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lit - LLVM Integrated Tester
:program:`lit` [options] [tests]
:program:`lit` is a portable tool for executing LLVM and Clang style test suites, summarizing their results, and providing indication of failures. :program:`lit` is designed to be a lightweight testing tool with as simple a user interface as possible.
Each specified test will be executed (potentially in parallel) and once all tests have been run :program:`lit` will print summary information on the number of tests which passed or failed (see :ref:`test-status-results`). The :program:`lit` program will execute with a non-zero exit code if any tests fail.
By default :program:`lit` will use a succinct progress display and will only print summary information for test failures. See :ref:`output-options` for options controlling the :program:`lit` progress display and output.
:program:`lit` also includes a number of options for controlling how tests are executed (specific features may depend on the particular test format). See :ref:`execution-options` for more information.
:program:`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 :program:`lit` can be either individual tests, or entire directories or hierarchies of tests to run. When :program:`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 :program:`lit` model, every test must exist inside some test suite. :program:`lit` resolves the inputs specified on the command line to test suites by searching upwards from the input path until it finds a :file:`lit.cfg` or :file:`lit.site.cfg` file. These files serve as both a marker of test suites and as configuration files which :program:`lit` loads in order to understand how to find and run the tests inside the test suite.
Once :program:`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, :program:`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 :program:`lit` to provide convenient and flexible support for out-of-tree builds.
TEST STATUS RESULTS
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 :ref:`output-options` section for more information.
:program:`lit` proper is primarily an infrastructure for discovering and running arbitrary tests, and to expose a single convenient interface to these tests. :program:`lit` itself doesn't know how to run tests, rather this logic is defined by test suites.
As described in :ref:`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.
:program:`lit` identifies test suites as directories containing lit.cfg or lit.site.cfg files (see also :option:`--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 :option:`--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_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 :program:`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.
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, :program:`lit` recursively traverses the source directory (following test_source_root) looking for tests. When :program:`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 :ref:`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.
LOCAL CONFIGURATION FILES
When :program:`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 :program:`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.
TEST RUN OUTPUT FORMAT
The :program:`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:
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:
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:
LIT EXAMPLE TESTS
The :program:`lit` distribution contains several example implementations of test suites in the ExampleTests directory.