LIT(1)

📦
version 22.1.8 · 6 versions
, in fedora 44

💖 LIT(1) — lit, the LLVM Integrated Tester 💖

okay bestie, pull up a chair — this is the manual for lit, section 1 of the manual pages, shipped with LLVM. It's the whole vibe of "I test your compiler and I tell you what broke." Let's go. 🦋

✨ NAME ✨

lit — the LLVM Integrated Tester 🎀

🌸 SYNOPSIS 🌸

lit [options] [tests]

💜 DESCRIPTION 💜

lit is a portable tool for executing LLVM and Clang style test suites, summarizing their results, and giving you an indication of failures. She is designed to be a lightweight testing tool with as simple a user interface as possible. No cap. 💅

You run lit with one or more tests to run specified on the command line. Tests can be either individual test files, or directories to search for tests — see TEST DISCOVERY for the deets. 🧚

Each specified test gets executed (potentially concurrently, she's multithreaded like that 😌) and once all tests have run, lit prints summary info on the number of tests that passed or failed — see TEST STATUS RESULTS. And bestie, listen: lit will exit with a non-zero exit code if any tests fail. Periodt. 😭

By default lit uses a succinct progress display and only prints summary info for test failures. Check OUTPUT OPTIONS for the options that control the progress display and output. ✨

lit also ships a bunch of options for controlling how tests are executed (specific features may depend on the particular test format). See EXECUTION OPTIONS for more. 🔥

And finally, lit also supports extra options for running only a subset of the options specified on the command line — see SELECTION OPTIONS. 👑

lit parses options from the environment variable LIT_OPTS after parsing options from the command line. LIT_OPTS is primarily useful for supplementing or overriding the command-line options supplied to lit by check targets defined by a project's build system. 🛠️

lit can also read options from response files, which you specify as inputs using the @path/to/file.rsp syntax. Arguments read from a file must be one per line, and are treated as if they were in the same place as the original file-referencing argument on the command line. A response file can reference other response files. 🪆 (yes, nesting, iconic)

If you're into the lit architecture or you're designing a lit testing implementation, go see LIT INFRASTRUCTURE. 🌈

⭐ GENERAL OPTIONS ⭐

  • -h, --help — show the lit help message and dip out. 🙈
  • --version — show lit's version number and exit.
  • -j N, --workers N — run N tests in parallel. By default this is automatically chosen to match the number of detected available CPUs. 🖥️✨
  • --config-prefix NAME — search for NAME.cfg and NAME.site.cfg when searching for test suites, instead of lit.cfg and lit.site.cfg. (yes you can rename the config files, main character energy)
  • -D NAME[=VALUE], --param NAME[=VALUE] — add a user defined parameter NAME with the given VALUE (or the empty string if you don't give one). The meaning and use of these parameters is test suite dependent. 🎀

🌈 OUTPUT OPTIONS 🌈

  • -q, --quiet — suppress any output except for test failures. 🤫
  • -s, --succinct — show less output, for example don't show information on tests that pass. Also shows a progress bar, unless --no-progress-bar is specified. 📊
  • -v, --verbose — show more information on test failures, for example the entire test output instead of just the test result. Each command is printed before it is executed. This can be valuable for debugging test failures, because the last printed command is the one that failed. Moreover, lit inserts 'RUN: at line N' after each command pipeline in the output to help you locate the source line of the failed command. 🔍
  • -vv, --echo-all-commands — deprecated alias for -v. (she's retired, don't use her 💀)
  • -a, --show-all — enable -v, but for all tests, not just failed tests. 👀
  • -o PATH, --output PATH — write test results to the provided path. 📝
  • --no-progress-bar — do not use the curses based progress bar.
  • --show-excluded — show excluded tests.
  • --show-skipped — show skipped tests.
  • --show-unsupported — show unsupported tests.
  • --show-pass — show passed tests. ✅
  • --show-flakypass — show passed with retry tests. (she wobbled but she made it 🫶)
  • --show-xfail — show expectedly failed tests. 😌

