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At GitHub, we've got a real-world repository that has been triggering
failures of the form:
git: merge-ort.c:3007: process_renames: Assertion `newinfo && !newinfo->merged.clean' failed.
which comes from the line:
VERIFY_CI(newinfo);
Unfortunately, this one has been quite complex to unravel, and is a
bit complex to explain. So, I'm going to carefully try to explain each
relevant piece needed to understand the fix, then carefully build up
from a simple testcase to some of the relevant testcases.
== New special case we need to consider ==
Rename pairs in the diffcore machinery connect the source path of a
rename with the destination path of a rename. Since we have rename
pairs to consider on both sides of history since the merge base,
merging has to consider a few special cases of possible overlap:
A) two rename pairs having the same target path
B) two rename pairs having the same source path
C) the source path of one rename pair being the target path of a
different rename pair
Some of these came up often enough that we gave them names:
A) a rename/rename(2to1) conflict (looks similar to an add/add conflict)
B) a rename/rename(1to2) conflict, which represents the same path being
renamed differently on the two sides of history
C) not yet named
merge-ort is well-prepared to handle cases (A) and (B), as was
merge-recursive (which was merge-ort's predecessor). Case (C) was
briefly considered during the years of merge-recursive maintenance,
but the full extent of support it got was a few FIXME/TODO comments
littered around the code highlighting some of the places that would
probably need to be fixed to support it. When I wrote merge-ort I
ignored case (C) entirely, since I believed that case (C) was only
possible if we were to support break detection during merges. Not
only had break detection never been supported by any merge algorithm,
I thought break detection wasn't worth the effort to support in a
merge algorithm. However, it turns out that case (C) can be triggered
without break detection, if there's enough moving pieces.
Before I dive into how to trigger case (C) with directory renames plus
other renames, it might be helpful to use a simpler example with break
detection first. And before we get to that it may help to explain
some more basics of handling renames in the merge algorithm. So, let
me first backup and provide a quick refresher on each of
* handling renames
* what break detection would mean, if supported in merging
* handling directory renames
From there, I'll build up from a basic directory rename detection case
to one that triggers a failure currently.
== Handling renames ==
In the merge machinery when we have a rename of a path A -> B,
processing that rename needs to remove path A, and make sure that path B
has the relevant information. Note that if the content was also
modified on both sides, this may mean that we have 3 different stages
that need to be stored at path B instead of having some stored at path
A.
Having all stages stored at path B makes it much easier for users to
investigate and resolve the content conflict associated with a renamed
path. For example:
* "git status" doesn't have to figure out how to list paths A & B and
attempt to connect them for users; it can just list path B.
* Users can use "git ls-files -u B" (instead of trying to find the
previous name of the file so they can list both, i.e. "git ls-files
-u A B")
* Users can resolve via "git add B" (without needing to "git rm A")
== What break detection would mean ==
If break detection were supported, we might have cases where A -> B
*and* C -> A, meaning that both rename pairs might believe they need to
update A. In particular, the processing of A -> B would need to be
careful to not clear out all stages of A and mark it resolved, while
both renames would need to figure out which stages of A belong with A
and which belong with B, so that both paths have the right stages
associated with them.
merge-ort (like merge-recursive before it) makes no attempt to handle
break detection; it runs with break detection turned off. It would
need to be retrofitted to handle such cases.
== Directory rename detection ==
If one side of history renames directory D/ -> E/, and the other side of
history adds new files to D/, then directory rename detection notices
and suggests moving those new files to E/. A similar thing is done for
paths renamed into D/, causing them to be transitively renamed into E/.
The default in the merge machinery is to report a conflict whenever a
directory rename might modify the location of a path, so that users can
decide whether they wanted the original path or the
directory-rename-induced location. However, that means the default
codepath still runs through all the directory rename detection logic, it
just supplements it with providing conflict notices when it is done.
