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 information.
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 see “LIT INFRASTRUCTURE”
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.
–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.
Suppress any output except for test failures.
Show less output, for example don’t show information on tests that pass.
Show more information on test failures, for example the entire test output instead of just the test result.
Do not use curses based progress bar.
Specify an addition PATH to use when searching for executables in tests.
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.
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 as part of the standard output.
Run Tcl scripts internally (instead of converting to shell scripts).
Run each test N times. Currently this is primarily useful for timing tests, other results are not collated in any reasonable fashion.
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|”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 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_src_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, TclTest.
substitutions For lit test formats which substitute variables into a test script, the list of substitutions to perform. Used by: ShTest, TclTest.
unsupported Mark an unsupported directory, all tests within it will be reported as unsupported. Used by: ShTest, TclTest.
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.
on_clone The config is actually cloned for every subdirectory inside a test suite, to allow local configuration on a per-directory basis. The on_clone variable can be set to a Python function which will be called whenever a configuration is cloned (for a subdirectory). The function should takes three arguments: (1) the parent configuration, (2) the new configuration (which the on_clone function will generally modify), and (3) the test path to the new directory being scanned.
Once test suites are located, lit recursively traverses the source directory (following test_src_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 CONFIGURATION FILES”).
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 direction – 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 files.
The b<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 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.
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.