individual numbers or ranges could be separated either by a space
 245or a comma.
 246
 247For example, to run only tests up to a specific test (21), one
 248could do this:
 249
 250    $ sh ./t9200-git-cvsexport-commit.sh --run='1-21'
 251
 252or this:
 253
 254    $ sh ./t9200-git-cvsexport-commit.sh --run='-21'
 255
 256Common case is to run several setup tests (1, 2, 3) and then a
 257specific test (21) that relies on that setup:
 258
 259    $ sh ./t9200-git-cvsexport-commit.sh --run='1 2 3 21'
 260
 261or:
 262
 263    $ sh ./t9200-git-cvsexport-commit.sh --run=1,2,3,21
 264
 265or:
 266
 267    $ sh ./t9200-git-cvsexport-commit.sh --run='-3 21'
 268
 269As noted above, the test set is built by going through the items
 270from left to right, so this:
 271
 272    $ sh ./t9200-git-cvsexport-commit.sh --run='1-4 !3'
 273
 274will run tests 1, 2, and 4.  Items that come later have higher
 275precedence.  It means that this:
 276
 277    $ sh ./t9200-git-cvsexport-commit.sh --run='!3 1-4'
 278
 279would just run tests from 1 to 4, including 3.
 280
 281You may use negation with ranges.  The following will run all
 282test in the test suite except from 7 up to 11:
 283
 284    $ sh ./t9200-git-cvsexport-commit.sh --run='!7-11'
 285
 286Some tests in a test suite rely on the previous tests performing
 287certain actions, specifically some tests are designated as
 288"setup" test, so you cannot _arbitrarily_ disable one test and
 289expect the rest to function correctly.
 290
 291--run is mostly useful when you want to focus on a specific test
 292and know what setup is needed for it.  Or when you want to run
 293everything up to a certain test.
 294
 295
 296Running tests with special setups
 297---------------------------------
 298
 299The whole test suite could be run to test some special features
 300that cannot be easily covered by a few specific test cases. These
 301could be enabled by running the test suite with correct GIT_TEST_
 302environment set.
 303
 304GIT_TEST_SPLIT_INDEX=<boolean> forces split-index mode on the whole
 305test suite. Accept any boolean values that are accepted by git-config.
 306
 307GIT_TEST_FULL_IN_PACK_ARRAY=<boolean> exercises the uncommon
 308pack-objects code path where there are more than 1024 packs even if
 309the actual number of packs in repository is below this limit. Accept
 310any boolean values that are accepted by git-config.
 311
 312GIT_TEST_OE_SIZE=<n> exercises the uncommon pack-objects code path
 313where we do not cache object size in memory and read it from existing
 314packs on demand. This normally only happens when the object size is
 315over 2GB. This variable forces the code path on any object larger than
 316<n> bytes.
 317
 318GIT_TEST_OE_DELTA_SIZE=<n> exercises the uncommon pack-objects code
 319path where deltas larger than this limit require extra memory
 320allocation for bookkeeping.
 321
 322GIT_TEST_VALIDATE_INDEX_CACHE_ENTRIES=<boolean> checks that cache-tree
 323records are valid when the index is written out or after a merge. This
 324is mostly to catch missing invalidation. Default is true.
 325
 326GIT_TEST_COMMIT_GRAPH=<boolean>, when true, forces the commit-graph to
 327be written after every 'git commit' command, and overrides the
 328'core.commitGraph' setting to true.
 329
 330GIT_TEST_FSMONITOR=$PWD/t7519/fsmonitor-all exercises the fsmonitor
 331code path for utilizing a file system monitor to speed up detecting
 332new or changed files.
 333
 334GIT_TEST_INDEX_VERSION=<n> exercises the index read/write code path
 335for the index version specified.  Can be set to any valid version
 336(currently 2, 3, or 4).
 337
 338GIT_TEST_PRELOAD_INDEX=<boolean> exercises the preload-index code path
 339by overriding the minimum number of cache entries required per thread.
