t / READMEon commit t6036: avoid non-portable "cp -a" (cc4cb09)
   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 uncomon 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
 330Naming Tests
 331------------
 332
 333The test files are named as:
 334
 335        tNNNN-commandname-details.sh
 336
 337where N is a decimal digit.
 338
 339First digit tells the family:
 340
 341        0 - the absolute basics and global stuff
 342        1 - the basic commands concerning database
 343        2 - the basic commands concerning the working tree
 344        3 - the other basic commands (e.g. ls-files)
 345        4 - the diff commands
 346        5 - the pull and exporting commands
 347        6 - the revision tree commands (even e.g. merge-base)
 348        7 - the porcelainish commands concerning the working tree
 349        8 - the porcelainish commands concerning forensics
 350        9 - the git tools
 351
 352Second digit tells the particular command we are testing.
 353
 354Third digit (optionally) tells the particular switch or group of switches
 355we are testing.
 356
 357If you create files under t/ directory (i.e. here) that is not
 358the top-level test script, never name the file to match the above
 359pattern.  The Makefile here considers all such files as the
 360top-level test script and tries to run all of them.  Care is
 361especially needed if you are creating a common test library
 362file, similar to test-lib.sh, because such a library file may
 363not be suitable for standalone execution.
 364
 365
 366Writing Tests
 367-------------
 368
 369The test script is written as a shell script.  It should start
 370with the standard "#!/bin/sh", and an
 371assignment to variable 'test_description', like this:
 372
 373        #!/bin/sh
 374
 375        test_description='xxx test (option --frotz)
 376
 377        This test registers the following structure in the cache
 378        and tries to run git-ls-files with option --frotz.'
 379
 380
 381Source 'test-lib.sh'
 382--------------------
 383
 384After assigning test_description, the test script should source
 385test-lib.sh like this:
 386
 387        . ./test-lib.sh
 388
 389This test harness library does the following things:
 390
 391 - If the script is invoked with command line argument --help
 392   (or -h), it shows the test_description and exits.
 393
 394 - Creates an empty test directory with an empty .git/objects database
 395   and chdir(2) into it.  This directory is 't/trash
 396   directory.$test_name_without_dotsh', with t/ subject to change by
 397   the --root option documented above.
 398
 399 - Defines standard test helper functions for your scripts to
 400   use.  These functions are designed to make all scripts behave
 401   consistently when command line arguments --verbose (or -v),
 402   --debug (or -d), and --immediate (or -i) is given.
 403
 404Do's, don'ts & things to keep in mind
 405-------------------------------------
 406
 407Here are a few examples of things you probably should and shouldn't do
 408when writing tests.
 409
 410Do:
 411
 412 - Put all code inside test_expect_success and other assertions.
 413
 414   Even code that isn't a test per se, but merely some setup code
 415   should be inside a test assertion.
 416
 417 - Chain your test assertions
 418
 419   Write test code like this:
 420
 421        git merge foo &&
 422        git push bar &&
 423        test ...
 424
 425   Instead of:
 426
 427        git merge hla
 428        git push gh
 429        test ...
 430
 431   That way all of the commands in your tests will succeed or fail. If
 432   you must ignore the return value of something, consider using a
 433   helper function (e.g. use sane_unset instead of unset, in order
 434   to avoid unportable return value for unsetting a variable that was
 435   already unset), or prepending the command with test_might_fail or
 436   test_must_fail.
 437
 438 - Check the test coverage for your tests. See the "Test coverage"
 439   below.
 440
 441   Don't blindly follow test coverage metrics; if a new function you added
 442   doesn't have any coverage, then you're probably doing something wrong,
 443   but having 100% coverage doesn't necessarily mean that you tested
 444   everything.
 445
 446   Tests that are likely to smoke out future regressions are better
 447   than tests that just inflate the coverage metrics.
 448
 449 - When a test checks for an absolute path that a git command generated,
 450   construct the expected value using $(pwd) rather than $PWD,
 451   $TEST_DIRECTORY, or $TRASH_DIRECTORY. It makes a difference on
 452   Windows, where the shell (MSYS bash) mangles absolute path names.
 453   For details, see the commit message of 4114156ae9.
 454
 455Don't:
 456
 457 - exit() within a <script> part.
 458
 459   The harness will catch this as a programming error of the test.
 460   Use test_done instead if you need to stop the tests early (see
 461   "Skipping tests" below).
