Test for generated patchname with trailing period

[stgit.git] / t / README

The mechanism that powers this testsuite is directly imported from the
Core Git Tests, in directory t/ of the git repository.  Files are base
on git version 2.20.0.

Core Git Tests
==============

This directory holds many test scripts for core Git tools.  The
first part of this short document describes how to run the tests
and read their output.

When fixing the tools or adding enhancements, you are strongly
encouraged to add tests in this directory to cover what you are
trying to fix or enhance.  The later part of this short document
describes how your test scripts should be organized.


Running Tests
-------------

The easiest way to run tests is to say "make".  This runs all
the tests.

    *** t0000-basic.sh ***
    ok 1 - .git/objects should be empty after git init in an empty repo.
    ok 2 - .git/objects should have 3 subdirectories.
    ok 3 - success is reported like this
    ...
    ok 43 - very long name in the index handled sanely
    # fixed 1 known breakage(s)
    # still have 1 known breakage(s)
    # passed all remaining 42 test(s)
    1..43
    *** t0001-init.sh ***
    ok 1 - plain
    ok 2 - plain with GIT_WORK_TREE
    ok 3 - plain bare

Since the tests all output TAP (see http://testanything.org) they can
be run with any TAP harness. Here's an example of parallel testing
powered by a recent version of prove(1):

    $ prove --timer --jobs 15 ./t[0-9]*.sh
    [19:17:33] ./t0005-signals.sh ................................... ok       36 ms
    [19:17:33] ./t0022-crlf-rename.sh ............................... ok       69 ms
    [19:17:33] ./t0024-crlf-archive.sh .............................. ok      154 ms
    [19:17:33] ./t0004-unwritable.sh ................................ ok      289 ms
    [19:17:33] ./t0002-gitfile.sh ................................... ok      480 ms
    ===(     102;0  25/?  6/?  5/?  16/?  1/?  4/?  2/?  1/?  3/?  1... )===

prove and other harnesses come with a lot of useful options. The
--state option in particular is very useful:

    # Repeat until no more failures
    $ prove -j 15 --state=failed,save ./t[0-9]*.sh

You can give DEFAULT_TEST_TARGET=prove on the make command (or define it
in config.mak) to cause "make test" to run tests under prove.
STG_PROVE_OPTS can be used to pass additional options, e.g.

    $ make DEFAULT_TEST_TARGET=prove STG_PROVE_OPTS='--timer --jobs 16' test

You can also run each test individually from command line, like this:

    $ sh ./t3010-ls-files-killed-modified.sh
    ok 1 - git update-index --add to add various paths.
    ok 2 - git ls-files -k to show killed files.
    ok 3 - validate git ls-files -k output.
    ok 4 - git ls-files -m to show modified files.
    ok 5 - validate git ls-files -m output.
    # passed all 5 test(s)
    1..5

You can pass --verbose (or -v), --debug (or -d), and --immediate
(or -i) command line argument to the test, or by setting STG_TEST_OPTS
appropriately before running "make".

-v::
--verbose::
        This makes the test more verbose.  Specifically, the
        command being run and their output if any are also
        output.

--verbose-only=<pattern>::
        Like --verbose, but the effect is limited to tests with
        numbers matching <pattern>.  The number matched against is
        simply the running count of the test within the file.

-x::
        Turn on shell tracing (i.e., `set -x`) during the tests
        themselves. Implies `--verbose`.
        Ignored in test scripts that set the variable 'test_untraceable'
        to a non-empty value, unless it's run with a Bash version
        supporting BASH_XTRACEFD, i.e. v4.1 or later.

-d::
--debug::
        This may help the person who is developing a new test.
        It causes the command defined with test_debug to run.
        The "trash" directory (used to store all temporary data
        during testing) is not deleted even if there are no
        failed tests so that you can inspect its contents after
        the test finished.

-i::
--immediate::
        This causes the test to immediately exit upon the first
        failed test. Cleanup commands requested with
        test_when_finished are not executed if the test failed,
        in order to keep the state for inspection by the tester
        to diagnose the bug.