== Building up increasingly complex testcases ==
I'll start with a really simple directory rename example, and then
slowly add twists that explain new pieces until we get to the
problematic cases:
=== Testcase 1 ===
Let's start with a concrete example, where particular files/directories of
interest that exist or are changed on each side are called out:
Original: <nothing of note>
our side: rename B/file -> C/file
their side: rename C/ -> A/
For this case, we'd expect to see the original B/file appear not at
C/file but at A/file.
(We would also expect a conflict notice that the user will want to
choose between C/file and A/file, but I'm going to ignore conflict
notices from here on by assuming merge.directoryRenames is set to
`true` rather than `conflict`; the only difference that assumption
makes is whether that makes the merge be considered to be conflicted
and whether it prints a conflict notice; what is written to the index
or working directory is unchanged.)
=== Testcase 2 ===
Modify testcase 1 by having A/file exist from the start:
Original: A/file exists
our side: rename B/file -> C/file
their side: rename C/ -> A/
In such a case, to avoid user confusion at what looks kind of like an
add/add conflict (even though the original path at A/file was not added
by either side of the merge), we turn off directory rename detection for
this path and print a "in the way" warning to the user:
CONFLICT (implicit dir rename): Existing file/dir ... in the way ...
The testcases in section 5 of t6423 explore these in more detail.
=== Testcase 3 ===
Let's modify testcase 1 in a slightly different way: have A/file be
added by their side rather than it already existing.
Original: <nothing of note>
our side: rename B/file -> C/file
their side: rename C/ -> A/
add A/file
In this case, the directory rename detection basically transforms our
side's original B/file -> C/file into a B/file -> A/file, and so we
get a rename/add conflict, with one version of A/file coming from the
renamed file, and another coming from the new A/file, each stored as
stages 2 and 3 in conflicts. This kind of add/add conflict is perhaps
slightly more complex than a regular add/add conflict, but with the
printed messages it makes sense where it came from and we have
different stages of the file to work with to resolve the conflict.
=== Testcase 4 ===
Let's do something similar to testcase 3, but have the opposite side of
history add A/file:
Original: <nothing of note>
our side: rename B/file -> C/file
add A/file
their side: rename C/ -> A/
Now if we allow directory rename detection to modify C/file to A/file,
then we also get a rename/add conflict, but in this case we'd need both
higher order stages being recorded on side 2, which makes no sense. The
index can't store multiple stage 2 entries, and even if we could, it
would probably be confusing for users to work with. So, similar to what
we do when there was an A/file in the original version, we simply turn
off directory rename detection for cases like this and provide the "in
the way" CONFLICT notice to the user.
=== Testcase 5 ===
We're slowly getting closer. Let's mix it up by having A/file exist at
the beginning but not exist on their side:
original: A/file exists
our side: rename B/file -> C/file
their side: rename C/ -> A/
rename A/file -> D/file
For this case, you could say that since A/file -> D/file, it's no longer
in the way of C/file being moved by directory rename detection to
A/file. But that would give us a case where A/file is both the source
and the target of a rename, similar to break detection, which the code
isn't currently equipped to handle.
This is not yet the case that causes current failures; to the current
code, this kind of looks like testcase 4 in that A/file is in the way
on our side (since A/file was in the original and was umodified by our
side). So, it results in a "in the way" notification with directory
rename detection being turned off for A/file so that B/file ends up at
C/file.
Perhaps the resolution could be improved in the future, but our "in
the way" checks prevented such problems by noticing that A/file exists
on our side and thus turns off directory rename detection from
affecting C/file's location. So, while the merge result could be
perhaps improved, the fact that this is currently handled by giving
the user an "in the way" message gives the user a chance to resolve
and prevents the code from tripping itself up.