 462
 463 - use '! git cmd' when you want to make sure the git command exits
 464   with failure in a controlled way by calling "die()".  Instead,
 465   use 'test_must_fail git cmd'.  This will signal a failure if git
 466   dies in an unexpected way (e.g. segfault).
 467
 468   On the other hand, don't use test_must_fail for running regular
 469   platform commands; just use '! cmd'.  We are not in the business
 470   of verifying that the world given to us sanely works.
 471
 472 - use perl without spelling it as "$PERL_PATH". This is to help our
 473   friends on Windows where the platform Perl often adds CR before
 474   the end of line, and they bundle Git with a version of Perl that
 475   does not do so, whose path is specified with $PERL_PATH. Note that we
 476   provide a "perl" function which uses $PERL_PATH under the hood, so
 477   you do not need to worry when simply running perl in the test scripts
 478   (but you do, for example, on a shebang line or in a sub script
 479   created via "write_script").
 480
 481 - use sh without spelling it as "$SHELL_PATH", when the script can
 482   be misinterpreted by broken platform shell (e.g. Solaris).
 483
 484 - chdir around in tests.  It is not sufficient to chdir to
 485   somewhere and then chdir back to the original location later in
 486   the test, as any intermediate step can fail and abort the test,
 487   causing the next test to start in an unexpected directory.  Do so
 488   inside a subshell if necessary.
 489
 490 - save and verify the standard error of compound commands, i.e. group
 491   commands, subshells, and shell functions (except test helper
 492   functions like 'test_must_fail') like this:
 493
 494     ( cd dir && git cmd ) 2>error &&
 495     test_cmp expect error
 496
 497   When running the test with '-x' tracing, then the trace of commands
 498   executed in the compound command will be included in standard error
 499   as well, quite possibly throwing off the subsequent checks examining
 500   the output.  Instead, save only the relevant git command's standard
 501   error:
 502
 503     ( cd dir && git cmd 2>../error ) &&
 504     test_cmp expect error
 505
 506 - Break the TAP output
 507
 508   The raw output from your test may be interpreted by a TAP harness. TAP
 509   harnesses will ignore everything they don't know about, but don't step
 510   on their toes in these areas:
 511
 512   - Don't print lines like "$x..$y" where $x and $y are integers.
 513
 514   - Don't print lines that begin with "ok" or "not ok".
 515
 516   TAP harnesses expect a line that begins with either "ok" and "not
 517   ok" to signal a test passed or failed (and our harness already
 518   produces such lines), so your script shouldn't emit such lines to
 519   their output.
 520
 521   You can glean some further possible issues from the TAP grammar
 522   (see https://metacpan.org/pod/TAP::Parser::Grammar#TAP-GRAMMAR)
 523   but the best indication is to just run the tests with prove(1),
 524   it'll complain if anything is amiss.
 525
 526Keep in mind:
 527
 528 - Inside the <script> part, the standard output and standard error
 529   streams are discarded, and the test harness only reports "ok" or
 530   "not ok" to the end user running the tests. Under --verbose, they
 531   are shown to help debugging the tests.
 532
 533
 534Skipping tests
 535--------------
 536
 537If you need to skip tests you should do so by using the three-arg form
 538of the test_* functions (see the "Test harness library" section
 539below), e.g.:
 540
 541    test_expect_success PERL 'I need Perl' '
 542        perl -e "hlagh() if unf_unf()"
 543    '
 544
 545The advantage of skipping tests like this is that platforms that don't
 546have the PERL and other optional dependencies get an indication of how
 547many tests they're missing.
 548
 549If the test code is too hairy for that (i.e. does a lot of setup work
 550outside test assertions) you can also skip all remaining tests by
 551setting skip_all and immediately call test_done:
 552
 553        if ! test_have_prereq PERL
 554        then
 555            skip_all='skipping perl interface tests, perl not available'
 556            test_done
 557        fi
 558
 559The string you give to skip_all will be used as an explanation for why
 560the test was skipped.
 561
 562End with test_done
 563------------------
 564
 565Your script will be a sequence of tests, using helper functions
 566from the test harness library.  At the end of the script, call
 567'test_done'.
 568
 569
 570Test harness library
 571--------------------
 572
 573There are a handful helper functions defined in the test harness
 574library for your script to use.
 575
 576 - test_expect_success [<prereq>] <message> <script>
 577
 578   Usually takes two strings as parameters, and evaluates the
 579   <script>.  If it yields success, test is considered
 580   successful.  <message> should state what it is testing.