-l::
--long-tests::
        This causes additional long-running tests to be run (where
        available), for more exhaustive testing.

-r::
--run=<test-selector>::
        Run only the subset of tests indicated by
        <test-selector>.  See section "Skipping Tests" below for
        <test-selector> syntax.

--tee::
        In addition to printing the test output to the terminal,
        write it to files named 't/test-results/$TEST_NAME.out'.
        As the names depend on the tests' file names, it is safe to
        run the tests with this option in parallel.

-V::
--verbose-log::
        Write verbose output to the same logfile as `--tee`, but do
        _not_ write it to stdout. Unlike `--tee --verbose`, this option
        is safe to use when stdout is being consumed by a TAP parser
        like `prove`. Implies `--tee` and `--verbose`.

--root=<directory>::
        Create "trash" directories used to store all temporary data during
        testing under <directory>, instead of the t/ directory.
        Using this option with a RAM-based filesystem (such as tmpfs)
        can massively speed up the test suite.

--stress-jobs=<N>::
        Override the number of parallel jobs. Implies `--stress`.

--stress-limit=<N>::
        When combined with --stress run the test script repeatedly
        this many times in each of the parallel jobs or until one of
        them fails, whichever comes first. Implies `--stress`.

You can also set the STG_TEST_INSTALLED environment variable to
the bindir of an existing git installation to test that installation.
You still need to have built this git sandbox, from which various
test-* support programs, templates, and perl libraries are used.
If your installed git is incomplete, it will silently test parts of
your built version instead.


Skipping Tests
--------------

In some environments, certain tests have no way of succeeding
due to platform limitation, such as lack of 'unzip' program, or
filesystem that do not allow arbitrary sequence of non-NUL bytes
as pathnames.

You should be able to say something like

    $ STG_SKIP_TESTS=t9200.8 sh ./t9200-git-cvsexport-commit.sh

and even:

    $ STG_SKIP_TESTS='t[0-4]??? t91?? t9200.8' make

to omit such tests.  The value of the environment variable is a
SP separated list of patterns that tells which tests to skip,
and either can match the "t[0-9]{4}" part to skip the whole
test, or t[0-9]{4} followed by ".$number" to say which
particular test to skip.

For an individual test suite --run could be used to specify that
only some tests should be run or that some tests should be
excluded from a run.

The argument for --run is a list of individual test numbers or
ranges with an optional negation prefix that define what tests in
a test suite to include in the run.  A range is two numbers
separated with a dash and matches a range of tests with both ends
been included.  You may omit the first or the second number to
mean "from the first test" or "up to the very last test"
respectively.

Optional prefix of '!' means that the test or a range of tests
should be excluded from the run.

If --run starts with an unprefixed number or range the initial
set of tests to run is empty. If the first item starts with '!'
all the tests are added to the initial set.  After initial set is
determined every test number or range is added or excluded from
the set one by one, from left to right.

Individual numbers or ranges could be separated either by a space
or a comma.

For example, to run only tests up to a specific test (21), one
could do this:

    $ sh ./t9200-git-cvsexport-commit.sh --run='1-21'

or this:

    $ sh ./t9200-git-cvsexport-commit.sh --run='-21'

Common case is to run several setup tests (1, 2, 3) and then a
specific test (21) that relies on that setup:

    $ sh ./t9200-git-cvsexport-commit.sh --run='1 2 3 21'

or:

    $ sh ./t9200-git-cvsexport-commit.sh --run=1,2,3,21

or:

    $ sh ./t9200-git-cvsexport-commit.sh --run='-3 21'

As noted above, the test set is built by going through the items
from left to right, so this:

    $ sh ./t9200-git-cvsexport-commit.sh --run='1-4 !3'

will run tests 1, 2, and 4.  Items that come later have higher
precedence.  It means that this:

    $ sh ./t9200-git-cvsexport-commit.sh --run='!3 1-4'

would just run tests from 1 to 4, including 3.