 340
 341GIT_TEST_INDEX_THREADS=<n> enables exercising the multi-threaded loading
 342of the index for the whole test suite by bypassing the default number of
 343cache entries and thread minimums. Setting this to 1 will make the
 344index loading single threaded.
 345
 346Naming Tests
 347------------
 348
 349The test files are named as:
 350
 351        tNNNN-commandname-details.sh
 352
 353where N is a decimal digit.
 354
 355First digit tells the family:
 356
 357        0 - the absolute basics and global stuff
 358        1 - the basic commands concerning database
 359        2 - the basic commands concerning the working tree
 360        3 - the other basic commands (e.g. ls-files)
 361        4 - the diff commands
 362        5 - the pull and exporting commands
 363        6 - the revision tree commands (even e.g. merge-base)
 364        7 - the porcelainish commands concerning the working tree
 365        8 - the porcelainish commands concerning forensics
 366        9 - the git tools
 367
 368Second digit tells the particular command we are testing.
 369
 370Third digit (optionally) tells the particular switch or group of switches
 371we are testing.
 372
 373If you create files under t/ directory (i.e. here) that is not
 374the top-level test script, never name the file to match the above
 375pattern.  The Makefile here considers all such files as the
 376top-level test script and tries to run all of them.  Care is
 377especially needed if you are creating a common test library
 378file, similar to test-lib.sh, because such a library file may
 379not be suitable for standalone execution.
 380
 381
 382Writing Tests
 383-------------
 384
 385The test script is written as a shell script.  It should start
 386with the standard "#!/bin/sh", and an
 387assignment to variable 'test_description', like this:
 388
 389        #!/bin/sh
 390
 391        test_description='xxx test (option --frotz)
 392
 393        This test registers the following structure in the cache
 394        and tries to run git-ls-files with option --frotz.'
 395
 396
 397Source 'test-lib.sh'
 398--------------------
 399
 400After assigning test_description, the test script should source
 401test-lib.sh like this:
 402
 403        . ./test-lib.sh
 404
 405This test harness library does the following things:
 406
 407 - If the script is invoked with command line argument --help
 408   (or -h), it shows the test_description and exits.
 409
 410 - Creates an empty test directory with an empty .git/objects database
 411   and chdir(2) into it.  This directory is 't/trash
 412   directory.$test_name_without_dotsh', with t/ subject to change by
 413   the --root option documented above.
 414
 415 - Defines standard test helper functions for your scripts to
 416   use.  These functions are designed to make all scripts behave
 417   consistently when command line arguments --verbose (or -v),
 418   --debug (or -d), and --immediate (or -i) is given.
 419
 420Do's & don'ts
 421-------------
 422
 423Here are a few examples of things you probably should and shouldn't do
 424when writing tests.
 425
 426Here are the "do's:"
 427
 428 - Put all code inside test_expect_success and other assertions.
 429
 430   Even code that isn't a test per se, but merely some setup code
 431   should be inside a test assertion.
 432
 433 - Chain your test assertions
 434
 435   Write test code like this:
 436
 437        git merge foo &&
 438        git push bar &&
 439        test ...
 440
 441   Instead of:
 442
 443        git merge hla
 444        git push gh
 445        test ...
 446
 447   That way all of the commands in your tests will succeed or fail. If
 448   you must ignore the return value of something, consider using a
 449   helper function (e.g. use sane_unset instead of unset, in order
 450   to avoid unportable return value for unsetting a variable that was
 451   already unset), or prepending the command with test_might_fail or
 452   test_must_fail.
 453
 454 - Check the test coverage for your tests. See the "Test coverage"
 455   below.
 456
 457   Don't blindly follow test coverage metrics; if a new function you added
 458   doesn't have any coverage, then you're probably doing something wrong,
 459   but having 100% coverage doesn't necessarily mean that you tested
 460   everything.
 461
 462   Tests that are likely to smoke out future regressions are better
 463   than tests that just inflate the coverage metrics.
