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lit - LLVM Integrated Tester


lit [options] [tests]


lit is a portable tool for executing LLVM and Clang style test suites, summarizing their
results, and providing indication of failures. lit is designed to be a lightweight
testing tool with as simple a user interface as possible.

lit should be run 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).

Each specified test will be executed (potentially in parallel) and once all tests have
been run lit will print summary information on the number of tests which passed or failed
(see TEST STATUS RESULTS). The lit program will execute with a non-zero exit code if any
tests fail.

By default lit will use a succinct progress display and will only print summary
information for test failures. See OUTPUT OPTIONS for options controlling the lit
progress display and output.

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

Finally, lit also supports additional options for only running a subset of the options
specified on the command line, see SELECTION OPTIONS for more information.

Users interested in the lit architecture or designing a lit testing implementation should


-h, --help
Show the lit help message.

-j N, --threads=N
Run N tests in parallel. By default, this is automatically chosen to match the
number of detected available CPUs.

Search for NAME.cfg and NAME.site.cfg when searching for test suites, instead of
lit.cfg and lit.site.cfg.

-D NAME, -D NAME=VALUE, --param NAME, --param NAME=VALUE
Add a user defined parameter NAME with the given VALUE (or the empty string if not
given). The meaning and use of these parameters is test suite dependent.


-q, --quiet
Suppress any output except for test failures.

-s, --succinct
Show less output, for example don't show information on tests that pass.

-v, --verbose
Show more information on test failures, for example the entire test output instead
of just the test result.

-a, --show-all
Show more information about all tests, for example the entire test commandline and

Do not use curses based progress bar.

Show the names of unsupported tests.

Show the names of tests that were expected to fail.


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

When --vg is used, specify an additional argument to pass to valgrind itself.

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.

Track the wall time individual tests take to execute and includes the results in
the summary output. This is useful for determining which tests in a test suite
take the most time to execute. Note that this option is most useful with -j 1.


Run at most N tests and then terminate.

Spend at most N seconds (approximately) running tests and then terminate.

Run the tests in a random order.


Run lit in debug mode, for debugging configuration issues and lit itself.

List the discovered test suites and exit.

List all of the discovered tests and exit.


lit will exit with an exit code of 1 if there are any FAIL or XPASS results. 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).


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.

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.

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.

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.


Each test ultimately produces one of the following six results:

The test succeeded.

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.

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).

The test failed.

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.

The test is not supported in this environment. This is used by test formats which can
report unsupported tests.

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.


This section describes the lit testing architecture for users interested in creating a new
lit testing implementation, or extending an existing one.

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.

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:

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.

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

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.

suffixes For lit test formats which scan directories for tests, this variable is a list
of suffixes to identify test files. Used by: ShTest.

substitutions For lit test formats which substitute variables into a test script, the
list of substitutions to perform. Used by: ShTest.

unsupported Mark an unsupported directory, all tests within it will be reported as
unsupported. Used by: ShTest.

parent The parent configuration, this is the config object for the directory containing
the test suite, or None.

root The root configuration. This is the top-most lit configuration in the project.

pipefail Normally a test using a shell pipe fails if any of the commands on the pipe
fail. If this is not desired, setting this variable to false makes the test fail only
if the last command in the pipe fails.

Once test suites are located, lit recursively traverses the source directory (following
test_source_root) looking for tests. When lit enters a sub-directory, it first checks to
see if a nested test suite is defined in that directory. If so, it loads that test suite
recursively, otherwise it instantiates a local test config for the directory (see LOCAL

Tests are identified by the test suite they are contained within, and the relative path
inside that suite. Note that the relative path may not refer to an actual file on disk;
some test formats (such as GoogleTest) define "virtual tests" which have a path that
contains both the path to the actual test file and a subpath to identify the virtual test.

When lit loads a subdirectory in a test suite, it instantiates a local test configuration
by cloning the configuration for the parent directory --- the root of this configuration
chain will always be a test suite. Once the test configuration is cloned lit checks for a
lit.local.cfg file in the subdirectory. If present, this file will be loaded and can be
used to specialize the configuration for each individual directory. 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

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). 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.

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.

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

<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.

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)

The lit distribution contains several example implementations of test suites in the
ExampleTests directory.

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