You may use negation with ranges.  The following will run all
test in the test suite except from 7 up to 11:

    $ sh ./t9200-git-cvsexport-commit.sh --run='!7-11'

Some tests in a test suite rely on the previous tests performing
certain actions, specifically some tests are designated as
"setup" test, so you cannot _arbitrarily_ disable one test and
expect the rest to function correctly.

--run is mostly useful when you want to focus on a specific test
and know what setup is needed for it.  Or when you want to run
everything up to a certain test.


Running tests with special setups
---------------------------------

The whole test suite could be run to test some special features
that cannot be easily covered by a few specific test cases. These
could be enabled by running the test suite with correct STG_TEST_
environment set.

PYTHON=<python executable> use alternative python executable to
run stg in tests. By default `python3` is used. Alternatives such
as `python3.7`may be specified. The build must have been previously
performed using this PYTHON variable. Some example uses:

    $ make PYTHON=python3.7 test
    $ make PYTHON=python3.6
    $ cd t/
    $ make PYTHON=python3.6 prove
    $ PYTHON=python3.7 ./t3300-edit.sh

STG_TEST_LANG=<encoding> use an encoding other than the default C
encoding. Affects LANG and LC_ALL environment variables.

GIT_TEST_INDEX_VERSION=<n> exercises the index read/write code path
for the index version specified.  Can be set to any valid version
(currently 2, 3, or 4).

Naming Tests
------------

The test files are named as:

        tNNNN-commandname-details.sh

where N is a decimal digit.

First digit tells the family:

        0 - the absolute basics and global stuff
        1 - the basic commands concerning database
        2 - the basic commands concerning the working tree
        3 - the other basic commands (e.g. ls-files)
        4 - the diff commands
        5 - the pull and exporting commands
        6 - the revision tree commands (even e.g. merge-base)
        7 - the porcelainish commands concerning the working tree
        8 - the porcelainish commands concerning forensics
        9 - the git tools

Second digit tells the particular command we are testing.

Third digit (optionally) tells the particular switch or group of switches
we are testing.

If you create files under t/ directory (i.e. here) that is not
the top-level test script, never name the file to match the above
pattern.  The Makefile here considers all such files as the
top-level test script and tries to run all of them.  Care is
especially needed if you are creating a common test library
file, similar to test-lib.sh, because such a library file may
not be suitable for standalone execution.


Writing Tests
-------------

The test script is written as a shell script.  It should start
with the standard "#!/bin/sh", and an
assignment to variable 'test_description', like this:

        #!/bin/sh

        test_description='xxx test (option --frotz)

        This test registers the following structure in the cache
        and tries to run git-ls-files with option --frotz.'


Source 'test-lib.sh'
--------------------

After assigning test_description, the test script should source
test-lib.sh like this:

        . ./test-lib.sh

This test harness library does the following things:

 - If the script is invoked with command line argument --help
   (or -h), it shows the test_description and exits.

 - Creates an empty test directory with an empty .git/objects database
   and chdir(2) into it.  This directory is 't/trash
   directory.$test_name_without_dotsh', with t/ subject to change by
   the --root option documented above, and a '.stress-<N>' suffix
   appended by the --stress option.

 - Defines standard test helper functions for your scripts to
   use.  These functions are designed to make all scripts behave
   consistently when command line arguments --verbose (or -v),
   --debug (or -d), and --immediate (or -i) is given.

Do's & don'ts
-------------

Here are a few examples of things you probably should and shouldn't do
when writing tests.

Here are the "do's:"

 - Put all code inside test_expect_success and other assertions.

   Even code that isn't a test per se, but merely some setup code
   should be inside a test assertion.

 - Chain your test assertions

   Write test code like this:

        git merge foo &&
        git push bar &&
        test ...

   Instead of:

        git merge hla
        git push gh
        test ...

   That way all of the commands in your tests will succeed or fail. If
   you must ignore the return value of something, consider using a
   helper function (e.g. use sane_unset instead of unset, in order
   to avoid unportable return value for unsetting a variable that was
   already unset), or prepending the command with test_might_fail or
   test_must_fail.

 - Check the test coverage for your tests. See the "Test coverage"
   below.