🔥 EXECUTION OPTIONS 🔥

  • --gtest-sharding — enable sharding for GoogleTest format.
  • --no-gtest-sharding — disable sharding for GoogleTest format.
  • --path PATH — specify an additional PATH to use when searching for executables in tests.
  • --vg — run individual tests under valgrind (using the memcheck tool). The --error-exitcode argument for valgrind is used so that valgrind failures will cause the program to exit with a non-zero status. When this option is enabled, lit will also automatically provide a "valgrind" feature that can be used to conditionally disable (or expect failure in) certain tests. 🧿
  • --vg-leak — when --vg is used, enable memory leak checks. When this option is enabled, lit will also automatically provide a "vg_leak" feature that can be used to conditionally disable (or expect failure in) certain tests. 💧
  • --vg-arg ARG — when --vg is used, specify an additional argument to pass to valgrind itself.
  • --no-execute — don't execute any tests (assume that they pass). (manifesting ✨)
  • --xunit-xml-output XUNIT_XML_OUTPUT — write XUnit-compatible XML test reports to the specified file.
  • --report-failures-only — only include failures (see TEST STATUS RESULTS) in the report.
  • --resultdb-output RESULTDB_OUTPUT — write LuCI ResultDB compatible JSON to the specified file.
  • --time-trace-output TIME_TRACE_OUTPUT — write Chrome tracing compatible JSON to the specified file
  • --timeout MAXINDIVIDUALTESTTIME — maximum time to spend running a single test (in seconds). 0 means no time limit. [Default: 0]
  • --timeout N — spend at most N seconds (approximately) running each individual test. 0 means no time limit, and 0 is the default. Note that this is not an alias for --max-time; the two are different kinds of maximums. ⏰
  • --max-failures MAX_FAILURES — stop execution after the given number of failures. 🛑
  • --max-retries-per-test N — retry running failed tests at most N times. Out of the following options to rerun failed tests, the --max-retries-per-test is the only one that doesn't require a change in the test scripts or the test config:
    • --max-retries-per-test lit option
    • config.test_retry_attempts test suite option
    • ALLOW_RETRIES: annotation in test script Any option in the list above overrules its predecessor. 🪜
  • --allow-empty-runs — do not fail the run if all tests are filtered out. 🫶
  • --per-test-coverage — emit the necessary test coverage data, divided per test case (involves setting a unique value to LLVM_PROFILE_FILE for each RUN). The coverage data files will be emitted in the directory specified by config.test_exec_root. 📈
  • --ignore-fail — exit with status zero even if some tests fail. (denial is a river in Egypt 💅)
  • --skip-test-time-recording — do not track elapsed wall time for each test.
  • --time-tests — track the wall time individual tests take to execute and include the results in the summary output. This is useful for determining which tests in a test suite take the most time to execute. ⏱️

✨ SELECTION OPTIONS ✨

okay so here's the vibe: by default lit is gonna run failing tests first, then run tests in descending execution time order to optimize concurrency. it's giving "let's fix the broken stuff while it's fresh". 💅 but bestie, you can change that execution order with the --order option, no cap.

the timing data lives in the test_exec_root in a file named .lit_test_times.txt. and if that file doesn't exist? lit goes and checks the test_source_root for the file, to optionally accelerate clean builds. considerate queen behavior honestly. 👑

  • --max-tests N — run at most N tests and then terminate. that's it, that's the whole thing.
  • --max-time N — spend at most N seconds (approximately) running tests and then terminate. ⏰ heads up tho: this is not an alias for --timeout, the two are different kinds of maximums, they're not the same girl, don't confuse them.
  • --order {lexical,random,smart} — define the order in which tests are run. the supported values are, and I need you to pay attention bestie:
    • lexical — tests will be run in lexical order according to the test file path. this option is useful when predictable test order is desired. very "i like my life organized" of you. 🎀
    • random — tests will be run in random order. chaos. iconic. no notes. 🦋
    • smart — tests that failed previously will be run first, then the remaining tests, all in descending execution time order. this is the default because it optimizes concurrency. main character energy fr fr.
  • --shuffle — run the tests in a random order, not failing/slowest first. Deprecated, use --order instead. it's giving 2014, we've moved on. 💀
  • -i, --incremental — run failed tests first (DEPRECATED: use --order=smart). yeah girl, the glow-up happened, use the new one. ✨
  • --filter REGEXP — run only those tests whose name matches the regular expression specified in REGEXP. and ooh, the environment variable LIT_FILTER can also be used in place of this option, which is especially useful in environments where the call to lit is issued indirectly. sneaky but valid. 🙈
  • --filter-out REGEXP — filter out those tests whose name matches the regular expression specified in REGEXP. and yes, the environment variable LIT_FILTER_OUT can also be used in place of this option, which is especially useful in environments where the call to lit is issued indirectly. it's the evil twin, we love her. 🖤
  • --filter-failed — run only those tests that previously failed. important: tests that have been newly added but not yet run are not included. so don't come for me when your brand new test didn't show up, okay? 😭
  • --xfail LIST — treat those tests whose name is in the semicolon separated list LIST as XFAIL. this can be helpful when one does not want to modify the test suite. the environment variable LIT_XFAIL can be also used in place of this option, which is especially useful in environments where the call to lit is issued indirectly.