=== Testcase 6 ===
Let's modify testcase 5 a bit more, to also delete A/file on our side:
original: A/file exists
our side: rename B/file -> C/file
delete A/file
their side: rename C/ -> A/
rename A/file -> D/file
Now the "in the way" logic doesn't detect that there's an A/file in
the way (neither side has an A/file anymore), so it's fine to
transitively rename C/file further to A/file...except that we end up
with A/file being both the source of one rename, and the target of a
different rename. Each rename pair tries to handle the resolution of
the source and target paths of its own rename. But when we go to
process the second rename pair in process_renames(), we do not expect
either the source or the destination to be marked as handled already;
so, when we hit the sanity checks that these are not handled:
VERIFY_CI(oldinfo);
VERIFY_CI(newinfo);
then one of these is going to throw an assertion failure since the
previous rename pair already marked both of its paths as handled.
This will give us an error of the form:
git: merge-ort.c:3007: process_renames: Assertion `newinfo && !newinfo->merged.clean' failed.
This is the failure we're currently triggering, and it fundamentally
depends on:
* a path existing in the original
* that original path being removed or renamed on *both* sides
* some kind of directory rename moving some *other* path into that
original path
This was added as testcase 12q in t6423.
=== Testcase 7 ===
Bonus bug found while investigating!
Let's go back to the comparison between testcases 2 & 3, and set up a
file present on their side that we need to consider:
Original: A/file exists
our side: rename B/file -> C/file
rename A/file -> D/file
their side: rename C/ -> A/
Here, there is no A/file in the way on our side like testcase 4.
There is an A/file present on their side like testcase 3, which was an
add/add conflict, but that's associated with the file be renamed to
D/file. So, that really shouldn't be an add/add conflict because we
instead want all modes of the original A/file to be transported to
D/file.
Unfortunately, the current code kind of treats it like an add/add
conflict instead...but even worse. There is also a valid mode for
A/file in the original, which normally goes to stage 1. However, an
add/add conflict should be represented in the index with no mode at
stage 1 (for the original side), only modes at stages 2 and 3 (for our
and their side), so for an add/add we'd expect that mode for A/file in
the original version to be cleared out (or be transported to D/file).
Unfortunately, the code currently leaves not only the stage 3 entry
for A/file intact, it also leaves the stage 1 entry for A/file. This
results in `git ls-files -u A/file` output of the form:
100644 d00491fd7e5bb6fa28c517a0bb32b8b506539d4d 1 A/file
100644 0cfbf08886fca9a91cb753ec8734c84fcbe52c9f 2 A/file
100644 d00491fd7e5bb6fa28c517a0bb32b8b506539d4d 3 A/file
This would likely cause users to believe this isn't an add/add
conflict; rather, this would lead them to believe that A/file was only
modified on our side and that therefore it should not have been a
conflict in the first place. And while resolving the conflict in
favor of our side is the correct resolution (because stages 1 and 3
should have been cleared out in the first place), this is certainly
likely to cause confusion for anyone attempting to investigate why
this path was marked as conflicted.
This was added as testcase 12p in t6423.
== Attempted solutions that I discarded ==
1) For each side of history, create a strset of the sources of each
rename on the other side of history. Then when using directory
renames to modify existing renames, verify that we aren't renaming
to a source of another rename.
Unfortunately, the "relevant renames" optimization in merge-ort
means we often don't detect renames -- we just see a delete and an
add -- which is easy to forget and makes debugging testcases harder,
but it also turns out that this solution in insufficient to solve
the related problems in the area (more on that below).
2) Modify the code to be aware of the possibility of renaming to
the source of another side's rename, and make all the conflict
resolution logic for each case (including existing
rename/rename(2to1) and rename/rename(1to2) cases) handle the
additional complexity. It turns out there was much more code to
audit than I wanted, for a really niche case. I didn't like how
many changes were needed, and aborted.
== Solution ==
We do not want the stages of unrelated files appearing at the same path
in the index except when dealing with an add/add conflict. While we
previously handled this for stages 2 & 3, we also need to worry about
stage 1. So check for a stage 1 index entry being in the way of a
directory rename.
However, if we can detect that the stage 1 index entry is actually from
a related file due to a directory-rename-causes-rename-to-self
situation, then we can allow the stage 1 entry to remain.
From this wording, you may note that it's not just rename cases that
are a problem; bugs could be triggered with directory renames vs simple
adds. That leads us to...