   Don't blindly follow test coverage metrics; if a new function you added
   doesn't have any coverage, then you're probably doing something wrong,
   but having 100% coverage doesn't necessarily mean that you tested
   everything.

   Tests that are likely to smoke out future regressions are better
   than tests that just inflate the coverage metrics.

 - When a test checks for an absolute path that a git command generated,
   construct the expected value using $(pwd) rather than $PWD,
   $TEST_DIRECTORY, or $TRASH_DIRECTORY. It makes a difference on
   Windows, where the shell (MSYS bash) mangles absolute path names.
   For details, see the commit message of 4114156ae9.

 - Remember that inside the <script> part, the standard output and
   standard error streams are discarded, and the test harness only
   reports "ok" or "not ok" to the end user running the tests. Under
   --verbose, they are shown to help debug the tests.

And here are the "don'ts:"

 - Don't exit() within a <script> part.

   The harness will catch this as a programming error of the test.
   Use test_done instead if you need to stop the tests early (see
   "Skipping tests" below).

 - Don't use '! git cmd' when you want to make sure the git command
   exits with failure in a controlled way by calling "die()".  Instead,
   use 'test_must_fail git cmd'.  This will signal a failure if git
   dies in an unexpected way (e.g. segfault).

   On the other hand, don't use test_must_fail for running regular
   platform commands; just use '! cmd'.  We are not in the business
   of verifying that the world given to us sanely works.

 - Don't feed the output of a git command to a pipe, as in:

     git -C repo ls-files |
     xargs -n 1 basename |
     grep foo

   which will discard git's exit code and may mask a crash. In the
   above example, all exit codes are ignored except grep's.

   Instead, write the output of that command to a temporary
   file with ">" or assign it to a variable with "x=$(git ...)" rather
   than pipe it.

 - Don't use command substitution in a way that discards git's exit
   code. When assigning to a variable, the exit code is not discarded,
   e.g.:

     x=$(git cat-file -p $sha) &&
     ...

   is OK because a crash in "git cat-file" will cause the "&&" chain
   to fail, but:

     test "refs/heads/foo" = "$(git symbolic-ref HEAD)"

   is not OK and a crash in git could go undetected.

 - Don't use perl without spelling it as "$PERL_PATH". This is to help
   our friends on Windows where the platform Perl often adds CR before
   the end of line, and they bundle Git with a version of Perl that
   does not do so, whose path is specified with $PERL_PATH. Note that we
   provide a "perl" function which uses $PERL_PATH under the hood, so
   you do not need to worry when simply running perl in the test scripts
   (but you do, for example, on a shebang line or in a sub script
   created via "write_script").

 - Don't use sh without spelling it as "$SHELL_PATH", when the script
   can be misinterpreted by broken platform shell (e.g. Solaris).

 - Don't chdir around in tests.  It is not sufficient to chdir to
   somewhere and then chdir back to the original location later in
   the test, as any intermediate step can fail and abort the test,
   causing the next test to start in an unexpected directory.  Do so
   inside a subshell if necessary.

 - Don't save and verify the standard error of compound commands, i.e.
   group commands, subshells, and shell functions (except test helper
   functions like 'test_must_fail') like this:

     ( cd dir && git cmd ) 2>error &&
     test_cmp expect error

   When running the test with '-x' tracing, then the trace of commands
   executed in the compound command will be included in standard error
   as well, quite possibly throwing off the subsequent checks examining
   the output.  Instead, save only the relevant git command's standard
   error:

     ( cd dir && git cmd 2>../error ) &&
     test_cmp expect error

 - Don't break the TAP output

   The raw output from your test may be interpreted by a TAP harness. TAP
   harnesses will ignore everything they don't know about, but don't step
   on their toes in these areas:

   - Don't print lines like "$x..$y" where $x and $y are integers.

   - Don't print lines that begin with "ok" or "not ok".

   TAP harnesses expect a line that begins with either "ok" and "not
   ok" to signal a test passed or failed (and our harness already
   produces such lines), so your script shouldn't emit such lines to
   their output.