 464
 465 - When a test checks for an absolute path that a git command generated,
 466   construct the expected value using $(pwd) rather than $PWD,
 467   $TEST_DIRECTORY, or $TRASH_DIRECTORY. It makes a difference on
 468   Windows, where the shell (MSYS bash) mangles absolute path names.
 469   For details, see the commit message of 4114156ae9.
 470
 471 - Remember that inside the <script> part, the standard output and
 472   standard error streams are discarded, and the test harness only
 473   reports "ok" or "not ok" to the end user running the tests. Under
 474   --verbose, they are shown to help debug the tests.
 475
 476And here are the "don'ts:"
 477
 478 - Don't exit() within a <script> part.
 479
 480   The harness will catch this as a programming error of the test.
 481   Use test_done instead if you need to stop the tests early (see
 482   "Skipping tests" below).
 483
 484 - Don't use '! git cmd' when you want to make sure the git command
 485   exits with failure in a controlled way by calling "die()".  Instead,
 486   use 'test_must_fail git cmd'.  This will signal a failure if git
 487   dies in an unexpected way (e.g. segfault).
 488
 489   On the other hand, don't use test_must_fail for running regular
 490   platform commands; just use '! cmd'.  We are not in the business
 491   of verifying that the world given to us sanely works.
 492
 493 - Don't feed the output of a git command to a pipe, as in:
 494
 495     git -C repo ls-files |
 496     xargs -n 1 basename |
 497     grep foo
 498
 499   which will discard git's exit code and may mask a crash. In the
 500   above example, all exit codes are ignored except grep's.
 501
 502   Instead, write the output of that command to a temporary
 503   file with ">" or assign it to a variable with "x=$(git ...)" rather
 504   than pipe it.
 505
 506 - Don't use command substitution in a way that discards git's exit
 507   code. When assigning to a variable, the exit code is not discarded,
 508   e.g.:
 509
 510     x=$(git cat-file -p $sha) &&
 511     ...
 512
 513   is OK because a crash in "git cat-file" will cause the "&&" chain
 514   to fail, but:
 515
 516     test "refs/heads/foo" = "$(git symbolic-ref HEAD)"
 517
 518   is not OK and a crash in git could go undetected.
 519
 520 - Don't use perl without spelling it as "$PERL_PATH". This is to help
 521   our friends on Windows where the platform Perl often adds CR before
 522   the end of line, and they bundle Git with a version of Perl that
 523   does not do so, whose path is specified with $PERL_PATH. Note that we
 524   provide a "perl" function which uses $PERL_PATH under the hood, so
 525   you do not need to worry when simply running perl in the test scripts
 526   (but you do, for example, on a shebang line or in a sub script
 527   created via "write_script").
 528
 529 - Don't use sh without spelling it as "$SHELL_PATH", when the script
 530   can be misinterpreted by broken platform shell (e.g. Solaris).
 531
 532 - Don't chdir around in tests.  It is not sufficient to chdir to
 533   somewhere and then chdir back to the original location later in
 534   the test, as any intermediate step can fail and abort the test,
 535   causing the next test to start in an unexpected directory.  Do so
 536   inside a subshell if necessary.
 537
 538 - Don't save and verify the standard error of compound commands, i.e.
 539   group commands, subshells, and shell functions (except test helper
 540   functions like 'test_must_fail') like this:
 541
 542     ( cd dir && git cmd ) 2>error &&
 543     test_cmp expect error
 544
 545   When running the test with '-x' tracing, then the trace of commands
 546   executed in the compound command will be included in standard error
 547   as well, quite possibly throwing off the subsequent checks examining
 548   the output.  Instead, save only the relevant git command's standard
 549   error:
 550
 551     ( cd dir && git cmd 2>../error ) &&
 552     test_cmp expect error
 553
 554 - Don't break the TAP output
 555
 556   The raw output from your test may be interpreted by a TAP harness. TAP
 557   harnesses will ignore everything they don't know about, but don't step
 558   on their toes in these areas:
 559
 560   - Don't print lines like "$x..$y" where $x and $y are integers.
 561
 562   - Don't print lines that begin with "ok" or "not ok".