 581
 582   Example:
 583
 584        test_expect_success \
 585            'git-write-tree should be able to write an empty tree.' \
 586            'tree=$(git-write-tree)'
 587
 588   If you supply three parameters the first will be taken to be a
 589   prerequisite; see the test_set_prereq and test_have_prereq
 590   documentation below:
 591
 592        test_expect_success TTY 'git --paginate rev-list uses a pager' \
 593            ' ... '
 594
 595   You can also supply a comma-separated list of prerequisites, in the
 596   rare case where your test depends on more than one:
 597
 598        test_expect_success PERL,PYTHON 'yo dawg' \
 599            ' test $(perl -E 'print eval "1 +" . qx[python -c "print 2"]') == "4" '
 600
 601 - test_expect_failure [<prereq>] <message> <script>
 602
 603   This is NOT the opposite of test_expect_success, but is used
 604   to mark a test that demonstrates a known breakage.  Unlike
 605   the usual test_expect_success tests, which say "ok" on
 606   success and "FAIL" on failure, this will say "FIXED" on
 607   success and "still broken" on failure.  Failures from these
 608   tests won't cause -i (immediate) to stop.
 609
 610   Like test_expect_success this function can optionally use a three
 611   argument invocation with a prerequisite as the first argument.
 612
 613 - test_debug <script>
 614
 615   This takes a single argument, <script>, and evaluates it only
 616   when the test script is started with --debug command line
 617   argument.  This is primarily meant for use during the
 618   development of a new test script.
 619
 620 - debug <git-command>
 621
 622   Run a git command inside a debugger. This is primarily meant for
 623   use when debugging a failing test script.
 624
 625 - test_done
 626
 627   Your test script must have test_done at the end.  Its purpose
 628   is to summarize successes and failures in the test script and
 629   exit with an appropriate error code.
 630
 631 - test_tick
 632
 633   Make commit and tag names consistent by setting the author and
 634   committer times to defined state.  Subsequent calls will
 635   advance the times by a fixed amount.
 636
 637 - test_commit <message> [<filename> [<contents>]]
 638
 639   Creates a commit with the given message, committing the given
 640   file with the given contents (default for both is to reuse the
 641   message string), and adds a tag (again reusing the message
 642   string as name).  Calls test_tick to make the SHA-1s
 643   reproducible.
 644
 645 - test_merge <message> <commit-or-tag>
 646
 647   Merges the given rev using the given message.  Like test_commit,
 648   creates a tag and calls test_tick before committing.
 649
 650 - test_set_prereq <prereq>
 651
 652   Set a test prerequisite to be used later with test_have_prereq. The
 653   test-lib will set some prerequisites for you, see the
 654   "Prerequisites" section below for a full list of these.
 655
 656   Others you can set yourself and use later with either
 657   test_have_prereq directly, or the three argument invocation of
 658   test_expect_success and test_expect_failure.
 659
 660 - test_have_prereq <prereq>
 661
 662   Check if we have a prerequisite previously set with test_set_prereq.
 663   The most common way to use this explicitly (as opposed to the
 664   implicit use when an argument is passed to test_expect_*) is to skip
 665   all the tests at the start of the test script if we don't have some
 666   essential prerequisite:
 667
 668        if ! test_have_prereq PERL
 669        then
 670            skip_all='skipping perl interface tests, perl not available'
 671            test_done
 672        fi
 673
 674 - test_external [<prereq>] <message> <external> <script>
 675
 676   Execute a <script> with an <external> interpreter (like perl). This
 677   was added for tests like t9700-perl-git.sh which do most of their
 678   work in an external test script.
 679
 680        test_external \
 681            'GitwebCache::*FileCache*' \
 682            perl "$TEST_DIRECTORY"/t9503/test_cache_interface.pl
 683
 684   If the test is outputting its own TAP you should set the
 685   test_external_has_tap variable somewhere before calling the first
 686   test_external* function. See t9700-perl-git.sh for an example.
 687
 688        # The external test will outputs its own plan
 689        test_external_has_tap=1
 690
 691 - test_external_without_stderr [<prereq>] <message> <external> <script>
 692
 693   Like test_external but fail if there's any output on stderr,
 694   instead of checking the exit code.