   You can glean some further possible issues from the TAP grammar
   (see https://metacpan.org/pod/TAP::Parser::Grammar#TAP-GRAMMAR)
   but the best indication is to just run the tests with prove(1),
   it'll complain if anything is amiss.


Skipping tests
--------------

If you need to skip tests you should do so by using the three-arg form
of the test_* functions (see the "Test harness library" section
below), e.g.:

    test_expect_success PERL 'I need Perl' '
        perl -e "hlagh() if unf_unf()"
    '

The advantage of skipping tests like this is that platforms that don't
have the PERL and other optional dependencies get an indication of how
many tests they're missing.

If the test code is too hairy for that (i.e. does a lot of setup work
outside test assertions) you can also skip all remaining tests by
setting skip_all and immediately call test_done:

        if ! test_have_prereq PERL
        then
            skip_all='skipping perl interface tests, perl not available'
            test_done
        fi

The string you give to skip_all will be used as an explanation for why
the test was skipped.

End with test_done
------------------

Your script will be a sequence of tests, using helper functions
from the test harness library.  At the end of the script, call
'test_done'.


Test harness library
--------------------

There are a handful helper functions defined in the test harness
library for your script to use.

 - test_expect_success [<prereq>] <message> <script>

   Usually takes two strings as parameters, and evaluates the
   <script>.  If it yields success, test is considered
   successful.  <message> should state what it is testing.

   Example:

        test_expect_success \
            'git-write-tree should be able to write an empty tree.' \
            'tree=$(git-write-tree)'

   If you supply three parameters the first will be taken to be a
   prerequisite; see the test_set_prereq and test_have_prereq
   documentation below:

        test_expect_success TTY 'git --paginate rev-list uses a pager' \
            ' ... '

   You can also supply a comma-separated list of prerequisites, in the
   rare case where your test depends on more than one:

        test_expect_success PERL,PYTHON 'yo dawg' \
            ' test $(perl -E 'print eval "1 +" . qx[python -c "print 2"]') == "4" '

 - test_expect_failure [<prereq>] <message> <script>

   This is NOT the opposite of test_expect_success, but is used
   to mark a test that demonstrates a known breakage.  Unlike
   the usual test_expect_success tests, which say "ok" on
   success and "FAIL" on failure, this will say "FIXED" on
   success and "still broken" on failure.  Failures from these
   tests won't cause -i (immediate) to stop.

   Like test_expect_success this function can optionally use a three
   argument invocation with a prerequisite as the first argument.

 - test_debug <script>

   This takes a single argument, <script>, and evaluates it only
   when the test script is started with --debug command line
   argument.  This is primarily meant for use during the
   development of a new test script.

 - debug <git-command>

   Run a git command inside a debugger. This is primarily meant for
   use when debugging a failing test script.

 - test_done

   Your test script must have test_done at the end.  Its purpose
   is to summarize successes and failures in the test script and
   exit with an appropriate error code.

 - test_tick

   Make commit and tag names consistent by setting the author and
   committer times to defined state.  Subsequent calls will
   advance the times by a fixed amount.

 - test_commit <message> [<filename> [<contents>]]

   Creates a commit with the given message, committing the given
   file with the given contents (default for both is to reuse the
   message string), and adds a tag (again reusing the message
   string as name).  Calls test_tick to make the SHA-1s
   reproducible.

 - test_merge <message> <commit-or-tag>

   Merges the given rev using the given message.  Like test_commit,
   creates a tag and calls test_tick before committing.

 - test_set_prereq <prereq>

   Set a test prerequisite to be used later with test_have_prereq. The
   test-lib will set some prerequisites for you, see the
   "Prerequisites" section below for a full list of these.

   Others you can set yourself and use later with either
   test_have_prereq directly, or the three argument invocation of
   test_expect_success and test_expect_failure.