a test name can specified as a file name relative to the test suite directory. for example:

LIT_XFAIL="affinity/kmp-hw-subset.c;offloading/memory_manager.cpp"

in this case, all of the following tests are treated as XFAIL:

libomp :: affinity/kmp-hw-subset.c
libomptarget :: nvptx64-nvidia-cuda :: offloading/memory_manager.cpp
libomptarget :: x86_64-pc-linux-gnu :: offloading/memory_manager.cpp

alternatively, a test name can be specified as the full test name reported in LIT output. for example, we can adjust the previous example not to treat the nvptx64-nvidia-cuda version of offloading/memory_manager.cpp as XFAIL:

LIT_XFAIL="affinity/kmp-hw-subset.c;libomptarget :: x86_64-pc-linux-gnu :: offloading/memory_manager.cpp"
  • --xfail-not LIST — do not treat the specified tests as XFAIL. the environment variable LIT_XFAIL_NOT can also be used in place of this option. the syntax is the same as for --xfail and LIT_XFAIL. and listen, --xfail-not and LIT_XFAIL_NOT always override all other XFAIL specifications, including an --xfail appearing later on the command line. the primary purpose is to suppress an XPASS result without modifying a test case that uses the XFAIL directive. she's the final boss of XFAIL decisions, periodt. 👑
  • --exclude-xfail — XFAIL tests won't be run, unless they are listed in the --xfail-not (or LIT_XFAIL_NOT) lists. simple as. 🌸
  • --num-shards M — divide the set of selected tests into M equal-sized subsets or "shards", and run only one of them. must be used with the --run-shard=N option, which selects the shard to run. the environment variable LIT_NUM_SHARDS can also be used in place of this option. these two options provide a coarse mechanism for partitioning large testsuites, for parallel execution on separate machines (say in a large testing farm). dividing the labor, we love to see it. 💪
  • --run-shard N — select which shard to run, assuming the --num-shards=M option was provided. the two options must be used together, and the value of N must be in the range 1..M. the environment variable LIT_RUN_SHARD can also be used in place of this option. bestie they're a package deal, you cannot split them up. 🫶

🌈 ADDITIONAL OPTIONS 🌈

  • --debug — run lit in debug mode, for debugging configuration issues and lit itself. detective mode activated. 🔍
  • --show-suites — list the discovered test suites and exit. no running, just listing. we're window shopping. ✨
  • --show-tests — list all of the discovered tests and exit. same energy, bigger list. 📋
  • --show-used-features — show all features used in the test suite (in XFAIL, UNSUPPORTED and REQUIRES) and exit. receipts, basically. 🧾
  • --update-tests — pass failing tests to functions in the lit_config.test_updaters list to check whether any of them know how to update the test to make it pass. it's giving "let the test fix itself", and honestly? slay. 💅

💖 EXIT STATUS 💖

so lit will exit with an exit code of 1 if there are any failures (see TEST STATUS RESULTS) and --ignore-fail has not been passed. otherwise, it will exit with the status 0. other exit codes are used for non-test related failures (for example a user error or an internal program error). so if you see a weird number, that's not a test being sad, that's something else going wrong entirely. 😭

🦋 TEST DISCOVERY 🦋

the inputs passed to lit can be either individual tests, or entire directories or hierarchies of tests to run. when lit starts up, the first thing it does is convert the inputs into a complete list of tests to run as part of test discovery. like making a to-do list but make it ✨automatic✨.