== Testcases 8+ ==
Another bonus bug, found via understanding our final solutions (and the
failure of our first attempted solution)!
Let's tweak testcase 7 a bit:
Original: A/file exists
our side: delete A/file
add -> C/file
their side: delete A/file
rename C/ -> A/
Here, there doesn't seem to be a big problem. Sure C/file gets modified
via the directory rename of C/ -> A/ so that it becomes A/file, but
there's no file in the way, right? Actually, here we have a problem
that the stage 1 entry of A/file would be combined with the stage 2
entry of C/file, and make it look like a modify/delete conflict.
Perhaps there is some extra checking that could be added to the code to
make it attempt to clear out the stage 1 entry of A/file, but the
various rename-to-self-via-directory-rename testcases make that a bit
more difficult. For now, it's easier to just treat this as a
path-in-the-way situation and not allow the directory rename to modify
C/file.
That sounds all well and good, but it does have an interesting side
effect. Due to the "relevant renames" optimizations in merge-ort (i.e.
only detect the renames you need), 100% renames whose files weren't
modified on the other side often go undetected. This means that if we
modify this testcase slightly to:
Original: A/file exists
our side: A/file -> C/file
their side: rename C/ -> A/
Then although this looks like where the directory rename just moves
C/file back to A/file and there's no problem, we may not detect the
A/file -> C/file rename. Instead it will look like a deletion of A/file
and an addition of C/file. The directory rename then appears to be
moving C/file to A/file, which is on top of an "unrelated" file (or at
least a file it doesn't know is related). So, we will report
path-in-the-way conflicts now in cases where we didn't before. That's
better than silently and accidentally combining stages of unrelated
files and making them look like a modify/delete; users can investigate
the reported conflict and simply resolve it.
This means we tweak the expected solution for testcases 12i, 12j, and
12k. (Those three tests are basically the same test repeated three
times, but I was worried when I added those that subtle differences in
parent/child, sibling/sibling, and toplevel directories might mess up
how rename-to-self testcases actually get handled.)
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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
t/Makefile defines a target for each test file, such that you can also use
shell pattern matching to run a subset of the tests:
make *checkout*
will run all tests with 'checkout' in their filename.
Since the tests all output TAP (see https://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.
GIT_PROVE_OPTS can be used to pass additional options, e.g.
$ make DEFAULT_TEST_TARGET=prove GIT_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 GIT_TEST_OPTS
appropriately before running "make". Short options can be bundled, i.e.
'-d -v' is the same as '-dv'.
-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.
--valgrind=<tool>::
Execute all Git binaries under valgrind tool <tool> and exit
with status 126 on errors (just like regular tests, this will
only stop the test script when running under -i).
Since it makes no sense to run the tests with --valgrind and
not see any output, this option implies --verbose. For
convenience, it also implies --tee.
<tool> defaults to 'memcheck', just like valgrind itself.
Other particularly useful choices include 'helgrind' and
'drd', but you may use any tool recognized by your valgrind
installation.
As a special case, <tool> can be 'memcheck-fast', which uses
memcheck but disables --track-origins. Use this if you are
running tests in bulk, to see if there are _any_ memory
issues.
Note that memcheck is run with the option --leak-check=no,
as the git process is short-lived and some errors are not
interesting. In order to run a single command under the same
conditions manually, you should set GIT_VALGRIND to point to
the 't/valgrind/' directory and use the commands under
't/valgrind/bin/'.
--valgrind-only=<pattern>::
Like --valgrind, 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.
--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`.
--with-dashes::
By default tests are run without dashed forms of
commands (like git-commit) in the PATH (it only uses
wrappers from ../bin-wrappers). Use this option to include
the build directory (..) in the PATH, which contains all
the dashed forms of commands. This option is currently
implied by other options like --valgrind and
GIT_TEST_INSTALLED.
--no-bin-wrappers::
By default, the test suite uses the wrappers in
`../bin-wrappers/` to execute `git` and friends. With this option,
`../git` and friends are run directly. This is not recommended
in general, as the wrappers contain safeguards to ensure that no
files from an installed Git are used, but can speed up test runs
especially on platforms where running shell scripts is expensive
(most notably, Windows).