 563
 564   TAP harnesses expect a line that begins with either "ok" and "not
 565   ok" to signal a test passed or failed (and our harness already
 566   produces such lines), so your script shouldn't emit such lines to
 567   their output.
 568
 569   You can glean some further possible issues from the TAP grammar
 570   (see https://metacpan.org/pod/TAP::Parser::Grammar#TAP-GRAMMAR)
 571   but the best indication is to just run the tests with prove(1),
 572   it'll complain if anything is amiss.
 573
 574
 575Skipping tests
 576--------------
 577
 578If you need to skip tests you should do so by using the three-arg form
 579of the test_* functions (see the "Test harness library" section
 580below), e.g.:
 581
 582    test_expect_success PERL 'I need Perl' '
 583        perl -e "hlagh() if unf_unf()"
 584    '
 585
 586The advantage of skipping tests like this is that platforms that don't
 587have the PERL and other optional dependencies get an indication of how
 588many tests they're missing.
 589
 590If the test code is too hairy for that (i.e. does a lot of setup work
 591outside test assertions) you can also skip all remaining tests by
 592setting skip_all and immediately call test_done:
 593
 594        if ! test_have_prereq PERL
 595        then
 596            skip_all='skipping perl interface tests, perl not available'
 597            test_done
 598        fi
 599
 600The string you give to skip_all will be used as an explanation for why
 601the test was skipped.
 602
 603End with test_done
 604------------------
 605
 606Your script will be a sequence of tests, using helper functions
 607from the test harness library.  At the end of the script, call
 608'test_done'.
 609
 610
 611Test harness library
 612--------------------
 613
 614There are a handful helper functions defined in the test harness
 615library for your script to use.
 616
 617 - test_expect_success [<prereq>] <message> <script>
 618
 619   Usually takes two strings as parameters, and evaluates the
 620   <script>.  If it yields success, test is considered
 621   successful.  <message> should state what it is testing.
 622
 623   Example:
 624
 625        test_expect_success \
 626            'git-write-tree should be able to write an empty tree.' \
 627            'tree=$(git-write-tree)'
 628
 629   If you supply three parameters the first will be taken to be a
 630   prerequisite; see the test_set_prereq and test_have_prereq
 631   documentation below:
 632
 633        test_expect_success TTY 'git --paginate rev-list uses a pager' \
 634            ' ... '
 635
 636   You can also supply a comma-separated list of prerequisites, in the
 637   rare case where your test depends on more than one:
 638
 639        test_expect_success PERL,PYTHON 'yo dawg' \
 640            ' test $(perl -E 'print eval "1 +" . qx[python -c "print 2"]') == "4" '
 641
 642 - test_expect_failure [<prereq>] <message> <script>
 643
 644   This is NOT the opposite of test_expect_success, but is used
 645   to mark a test that demonstrates a known breakage.  Unlike
 646   the usual test_expect_success tests, which say "ok" on
 647   success and "FAIL" on failure, this will say "FIXED" on
 648   success and "still broken" on failure.  Failures from these
 649   tests won't cause -i (immediate) to stop.
 650
 651   Like test_expect_success this function can optionally use a three
 652   argument invocation with a prerequisite as the first argument.
 653
 654 - test_debug <script>
 655
 656   This takes a single argument, <script>, and evaluates it only
 657   when the test script is started with --debug command line
 658   argument.  This is primarily meant for use during the
 659   development of a new test script.
 660
 661 - debug <git-command>
 662
 663   Run a git command inside a debugger. This is primarily meant for
 664   use when debugging a failing test script.
 665
 666 - test_done
 667
 668   Your test script must have test_done at the end.  Its purpose
 669   is to summarize successes and failures in the test script and
 670   exit with an appropriate error code.
 671
 672 - test_tick
 673
 674   Make commit and tag names consistent by setting the author and
 675   committer times to defined state.  Subsequent calls will
 676   advance the times by a fixed amount.
 677
 678 - test_commit <message> [<filename> [<contents>]]
 679
 680   Creates a commit with the given message, committing the given
 681   file with the given contents (default for both is to reuse the
 682   message string), and adds a tag (again reusing the message
 683   string as name).  Calls test_tick to make the SHA-1s
 684   reproducible.