 - test_have_prereq <prereq>

   Check if we have a prerequisite previously set with test_set_prereq.
   The most common way to use this explicitly (as opposed to the
   implicit use when an argument is passed to test_expect_*) is to skip
   all the tests at the start of the test script if we don't have some
   essential prerequisite:

        if ! test_have_prereq PERL
        then
            skip_all='skipping perl interface tests, perl not available'
            test_done
        fi

 - test_external [<prereq>] <message> <external> <script>

   Execute a <script> with an <external> interpreter (like perl). This
   was added for tests like t9700-perl-git.sh which do most of their
   work in an external test script.

        test_external \
            'GitwebCache::*FileCache*' \
            perl "$TEST_DIRECTORY"/t9503/test_cache_interface.pl

   If the test is outputting its own TAP you should set the
   test_external_has_tap variable somewhere before calling the first
   test_external* function. See t9700-perl-git.sh for an example.

        # The external test will outputs its own plan
        test_external_has_tap=1

 - test_external_without_stderr [<prereq>] <message> <external> <script>

   Like test_external but fail if there's any output on stderr,
   instead of checking the exit code.

        test_external_without_stderr \
            'Perl API' \
            perl "$TEST_DIRECTORY"/t9700/test.pl

 - test_expect_code <exit-code> <command>

   Run a command and ensure that it exits with the given exit code.
   For example:

        test_expect_success 'Merge with d/f conflicts' '
                test_expect_code 1 git merge "merge msg" B master
        '

 - test_must_fail [<options>] <git-command>

   Run a git command and ensure it fails in a controlled way.  Use
   this instead of "! <git-command>".  When git-command dies due to a
   segfault, test_must_fail diagnoses it as an error; "! <git-command>"
   treats it as just another expected failure, which would let such a
   bug go unnoticed.

   Accepts the following options:

     ok=<signal-name>[,<...>]:
       Don't treat an exit caused by the given signal as error.
       Multiple signals can be specified as a comma separated list.
       Currently recognized signal names are: sigpipe, success.
       (Don't use 'success', use 'test_might_fail' instead.)

 - test_might_fail [<options>] <git-command>

   Similar to test_must_fail, but tolerate success, too.  Use this
   instead of "<git-command> || :" to catch failures due to segv.

   Accepts the same options as test_must_fail.

 - test_cmp <expected> <actual>

   Check whether the content of the <actual> file matches the
   <expected> file.  This behaves like "cmp" but produces more
   helpful output when the test is run with "-v" option.

 - test_cmp_rev <expected> <actual>

   Check whether the <expected> rev points to the same commit as the
   <actual> rev.

 - test_line_count (= | -lt | -ge | ...) <length> <file>

   Check whether a file has the length it is expected to.

 - test_path_is_file <path> [<diagnosis>]
   test_path_is_dir <path> [<diagnosis>]
   test_path_is_missing <path> [<diagnosis>]

   Check if the named path is a file, if the named path is a
   directory, or if the named path does not exist, respectively,
   and fail otherwise, showing the <diagnosis> text.

 - test_when_finished <script>

   Prepend <script> to a list of commands to run to clean up
   at the end of the current test.  If some clean-up command
   fails, the test will not pass.

   Example:

        test_expect_success 'branch pointing to non-commit' '
                git rev-parse HEAD^{tree} >.git/refs/heads/invalid &&
                test_when_finished "git update-ref -d refs/heads/invalid" &&
                ...
        '

 - test_atexit <script>

   Prepend <script> to a list of commands to run unconditionally to
   clean up before the test script exits, e.g. to stop a daemon:

        test_expect_success 'test git daemon' '
                git daemon &
                daemon_pid=$! &&
                test_atexit 'kill $daemon_pid' &&
                hello world
        '

   The commands will be executed before the trash directory is removed,
   i.e. the atexit commands will still be able to access any pidfiles or
   socket files.

   Note that these commands will be run even when a test script run
   with '--immediate' fails.  Be careful with your atexit commands to
   minimize any changes to the failed state.

 - test_write_lines <lines>

   Write <lines> on standard output, one line per argument.
   Useful to prepare multi-line files in a compact form.