--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.
--chain-lint::
--no-chain-lint::
If --chain-lint is enabled, the test harness will check each
test to make sure that it properly "&&-chains" all commands (so
that a failure in the middle does not go unnoticed by the final
exit code of the test). This check is performed in addition to
running the tests themselves. You may also enable or disable
this feature by setting the GIT_TEST_CHAIN_LINT environment
variable to "1" or "0", respectively.
--stress::
Run the test script repeatedly in multiple parallel jobs until
one of them fails. Useful for reproducing rare failures in
flaky tests. The number of parallel jobs is, in order of
precedence: the value of the GIT_TEST_STRESS_LOAD
environment variable, or twice the number of available
processors (as shown by the 'getconf' utility), or 8.
Implies `--verbose -x --immediate` to get the most information
about the failure. Note that the verbose output of each test
job is saved to 't/test-results/$TEST_NAME.stress-<nr>.out',
and only the output of the failed test job is shown on the
terminal. The names of the trash directories get a
'.stress-<nr>' suffix, and the trash directory of the failed
test job is renamed to end with a '.stress-failed' suffix.
--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 GIT_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.
When using GIT_TEST_INSTALLED, you can also set GIT_TEST_EXEC_PATH to
override the location of the dashed-form subcommands (what
GIT_EXEC_PATH would be used for during normal operation).
GIT_TEST_EXEC_PATH defaults to `$GIT_TEST_INSTALLED/git --exec-path`.
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
$ GIT_SKIP_TESTS=t9200.8 sh ./t9200-git-cvsexport-commit.sh
and even:
$ GIT_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, <test-selector>, is a list of description
substrings or globs or individual test numbers or ranges with an
optional negation prefix (of '!') that define what tests in a test
suite to include (or exclude, if negated) in the run. A range is two
numbers separated with a dash and specifies an inclusive range of tests
to run. You may omit the first or the second number to
mean "from the first test" or "up to the very last test" respectively.
The argument to --run is split on commas into separate strings,
numbers, and ranges, and picks all tests that match any of the
individual selection criteria. If the substring of the description
text that you want to match includes a comma, use the glob character
'?' instead. For example --run='rebase,merge?cherry-pick' would match
on all tests that match either the glob *rebase* or the glob
*merge?cherry-pick*.
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.
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'
Sometimes there may be multiple tests with e.g. "setup" in their name
that are needed and rather than figuring out the number for all of them
we can just use "setup" as a substring/glob to match against the test
description:
$ sh ./t0050-filesystem.sh --run=setup,9-11
or one could select both the setup tests and the rename ones (assuming all
relevant tests had those words in their descriptions):
$ sh ./t0050-filesystem.sh --run=setup,rename
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 GIT_TEST_
environment set.
GIT_TEST_FAIL_PREREQS=<boolean> fails all prerequisites. This is
useful for discovering issues with the tests where say a later test
implicitly depends on an optional earlier test.
There's a "FAIL_PREREQS" prerequisite that can be used to test for
whether this mode is active, and e.g. skip some tests that are hard to
refactor to deal with it. The "SYMLINKS" prerequisite is currently
excluded as so much relies on it, but this might change in the future.
GIT_TEST_SPLIT_INDEX=<boolean> forces split-index mode on the whole
test suite. Accept any boolean values that are accepted by git-config.
GIT_TEST_PROTOCOL_VERSION=<n>, when set, makes 'protocol.version'
default to n.
GIT_TEST_FULL_IN_PACK_ARRAY=<boolean> exercises the uncommon
pack-objects code path where there are more than 1024 packs even if
the actual number of packs in repository is below this limit. Accept
any boolean values that are accepted by git-config.
GIT_TEST_OE_SIZE=<n> exercises the uncommon pack-objects code path
where we do not cache object size in memory and read it from existing
packs on demand. This normally only happens when the object size is
over 2GB. This variable forces the code path on any object larger than
<n> bytes.