 695
 696        test_external_without_stderr \
 697            'Perl API' \
 698            perl "$TEST_DIRECTORY"/t9700/test.pl
 699
 700 - test_expect_code <exit-code> <command>
 701
 702   Run a command and ensure that it exits with the given exit code.
 703   For example:
 704
 705        test_expect_success 'Merge with d/f conflicts' '
 706                test_expect_code 1 git merge "merge msg" B master
 707        '
 708
 709 - test_must_fail [<options>] <git-command>
 710
 711   Run a git command and ensure it fails in a controlled way.  Use
 712   this instead of "! <git-command>".  When git-command dies due to a
 713   segfault, test_must_fail diagnoses it as an error; "! <git-command>"
 714   treats it as just another expected failure, which would let such a
 715   bug go unnoticed.
 716
 717   Accepts the following options:
 718
 719     ok=<signal-name>[,<...>]:
 720       Don't treat an exit caused by the given signal as error.
 721       Multiple signals can be specified as a comma separated list.
 722       Currently recognized signal names are: sigpipe, success.
 723       (Don't use 'success', use 'test_might_fail' instead.)
 724
 725 - test_might_fail [<options>] <git-command>
 726
 727   Similar to test_must_fail, but tolerate success, too.  Use this
 728   instead of "<git-command> || :" to catch failures due to segv.
 729
 730   Accepts the same options as test_must_fail.
 731
 732 - test_cmp <expected> <actual>
 733
 734   Check whether the content of the <actual> file matches the
 735   <expected> file.  This behaves like "cmp" but produces more
 736   helpful output when the test is run with "-v" option.
 737
 738 - test_cmp_rev <expected> <actual>
 739
 740   Check whether the <expected> rev points to the same commit as the
 741   <actual> rev.
 742
 743 - test_line_count (= | -lt | -ge | ...) <length> <file>
 744
 745   Check whether a file has the length it is expected to.
 746
 747 - test_path_is_file <path> [<diagnosis>]
 748   test_path_is_dir <path> [<diagnosis>]
 749   test_path_is_missing <path> [<diagnosis>]
 750
 751   Check if the named path is a file, if the named path is a
 752   directory, or if the named path does not exist, respectively,
 753   and fail otherwise, showing the <diagnosis> text.
 754
 755 - test_when_finished <script>
 756
 757   Prepend <script> to a list of commands to run to clean up
 758   at the end of the current test.  If some clean-up command
 759   fails, the test will not pass.
 760
 761   Example:
 762
 763        test_expect_success 'branch pointing to non-commit' '
 764                git rev-parse HEAD^{tree} >.git/refs/heads/invalid &&
 765                test_when_finished "git update-ref -d refs/heads/invalid" &&
 766                ...
 767        '
 768
 769 - test_write_lines <lines>
 770
 771   Write <lines> on standard output, one line per argument.
 772   Useful to prepare multi-line files in a compact form.
 773
 774   Example:
 775
 776        test_write_lines a b c d e f g >foo
 777
 778   Is a more compact equivalent of:
 779        cat >foo <<-EOF
 780        a
 781        b
 782        c
 783        d
 784        e
 785        f
 786        g
 787        EOF
 788
 789
 790 - test_pause
 791
 792        This command is useful for writing and debugging tests and must be
 793        removed before submitting. It halts the execution of the test and
 794        spawns a shell in the trash directory. Exit the shell to continue
 795        the test. Example:
 796
 797        test_expect_success 'test' '
 798                git do-something >actual &&
 799                test_pause &&
 800                test_cmp expected actual
 801        '
 802
 803 - test_ln_s_add <path1> <path2>
 804
 805   This function helps systems whose filesystem does not support symbolic
 806   links. Use it to add a symbolic link entry to the index when it is not
 807   important that the file system entry is a symbolic link, i.e., instead
 808   of the sequence
 809
 810        ln -s foo bar &&
 811        git add bar
 812
 813   Sometimes it is possible to split a test in a part that does not need
 814   the symbolic link in the file system and a part that does; then only
 815   the latter part need be protected by a SYMLINKS prerequisite (see below).
 816
 817Prerequisites
 818-------------
 819
 820These are the prerequisites that the test library predefines with
 821test_have_prereq.
 822
 823See the prereq argument to the test_* functions in the "Test harness
 824library" section above and the "test_have_prereq" function for how to
 825use these, and "test_set_prereq" for how to define your own.
 826
 827 - PYTHON
 828
 829   Git wasn't compiled with NO_PYTHON=YesPlease. Wrap any tests that
 830   need Python with this.
 831
 832 - PERL
 833
 834   Git wasn't compiled with NO_PERL=YesPlease.
 835
 836   Even without the PERL prerequisite, tests can assume there is a
 837   usable perl interpreter at $PERL_PATH, though it need not be
 838   particularly modern.