   Example:

        test_write_lines a b c d e f g >foo

   Is a more compact equivalent of:
        cat >foo <<-EOF
        a
        b
        c
        d
        e
        f
        g
        EOF


 - test_pause

        This command is useful for writing and debugging tests and must be
        removed before submitting. It halts the execution of the test and
        spawns a shell in the trash directory. Exit the shell to continue
        the test. Example:

        test_expect_success 'test' '
                git do-something >actual &&
                test_pause &&
                test_cmp expected actual
        '

 - test_ln_s_add <path1> <path2>

   This function helps systems whose filesystem does not support symbolic
   links. Use it to add a symbolic link entry to the index when it is not
   important that the file system entry is a symbolic link, i.e., instead
   of the sequence

        ln -s foo bar &&
        git add bar

   Sometimes it is possible to split a test in a part that does not need
   the symbolic link in the file system and a part that does; then only
   the latter part need be protected by a SYMLINKS prerequisite (see below).

 - test_oid_init

   This function loads facts and useful object IDs related to the hash
   algorithm(s) in use from the files in t/oid-info.

 - test_oid_cache

   This function reads per-hash algorithm information from standard
   input (usually a heredoc) in the format described in
   t/oid-info/README.  This is useful for test-specific values, such as
   object IDs, which must vary based on the hash algorithm.

   Certain fixed values, such as hash sizes and common placeholder
   object IDs, can be loaded with test_oid_init (described above).

 - test_oid <key>

   This function looks up a value for the hash algorithm in use, based
   on the key given.  The value must have been loaded using
   test_oid_init or test_oid_cache.  Providing an unknown key is an
   error.

 - yes [<string>]

   This is often seen in modern UNIX but some platforms lack it, so
   the test harness overrides the platform implementation with a
   more limited one.  Use this only when feeding a handful lines of
   output to the downstream---unlike the real version, it generates
   only up to 99 lines.

 - test_bool_env <env-variable-name> <default-value>

   Given the name of an environment variable with a bool value,
   normalize its value to a 0 (true) or 1 (false or empty string)
   return code.  Return with code corresponding to the given default
   value if the variable is unset.
   Abort the test script if either the value of the variable or the
   default are not valid bool values.


Prerequisites
-------------

These are the prerequisites that the test library predefines with
test_have_prereq.

See the prereq argument to the test_* functions in the "Test harness
library" section above and the "test_have_prereq" function for how to
use these, and "test_set_prereq" for how to define your own.

 - QUILT

   The `quilt` binary is avaialable on this system.

Tips for Writing Tests
----------------------

As with any programming projects, existing programs are the best
source of the information.  However, do _not_ emulate
t0000-basic.sh when writing your tests.  The test is special in
that it tries to validate the very core of Git.  For example, it
knows that there will be 256 subdirectories under .git/objects/,
and it knows that the object ID of an empty tree is a certain
40-byte string.  This is deliberately done so in t0000-basic.sh
because the things the very basic core test tries to achieve is
to serve as a basis for people who are changing the Git internal
drastically.  For these people, after making certain changes,
not seeing failures from the basic test _is_ a failure.  And
such drastic changes to the core Git that even changes these
otherwise supposedly stable object IDs should be accompanied by
an update to t0000-basic.sh.

However, other tests that simply rely on basic parts of the core
Git working properly should not have that level of intimate
knowledge of the core Git internals.  If all the test scripts
hardcoded the object IDs like t0000-basic.sh does, that defeats
the purpose of t0000-basic.sh, which is to isolate that level of
validation in one place.  Your test also ends up needing
updating when such a change to the internal happens, so do _not_
do it and leave the low level of validation to t0000-basic.sh.

Test coverage
-------------

You can use the coverage tests to find code paths that are not being
used or properly exercised yet.

To do that, run the coverage target at the top-level (not in the t/
directory):

    make coverage

That will run the test suite with each stg invocation capturing
coverage information. Coverage information from each stg invocation
is combined into a .coverage file which is used to generate
coverage reports.

A detailed HTML coverage report is generated in the "htmlcov"
directory, which you can then copy to a webserver, or inspect locally
in a browser.