GIT_TEST_OE_DELTA_SIZE=<n> exercises the uncommon pack-objects code
path where deltas larger than this limit require extra memory
allocation for bookkeeping.
GIT_TEST_VALIDATE_INDEX_CACHE_ENTRIES=<boolean> checks that cache-tree
records are valid when the index is written out or after a merge. This
is mostly to catch missing invalidation. Default is true.
GIT_TEST_COMMIT_GRAPH=<boolean>, when true, forces the commit-graph to
be written after every 'git commit' command, and overrides the
'core.commitGraph' setting to true.
GIT_TEST_COMMIT_GRAPH_CHANGED_PATHS=<boolean>, when true, forces
commit-graph write to compute and write changed path Bloom filters for
every 'git commit-graph write', as if the `--changed-paths` option was
passed in.
GIT_TEST_FSMONITOR=$PWD/t7519/fsmonitor-all exercises the fsmonitor
code paths for utilizing a (hook based) file system monitor to speed up
detecting new or changed files.
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).
GIT_TEST_PACK_USE_BITMAP_BOUNDARY_TRAVERSAL=<boolean> if enabled will
use the boundary-based bitmap traversal algorithm. See the documentation
of `pack.useBitmapBoundaryTraversal` for more details.
GIT_TEST_PACK_SPARSE=<boolean> if disabled will default the pack-objects
builtin to use the non-sparse object walk. This can still be overridden by
the --sparse command-line argument.
GIT_TEST_PRELOAD_INDEX=<boolean> exercises the preload-index code path
by overriding the minimum number of cache entries required per thread.
GIT_TEST_INDEX_THREADS=<n> enables exercising the multi-threaded loading
of the index for the whole test suite by bypassing the default number of
cache entries and thread minimums. Setting this to 1 will make the
index loading single threaded.
GIT_TEST_MULTI_PACK_INDEX=<boolean>, when true, forces the multi-pack-
index to be written after every 'git repack' command, and overrides the
'core.multiPackIndex' setting to true.
GIT_TEST_MULTI_PACK_INDEX_WRITE_INCREMENTAL=<boolean>, when true, sets
the '--incremental' option on all invocations of 'git multi-pack-index
write'.
GIT_TEST_SIDEBAND_ALL=<boolean>, when true, overrides the
'uploadpack.allowSidebandAll' setting to true, and when false, forces
fetch-pack to not request sideband-all (even if the server advertises
sideband-all).
GIT_TEST_DISALLOW_ABBREVIATED_OPTIONS=<boolean>, when true (which is
the default when running tests), errors out when an abbreviated option
is used.
GIT_TEST_DEFAULT_HASH=<hash-algo> specifies which hash algorithm to
use in the test scripts. Recognized values for <hash-algo> are "sha1"
and "sha256".
GIT_TEST_DEFAULT_REF_FORMAT=<format> specifies which ref storage format to use
in the test scripts. Recognized values for <format> are "files" and
"reftable".
GIT_TEST_NO_WRITE_REV_INDEX=<boolean>, when true disables the
'pack.writeReverseIndex' setting.
GIT_TEST_SPARSE_INDEX=<boolean>, when true enables index writes to use the
sparse-index format by default.
GIT_TEST_CHECKOUT_WORKERS=<n> overrides the 'checkout.workers' setting
to <n> and 'checkout.thresholdForParallelism' to 0, forcing the
execution of the parallel-checkout code.
GIT_TEST_FATAL_REGISTER_SUBMODULE_ODB=<boolean>, when true, makes
registering submodule ODBs as alternates a fatal action. Support for
this environment variable can be removed once the migration to
explicitly providing repositories when accessing submodule objects is
complete or needs to be abandoned for whatever reason (in which case the
migrated codepaths still retain their performance benefits).