in the lit model, every test must exist inside some test suite. lit resolves the inputs specified on the command line to test suites by searching upwards from the input path until it finds a lit.cfg or lit.site.cfg file. these files serve as both a marker of test suites and as configuration files which lit loads in order to understand how to find and run the tests inside the test suite. dual purpose, multi-talented, we stan. 👑

once lit has mapped the inputs into test suites it traverses the list of inputs adding tests for individual files and recursively searching for tests in directories. very thorough, very "i check everywhere".

this behavior makes it easy to specify a subset of tests to run, while still allowing the test suite configuration to control exactly how tests are interpreted. in addition, lit always identifies tests by the test suite they are in, and their relative path inside the test suite. for appropriately configured projects, this allows lit to provide convenient and flexible support for out-of-tree builds. flexible queen behavior. 🌸

💅 TEST STATUS RESULTS 💅

each test ultimately produces one of the following eight results, and you need to know all of them, bestie, there will be a quiz:

PASS

the test succeeded. we love a win. 🎉

FLAKYPASS

the test succeeded after being re-run more than once. this only applies to tests containing an ALLOW_RETRIES: annotation. she was being dramatic and then pulled through. 🙈

XFAIL

the test failed, but that is expected. this is used for test formats which allow specifying that a test does not currently work, but wish to leave it in the test suite. it's not a bug, it's a known situation. 🫶

XPASS

the test succeeded, but it was expected to fail. this is used for tests which were specified as expected to fail, but are now succeeding (generally because the feature they test was broken and has been fixed). surprise success, honestly kind of iconic. ✨

FAIL

the test failed. no sugarcoating. 💀

UNRESOLVED

the test result could not be determined. for example, this occurs when the test could not be run, the test itself is invalid, or the test was interrupted. it's giving "we don't know her". 🤷

UNSUPPORTED

the test is not supported in this environment. this is used by test formats which can report unsupported tests. not her fault, wrong venue. 🚫

TIMEOUT

the test was run, but it timed out before it was able to complete. she took too long and the clock said no. ⏰

unresolved (UNRESOLVED), timed out (TIMEOUT), failed (FAIL) and unexpectedly passed (XPASS) tests are considered failures. that's the official fail list, memorize it. 📝

depending on the test format tests may produce additional information about their status (generally only for failures). see the OUTPUT OPTIONS section for more information.

🧚 LIT INFRASTRUCTURE 🧚

this section describes the lit testing architecture for users interested in creating a new lit testing implementation, or extending an existing one. so like, for the builders, the shapers, the girlies writing their own configs. 💜

lit proper is primarily an infrastructure for discovering and running arbitrary tests, and to expose a single convenient interface to these tests. lit itself doesn't know how to run tests, rather this logic is defined by test suites. she's the stage, not the performer. 🎭

⭐ TEST SUITES ⭐

as described in TEST DISCOVERY, tests are always located inside a test suite. test suites serve to define the format of the tests they contain, the logic for finding those tests, and any additional information to run the tests.

lit identifies test suites as directories containing lit.cfg or lit.site.cfg files (see also --config-prefix). test suites are initially discovered by recursively searching up the directory hierarchy for all the input files passed on the command line. you can use --show-suites to display the discovered test suites at startup.

once a test suite is discovered, its config file is loaded. config files themselves are Python modules which will be executed. when the config file is executed, two important global variables are predefined:

  • lit_config — the global lit configuration object (a LitConfig instance), which defines the builtin test formats, global configuration parameters, and other helper routines for implementing test configurations.
  • config — this is the config object (a TestingConfig instance) for the test suite, which the config file is expected to populate. the following variables are also available on the config object, some of which must be set by the config and others are optional or predefined:
    • name [required] — the name of the test suite, for use in reports and diagnostics.
    • test_format [required] — the test format object which will be used to discover and run tests in the test suite. generally this will be a builtin test format available from the lit.formats module.
    • test_source_root — the filesystem path to the test suite root. for out-of-dir builds this is the directory that will be scanned for tests.
    • test_exec_root — for out-of-dir builds, the path to the test suite root inside the object directory. this is where tests will be run and temporary output files placed.
    • environment — a dictionary representing the environment to use when executing tests in the suite.
  • standalone_tests — set this to true and you're marking a directory as "these tests run standalone, bestie, do NOT touch". Test discovery is disabled for that directory. And heads up: lit.suffixes and lit.excludes must be empty when this variable is true. No cap.
  • suffixes — for lit test formats that scan directories looking for tests, this is the list of suffixes used to identify test files. Used by: ShTest. 💅
  • substitutions — for lit test formats that substitute variables into a test script, this is the list of substitutions to perform. Used by: ShTest. ✨
  • unsupported — marks a directory as unsupported, so literally every test inside it gets reported as unsupported. Used by: ShTest. It's giving "we don't do that here" 🚫
  • parent — the parent configuration. It's the config object for the directory that contains the test suite, or None. 🫶
  • root — the root configuration. This is the top-most lit configuration in the whole project, the main character of the config chain 👑
  • pipefail — okay so normally, a test that uses a shell pipe fails if any of the commands on the pipe fail. If that's not what you want, setting this variable to false makes the test fail only if the last command in the pipe fails. Pick your fighter 💀
  • available_features — a set of features you can use in XFAIL, REQUIRES, and UNSUPPORTED directives. Your little feature menu 🌸

🔍 TEST DISCOVERY 🔍

So once the test suites are located, lit goes on a little recursive journey through the source directory (following test_source_root, obviously) looking for tests. 🦋

The way that it works: when lit enters a sub-directory, it first checks whether a nested test suite is defined in that directory. If yes? It loads that test suite recursively. If no? It instantiates a local test config for the directory instead (peep LOCAL CONFIGURATION FILES below, iykyk).

Tests are identified by the test suite they live inside, plus the relative path inside that suite. And important: that relative path may not refer to an actual file on disk. Some test formats (looking at you, GoogleTest) define "virtual tests" whose path contains both the path to the actual test file and a subpath that identifies the virtual test. Two things in one path, iconic behavior fr fr 💅

🎀 LOCAL CONFIGURATION FILES 🎀

When lit loads a subdirectory in a test suite, it instantiates a local test configuration by cloning the configuration for the parent directory — and the root of this configuration chain will always be a test suite. Periodt.

Once the test configuration is cloned, lit checks for a lit.local.cfg file in the subdirectory. If it's there, that file gets loaded and can be used to specialize the configuration for each individual directory. 🌈

So what's it for? This facility can be used to define subdirectories of optional tests, or to change other configuration parameters — for example, to change the test format, or the suffixes which identify test files. Obsessed with the flexibility honestly 🫶

✨ SUBSTITUTIONS ✨

okay bestie, this is the fun part 💅 lit lets you substitute patterns right inside your RUN commands. It also hands you this whole base set of substitutions for free, all defined in TestRunner.py:

  • %s — source path (the path to the file that's currently being run) 🫶
  • %S — source dir (the directory of the file currently being run)
  • %p — same as %S, literally
  • %{pathsep} — path separator
  • %{fs-src-root} — root component of file system paths that point to the LLVM checkout
  • %{fs-tmp-root} — root component of file system paths that point to the test's temporary directory
  • %{fs-sep} — file system path separator
  • %t — a path unique to the test (which you can use to make files or directories) ✨
  • %basename_t — the last path component of %t but without the .tmp extension (deprecated, use %{t:stem} instead) ⚠️
  • %% — just a %
  • %/s — %s but with \ replaced by /
  • %/S — %S but with \ replaced by /
  • %/p — %p but with \ replaced by /
  • %/t — %t but with \ replaced by /
  • %{s:basename} — the last path component of %s
  • %{t:stem} — the last path component of %t but without the .tmp extension (alias for %basename_t)
  • %{s:real} — %s after expanding all symbolic links and substitute drives
  • %{S:real} — %S after expanding all symbolic links and substitute drives
  • %{p:real} — %p after expanding all symbolic links and substitute drives
  • %{t:real} — %t after expanding all symbolic links and substitute drives
  • %{/s:real} — %/s after expanding all symbolic links and substitute drives
  • %{/S:real} — %/S after expanding all symbolic links and substitute drives
  • %{/p:real} — %/p after expanding all symbolic links and substitute drives
  • %{/t:real} — %/t after expanding all symbolic links and substitute drives
  • %{/s:regex_replacement} — %/s but escaped for use in the replacement of a s@@@ command in sed
  • %{/S:regex_replacement} — %/S but escaped for use in the replacement of a s@@@ command in sed
  • %{/p:regex_replacement} — %/p but escaped for use in the replacement of a s@@@ command in sed
  • %{/t:regex_replacement} — %/t but escaped for use in the replacement of a s@@@ command in sed
  • %:s — on Windows, %/s but a : is removed if it's the second character. Otherwise, %s but with a single leading / removed.
  • %:S — on Windows, %/S but a : is
  • the %S-flavored one, whose row got sliced in half by the page break — on Windows, a : gets removed if it's the second character. Otherwise, it's %S but with a single leading / removed. 💅
  • %:p — on Windows, %/p but a : is removed if it's the second character. Otherwise, %p but with a single leading / removed.
  • %:t — on Windows, %/t but a : is removed if it's the second character. Otherwise, %t but with a single leading / removed.
  • %{readfile:<filename>} — reads the file specified. that's it, that's the whole job, iconic behavior. 🫶