 685
 686 - test_merge <message> <commit-or-tag>
 687
 688   Merges the given rev using the given message.  Like test_commit,
 689   creates a tag and calls test_tick before committing.
 690
 691 - test_set_prereq <prereq>
 692
 693   Set a test prerequisite to be used later with test_have_prereq. The
 694   test-lib will set some prerequisites for you, see the
 695   "Prerequisites" section below for a full list of these.
 696
 697   Others you can set yourself and use later with either
 698   test_have_prereq directly, or the three argument invocation of
 699   test_expect_success and test_expect_failure.
 700
 701 - test_have_prereq <prereq>
 702
 703   Check if we have a prerequisite previously set with test_set_prereq.
 704   The most common way to use this explicitly (as opposed to the
 705   implicit use when an argument is passed to test_expect_*) is to skip
 706   all the tests at the start of the test script if we don't have some
 707   essential prerequisite:
 708
 709        if ! test_have_prereq PERL
 710        then
 711            skip_all='skipping perl interface tests, perl not available'
 712            test_done
 713        fi
 714
 715 - test_external [<prereq>] <message> <external> <script>
 716
 717   Execute a <script> with an <external> interpreter (like perl). This
 718   was added for tests like t9700-perl-git.sh which do most of their
 719   work in an external test script.
 720
 721        test_external \
 722            'GitwebCache::*FileCache*' \
 723            perl "$TEST_DIRECTORY"/t9503/test_cache_interface.pl
 724
 725   If the test is outputting its own TAP you should set the
 726   test_external_has_tap variable somewhere before calling the first
 727   test_external* function. See t9700-perl-git.sh for an example.
 728
 729        # The external test will outputs its own plan
 730        test_external_has_tap=1
 731
 732 - test_external_without_stderr [<prereq>] <message> <external> <script>
 733
 734   Like test_external but fail if there's any output on stderr,
 735   instead of checking the exit code.
 736
 737        test_external_without_stderr \
 738            'Perl API' \
 739            perl "$TEST_DIRECTORY"/t9700/test.pl
 740
 741 - test_expect_code <exit-code> <command>
 742
 743   Run a command and ensure that it exits with the given exit code.
 744   For example:
 745
 746        test_expect_success 'Merge with d/f conflicts' '
 747                test_expect_code 1 git merge "merge msg" B master
 748        '
 749
 750 - test_must_fail [<options>] <git-command>
 751
 752   Run a git command and ensure it fails in a controlled way.  Use
 753   this instead of "! <git-command>".  When git-command dies due to a
 754   segfault, test_must_fail diagnoses it as an error; "! <git-command>"
 755   treats it as just another expected failure, which would let such a
 756   bug go unnoticed.
 757
 758   Accepts the following options:
 759
 760     ok=<signal-name>[,<...>]:
 761       Don't treat an exit caused by the given signal as error.
 762       Multiple signals can be specified as a comma separated list.
 763       Currently recognized signal names are: sigpipe, success.
 764       (Don't use 'success', use 'test_might_fail' instead.)
 765
 766 - test_might_fail [<options>] <git-command>
 767
 768   Similar to test_must_fail, but tolerate success, too.  Use this
 769   instead of "<git-command> || :" to catch failures due to segv.
 770
 771   Accepts the same options as test_must_fail.
 772
 773 - test_cmp <expected> <actual>
 774
 775   Check whether the content of the <actual> file matches the
 776   <expected> file.  This behaves like "cmp" but produces more
 777   helpful output when the test is run with "-v" option.
 778
 779 - test_cmp_rev <expected> <actual>
 780
 781   Check whether the <expected> rev points to the same commit as the
 782   <actual> rev.
 783
 784 - test_line_count (= | -lt | -ge | ...) <length> <file>
 785
 786   Check whether a file has the length it is expected to.
 787
 788 - test_path_is_file <path> [<diagnosis>]
 789   test_path_is_dir <path> [<diagnosis>]
 790   test_path_is_missing <path> [<diagnosis>]
 791
 792   Check if the named path is a file, if the named path is a
 793   directory, or if the named path does not exist, respectively,
 794   and fail otherwise, showing the <diagnosis> text.