GIT_TEST_REQUIRE_PREREQ=<list> allows specifying a space separated list of
prereqs that are required to succeed. If a prereq in this list is triggered by
a test and then fails then the whole test run will abort. This can help to make
sure the expected tests are executed and not silently skipped when their
dependency breaks or is simply not present in a new environment.
GIT_TEST_NAME_HASH_VERSION=<int>, when set, causes 'git pack-objects' to
assume '--name-hash-version=<n>'.
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.
Recommended style
-----------------
- Keep the test_expect_* function call and test title on
the same line.
For example, with test_expect_success, write it like:
test_expect_success 'test title' '
... test body ...
'
Instead of:
test_expect_success \
'test title' \
'... test body ...'
- End the line with an opening single quote.
- Indent here-document bodies, and use "<<-" instead of "<<"
to strip leading TABs used for indentation:
test_expect_success 'test something' '
cat >expect <<-\EOF &&
one
two
three
EOF
test_something > actual &&
test_cmp expect actual
'
Instead of:
test_expect_success 'test something' '
cat >expect <<\EOF &&
one
two
three
EOF
test_something > actual &&
test_cmp expect actual
'
- Quote or escape the EOF delimiter that begins a here-document if
there is no parameter or other expansion in it, to signal readers
that they can skim it more casually:
cmd <<-\EOF
literal here-document text without any expansion
EOF
Do's & don'ts
-------------
Here are a few examples of things you probably should and shouldn't do
when writing tests.
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 $TRASH_DIRECTORY. It makes a difference on
Windows, where the shell (MSYS bash) mangles absolute path names.
For details, see the commit message of 4114156ae9.
- Remember that inside the <script> part, the standard output and
standard error streams are discarded, and the test harness only
reports "ok" or "not ok" to the end user running the tests. Under
--verbose, they are shown to help debug the tests.
- Be careful when you loop
You may need to verify multiple things in a loop, but the
following does not work correctly:
test_expect_success 'test three things' '
for i in one two three
do
test_something "$i"
done &&
test_something_else
'
Because the status of the loop itself is the exit status of the
test_something in the last round, the loop does not fail when
"test_something" for "one" or "two" fails. This is not what you
want.
Instead, you can break out of the loop immediately when you see a
failure. Because all test_expect_* snippets are executed inside
a function, "return 1" can be used to fail the test immediately
upon a failure:
test_expect_success 'test three things' '
for i in one two three
do
test_something "$i" || return 1
done &&
test_something_else
'
Note that we still &&-chain the loop to propagate failures from
earlier commands.
- Repeat tests with slightly different arguments in a loop.
In some cases it may make sense to re-run the same set of tests with
different options or commands to ensure that the command behaves
despite the different parameters. This can be achieved by looping
around a specific parameter:
for arg in '' "--foo"
do
test_expect_success "test command ${arg:-without arguments}" '
command $arg
'
done
Note that while the test title uses double quotes ("), the test body
should continue to use single quotes (') to avoid breakage in case the
values contain e.g. quoting characters. The loop variable will be
accessible regardless of the single quotes as the test body is passed
to `eval`.
And here are the "don'ts:"
- Don't exit() within a <script> part.
The harness will catch this as a programming error of the test.
Use test_done instead if you need to stop the tests early (see
"Skipping tests" below).
- Don't use '! git cmd' when you want to make sure the git command
exits with failure in a controlled way by calling "die()". Instead,
use 'test_must_fail git cmd'. This will signal a failure if git
dies in an unexpected way (e.g. segfault).
On the other hand, don't use test_must_fail for running regular
platform commands; just use '! cmd'. We are not in the business
of verifying that the world given to us sanely works.
- Don't feed the output of a git command to a pipe, as in:
git -C repo ls-files |
xargs -n 1 basename |
grep foo
which will discard git's exit code and may mask a crash. In the
above example, all exit codes are ignored except grep's.
Instead, write the output of that command to a temporary
file with ">" or assign it to a variable with "x=$(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_expect_* 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. Some of them are listed below;
see test-lib-functions.sh for the full list and their options.