 839
 840 - POSIXPERM
 841
 842   The filesystem supports POSIX style permission bits.
 843
 844 - BSLASHPSPEC
 845
 846   Backslashes in pathspec are not directory separators. This is not
 847   set on Windows. See 6fd1106a for details.
 848
 849 - EXECKEEPSPID
 850
 851   The process retains the same pid across exec(2). See fb9a2bea for
 852   details.
 853
 854 - PIPE
 855
 856   The filesystem we're on supports creation of FIFOs (named pipes)
 857   via mkfifo(1).
 858
 859 - SYMLINKS
 860
 861   The filesystem we're on supports symbolic links. E.g. a FAT
 862   filesystem doesn't support these. See 704a3143 for details.
 863
 864 - SANITY
 865
 866   Test is not run by root user, and an attempt to write to an
 867   unwritable file is expected to fail correctly.
 868
 869 - PCRE
 870
 871   Git was compiled with support for PCRE. Wrap any tests
 872   that use git-grep --perl-regexp or git-grep -P in these.
 873
 874 - LIBPCRE1
 875
 876   Git was compiled with PCRE v1 support via
 877   USE_LIBPCRE1=YesPlease. Wrap any PCRE using tests that for some
 878   reason need v1 of the PCRE library instead of v2 in these.
 879
 880 - LIBPCRE2
 881
 882   Git was compiled with PCRE v2 support via
 883   USE_LIBPCRE2=YesPlease. Wrap any PCRE using tests that for some
 884   reason need v2 of the PCRE library instead of v1 in these.
 885
 886 - CASE_INSENSITIVE_FS
 887
 888   Test is run on a case insensitive file system.
 889
 890 - UTF8_NFD_TO_NFC
 891
 892   Test is run on a filesystem which converts decomposed utf-8 (nfd)
 893   to precomposed utf-8 (nfc).
 894
 895 - PTHREADS
 896
 897   Git wasn't compiled with NO_PTHREADS=YesPlease.
 898
 899Tips for Writing Tests
 900----------------------
 901
 902As with any programming projects, existing programs are the best
 903source of the information.  However, do _not_ emulate
 904t0000-basic.sh when writing your tests.  The test is special in
 905that it tries to validate the very core of GIT.  For example, it
 906knows that there will be 256 subdirectories under .git/objects/,
 907and it knows that the object ID of an empty tree is a certain
 90840-byte string.  This is deliberately done so in t0000-basic.sh
 909because the things the very basic core test tries to achieve is
 910to serve as a basis for people who are changing the GIT internal
 911drastically.  For these people, after making certain changes,
 912not seeing failures from the basic test _is_ a failure.  And
 913such drastic changes to the core GIT that even changes these
 914otherwise supposedly stable object IDs should be accompanied by
 915an update to t0000-basic.sh.
 916
 917However, other tests that simply rely on basic parts of the core
 918GIT working properly should not have that level of intimate
 919knowledge of the core GIT internals.  If all the test scripts
 920hardcoded the object IDs like t0000-basic.sh does, that defeats
 921the purpose of t0000-basic.sh, which is to isolate that level of
 922validation in one place.  Your test also ends up needing
 923updating when such a change to the internal happens, so do _not_
 924do it and leave the low level of validation to t0000-basic.sh.
 925
 926Test coverage
 927-------------
 928
 929You can use the coverage tests to find code paths that are not being
 930used or properly exercised yet.
 931
 932To do that, run the coverage target at the top-level (not in the t/
 933directory):
 934
 935    make coverage
 936
 937That'll compile Git with GCC's coverage arguments, and generate a test
 938report with gcov after the tests finish. Running the coverage tests
 939can take a while, since running the tests in parallel is incompatible
 940with GCC's coverage mode.
 941
 942After the tests have run you can generate a list of untested
 943functions:
 944
 945    make coverage-untested-functions
 946
 947You can also generate a detailed per-file HTML report using the
 948Devel::Cover module. To install it do:
 949
 950   # On Debian or Ubuntu:
 951   sudo aptitude install libdevel-cover-perl
 952
 953   # From the CPAN with cpanminus
 954   curl -L http://cpanmin.us | perl - --sudo --self-upgrade
 955   cpanm --sudo Devel::Cover
 956
 957Then, at the top-level:
 958
 959    make cover_db_html
 960
 961That'll generate a detailed cover report in the "cover_db_html"
 962directory, which you can then copy to a webserver, or inspect locally
 963in a browser.