Other substitutions are provided that are variations on this base set, and further substitution patterns can be defined by each test module. See the modules LOCAL CONFIGURATION FILES. 👀

More detailed information on substitutions can be found in the LLVM Testing Infrastructure Guide <>. (yes bestie, that link renders as literally <> in here, not my fault, go find the guide, iykyk 🌸)

📊 TEST RUN OUTPUT FORMAT 📊

The lit output for a test run conforms to the following schema, in both short and verbose modes (although in short mode no PASS lines will be shown, so don't panic when they ghost you 💀). This schema has been chosen to be relatively easy to reliably parse by a machine (for example in buildbot log scraping), and for other tools to generate. no cap, it's built for robots to read. 🤖

Each test result is expected to appear on a line that matches:

<result code>: <test name> (<progress info>)

where <result-code> is a standard test result such as PASS, FAIL, XFAIL, XPASS, UNRESOLVED, or UNSUPPORTED. The performance result codes of IMPROVED and REGRESSED are also allowed. 👑

The <test name> field can consist of an arbitrary string containing no newline.

The <progress info> field can be used to report progress information such as (1/300) or can be empty, but even when empty the parentheses are required. them's the rules. ✨

Should a test be allowed retries (see ALLOW_RETRIES: annotation) and it needed more than one attempt to succeed, then <progress info> is extended by this information:

, <num_attempts_made> of <max_allowed_attempts> attempts

Each test result may include additional (multiline) log information in the following format:

<log delineator> TEST '(<test name>)' <trailing delineator>
... log message ...
<log delineator>

where <test name> should be the name of a preceding reported test, <log delineator> is a string of * characters at least four characters long (the recommended length is 20), and <trailing delineator> is an arbitrary (unparsed) string. star girl behavior, honestly ⭐

The following is an example of a test run output which consists of four tests A, B, C, and D, and a log message for the failing test C:

PASS: A (1 of 4)
PASS: B (2 of 4)
FAIL: C (3 of 4)
******************** TEST 'C' FAILED ********************
Test 'C' failed as a result of exit code 1.
********************
PASS: D (4 of 4)

✨ DEFAULT FEATURES ✨

For convenience, lit automatically adds available_features for some common use cases. she's thoughtful like that. 🎀

lit adds a feature based on the operating system being built on, for example: system-darwin, system-linux, etc. lit also automatically adds a feature based on the current architecture, for example target-x86_64, target-aarch64, etc.

When building with sanitizers enabled, lit automatically adds the short name of the sanitizer, for example: asan, tsan, etc. 🧼

To see the full list of features that can be added, see llvm/utils/lit/lit/llvm/config.py. (yes, go read the source, it's giving main character file 📂)

🧪 LIT EXAMPLE TESTS 🧪

The lit distribution contains several example implementations of test suites in the ExampleTests directory. copy her homework, she won't mind, it's literally there for you 🦋

👀 SEE ALSO 👀

💖 Author 💖

Maintained by the LLVM Team (https://llvm.org/).

2003-2026, LLVM Project

okay bestie that's the WHOLE page, you made it to the end, so proud of you 🥹 and that lil footer at the bottom? it's the LIT(1) page, page 22, dated 2026-07-16. the source and version, in the flesh, right where the man reader puts it. periodt. 💅🌈🫶
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