- 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 <script> is `-` (a single dash), then the script to run is read
from stdin. This lets you more easily use single quotes within the
script by using a here-doc. For example:
test_expect_success 'output contains expected string' - <<\EOT
grep "this string has 'quotes' in it" output
EOT
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 [options] <git-command>
Run a git command inside a debugger. This is primarily meant for
use when debugging a failing test script. With '-t', use your
original TERM instead of test-lib.sh's "dumb", so that your
debugger interface has colors.
- 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_lazy_prereq <prereq> <script>
Declare the way to determine if a test prerequisite <prereq> is
satisified or not, but delay the actual determination until the
prerequisite is actually used by "test_have_prereq" or the
three-arg form of the test_expect_* functions. For example, this
is how the SYMLINKS prerequisite is declared to see if the platform
supports symbolic links:
test_lazy_prereq SYMLINKS '
ln -s x y && test -h y
'
The script is lazily invoked when SYMLINKS prerequisite is first
queried by either "test_have_prereq SYMLINKS" or "test_expect_*
SYMLINKS ...". The script is run in a temporary directory inside
a subshell, so you do not have to worry about removing temporary
files you create there. When the script exits with status 0, the
prerequisite is set. Exiting with non-zero status other than 125
makes the prerequisite unsatisified. Exiting the script with 125
signals a programming error and is used to mark a prerequisite that
should not be used by test scripts.
- 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>
test_path_is_dir <path>
test_path_is_missing <path>
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.
- 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 [options]
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_path_is_executable
This tests whether a file is executable and prints an error message
if not. This must be used only under the POSIXPERM 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.
- PYTHON
Git wasn't compiled with NO_PYTHON=YesPlease. Wrap any tests that
need Python with this.
- PERL
Git wasn't compiled with NO_PERL=YesPlease.
Even without the PERL prerequisite, tests can assume there is a
usable perl interpreter at $PERL_PATH, though it need not be
particularly modern.
- POSIXPERM
The filesystem supports POSIX style permission bits.
- BSLASHPSPEC
Backslashes in pathspec are not directory separators. This is not
set on Windows. See 6fd1106a for details.
- EXECKEEPSPID
The process retains the same pid across exec(2). See fb9a2bea for
details.
- PIPE
The filesystem we're on supports creation of FIFOs (named pipes)
via mkfifo(1).
- SYMLINKS
The filesystem we're on supports symbolic links. E.g. a FAT
filesystem doesn't support these. See 704a3143 for details.
- SANITY
Test is not run by root user, and an attempt to write to an
unwritable file is expected to fail correctly.
- PCRE
Git was compiled with support for PCRE. Wrap any tests
that use git-grep --perl-regexp or git-grep -P in these.
- CASE_INSENSITIVE_FS
Test is run on a case insensitive file system.
- UTF8_NFD_TO_NFC
Test is run on a filesystem which converts decomposed utf-8 (nfd)
to precomposed utf-8 (nfc).
- PTHREADS
Git wasn't compiled with NO_PTHREADS=YesPlease.
- REFFILES
Test is specific to packed/loose ref storage, and should be
disabled for other ref storage backends
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 internals
drastically. For these people, after making certain changes,
not seeing failures from the basic test _is_ a failure. Any
Git core changes so drastic that they change even 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
an update whenever the internals change, 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'll compile Git with GCC's coverage arguments, and generate a test
report with gcov after the tests finish. Running the coverage tests
can take a while, since running the tests in parallel is incompatible
with GCC's coverage mode.
After the tests have run you can generate a list of untested
functions:
make coverage-untested-functions
You can also generate a detailed per-file HTML report using the
Devel::Cover module. To install it do:
# On Debian or Ubuntu:
sudo aptitude install libdevel-cover-perl
# From the CPAN with cpanminus
curl -L https://cpanmin.us/ | perl - --sudo --self-upgrade
cpanm --sudo Devel::Cover
Then, at the top-level:
make cover_db_html
That'll generate a detailed cover report in the "cover_db_html"
directory, which you can then copy to a webserver, or inspect locally
in a browser.