 795
 796 - test_when_finished <script>
 797
 798   Prepend <script> to a list of commands to run to clean up
 799   at the end of the current test.  If some clean-up command
 800   fails, the test will not pass.
 801
 802   Example:
 803
 804        test_expect_success 'branch pointing to non-commit' '
 805                git rev-parse HEAD^{tree} >.git/refs/heads/invalid &&
 806                test_when_finished "git update-ref -d refs/heads/invalid" &&
 807                ...
 808        '
 809
 810 - test_write_lines <lines>
 811
 812   Write <lines> on standard output, one line per argument.
 813   Useful to prepare multi-line files in a compact form.
 814
 815   Example:
 816
 817        test_write_lines a b c d e f g >foo
 818
 819   Is a more compact equivalent of:
 820        cat >foo <<-EOF
 821        a
 822        b
 823        c
 824        d
 825        e
 826        f
 827        g
 828        EOF
 829
 830
 831 - test_pause
 832
 833        This command is useful for writing and debugging tests and must be
 834        removed before submitting. It halts the execution of the test and
 835        spawns a shell in the trash directory. Exit the shell to continue
 836        the test. Example:
 837
 838        test_expect_success 'test' '
 839                git do-something >actual &&
 840                test_pause &&
 841                test_cmp expected actual
 842        '
 843
 844 - test_ln_s_add <path1> <path2>
 845
 846   This function helps systems whose filesystem does not support symbolic
 847   links. Use it to add a symbolic link entry to the index when it is not
 848   important that the file system entry is a symbolic link, i.e., instead
 849   of the sequence
 850
 851        ln -s foo bar &&
 852        git add bar
 853
 854   Sometimes it is possible to split a test in a part that does not need
 855   the symbolic link in the file system and a part that does; then only
 856   the latter part need be protected by a SYMLINKS prerequisite (see below).
 857
 858 - test_oid_init
 859
 860   This function loads facts and useful object IDs related to the hash
 861   algorithm(s) in use from the files in t/oid-info.
 862
 863 - test_oid_cache
 864
 865   This function reads per-hash algorithm information from standard
 866   input (usually a heredoc) in the format described in
 867   t/oid-info/README.  This is useful for test-specific values, such as
 868   object IDs, which must vary based on the hash algorithm.
 869
 870   Certain fixed values, such as hash sizes and common placeholder
 871   object IDs, can be loaded with test_oid_init (described above).
 872
 873 - test_oid <key>
 874
 875   This function looks up a value for the hash algorithm in use, based
 876   on the key given.  The value must have been loaded using
 877   test_oid_init or test_oid_cache.  Providing an unknown key is an
 878   error.
 879
 880Prerequisites
 881-------------
 882
 883These are the prerequisites that the test library predefines with
 884test_have_prereq.
 885
 886See the prereq argument to the test_* functions in the "Test harness
 887library" section above and the "test_have_prereq" function for how to
 888use these, and "test_set_prereq" for how to define your own.
 889
 890 - PYTHON
 891
 892   Git wasn't compiled with NO_PYTHON=YesPlease. Wrap any tests that
 893   need Python with this.
 894
 895 - PERL
 896
 897   Git wasn't compiled with NO_PERL=YesPlease.
 898
 899   Even without the PERL prerequisite, tests can assume there is a
 900   usable perl interpreter at $PERL_PATH, though it need not be
 901   particularly modern.
 902
 903 - POSIXPERM
 904
 905   The filesystem supports POSIX style permission bits.
 906
 907 - BSLASHPSPEC
 908
 909   Backslashes in pathspec are not directory separators. This is not
 910   set on Windows. See 6fd1106a for details.
 911
 912 - EXECKEEPSPID
 913
 914   The process retains the same pid across exec(2). See fb9a2bea for
 915   details.
 916
 917 - PIPE
 918
 919   The filesystem we're on supports creation of FIFOs (named pipes)
 920   via mkfifo(1).
 921
 922 - SYMLINKS
 923
 924   The filesystem we're on supports symbolic links. E.g. a FAT
 925   filesystem doesn't support these. See 704a3143 for details.
 926
 927 - SANITY
 928
 929   Test is not run by root user, and an attempt to write to an
 930   unwritable file is expected to fail correctly.
 931
 932 - PCRE
 933
 934   Git was compiled with support for PCRE. Wrap any tests
 935   that use git-grep --perl-regexp or git-grep -P in these.
 936
 937 - LIBPCRE1
 938
 939   Git was compiled with PCRE v1 support via
 940   USE_LIBPCRE1=YesPlease. Wrap any PCRE using tests that for some
 941   reason need v1 of the PCRE library instead of v2 in these.
 942
 943 - LIBPCRE2
 944
 945   Git was compiled with PCRE v2 support via
 946   USE_LIBPCRE2=YesPlease. Wrap any PCRE using tests that for some
 947   reason need v2 of the PCRE library instead of v1 in these.
 948
 949 - CASE_INSENSITIVE_FS
 950
 951   Test is run on a case insensitive file system.
 952
 953 - UTF8_NFD_TO_NFC
 954
 955   Test is run on a filesystem which converts decomposed utf-8 (nfd)
 956   to precomposed utf-8 (nfc).
 957
 958 - PTHREADS
 959
 960   Git wasn't compiled with NO_PTHREADS=YesPlease.
 961
 962Tips for Writing Tests
 963----------------------
 964
 965As with any programming projects, existing programs are the best
 966source of the information.  However, do _not_ emulate
 967t0000-basic.sh when writing your tests.  The test is special in
 968that it tries to validate the very core of GIT.  For example, it
 969knows that there will be 256 subdirectories under .git/objects/,
 970and it knows that the object ID of an empty tree is a certain
 97140-byte string.  This is deliberately done so in t0000-basic.sh
 972because the things the very basic core test tries to achieve is
 973to serve as a basis for people who are changing the GIT internal
 974drastically.  For these people, after making certain changes,
 975not seeing failures from the basic test _is_ a failure.  And
 976such drastic changes to the core GIT that even changes these
 977otherwise supposedly stable object IDs should be accompanied by
 978an update to t0000-basic.sh.
 979
 980However, other tests that simply rely on basic parts of the core
 981GIT working properly should not have that level of intimate
 982knowledge of the core GIT internals.  If all the test scripts
 983hardcoded the object IDs like t0000-basic.sh does, that defeats
 984the purpose of t0000-basic.sh, which is to isolate that level of
 985validation in one place.  Your test also ends up needing
 986updating when such a change to the internal happens, so do _not_
 987do it and leave the low level of validation to t0000-basic.sh.
 988
 989Test coverage
 990-------------
 991
 992You can use the coverage tests to find code paths that are not being
 993used or properly exercised yet.
 994
 995To do that, run the coverage target at the top-level (not in the t/
 996directory):
 997
 998    make coverage
 999
1000That'll compile Git with GCC's coverage arguments, and generate a test
1001report with gcov after the tests finish. Running the coverage tests
1002can take a while, since running the tests in parallel is incompatible
1003with GCC's coverage mode.
1004
1005After the tests have run you can generate a list of untested
1006functions:
1007
1008    make coverage-untested-functions
1009
1010You can also generate a detailed per-file HTML report using the
1011Devel::Cover module. To install it do:
1012
1013   # On Debian or Ubuntu:
1014   sudo aptitude install libdevel-cover-perl
1015
1016   # From the CPAN with cpanminus
1017   curl -L http://cpanmin.us | perl - --sudo --self-upgrade
1018   cpanm --sudo Devel::Cover
1019
1020Then, at the top-level:
1021
1022    make cover_db_html
1023
1024That'll generate a detailed cover report in the "cover_db_html"
1025directory, which you can then copy to a webserver, or inspect locally
1026in a browser.