Tast: Running Tests (go/tast-running)

Basic syntax

Tests can be executed within a Chrome OS chroot using the tast executable's run command:

tast run <target> <test-pattern> <test-pattern> ...

To run private tests (e.g. crosint test bundle), use -buildbundle=<bundle-name>.

Specifying where to run tests

The first positional argument supplied to the run subcommand specifies the “target”, i.e. the device where the test will be run, also known as the device-under-test or DUT. In the case of local tests, the test code will run directly on the DUT. For remote tests, the test code will run on the host machine but connect to the DUT. Expressions like root@, root@localhost, and are supported. The root user is used by default, as tests frequently require root access to the DUT.

By default, the standard testing_rsa key from chromite/ssh_keys will be used to establish an SSH connection with the device. The keyfile flag can be supplied to specify a different private key:

tast run -keyfile=$HOME/.ssh/id_rsa ...

Specifying which tests to run

Any additional positional arguments describe which tests should be executed:

  • If no arguments are supplied, all tests are selected.
  • If a single argument surrounded by parentheses is supplied, it is interpreted as a boolean expression consisting of test attributes. For example, the expression (("dep:chrome" || "dep:android") && !informational) matches all tests with a dep:chrome or dep:android attribute but not an informational attribute. Attributes that don't consist of a letter or underscore followed by letters, digits, and underscores must be double-quoted. ‘*’ characters in quoted strings are interpreted as wildcards. See chromiumos/tast/internal/expr for details about expression syntax.
  • Otherwise, the argument(s) are interpreted as wildcard patterns matching test names. For example, ui.* matches all tests with names prefixed by ui.. Multiple patterns can be supplied: passing example.Pass and example.Fail selects those two tests.
  • It's invalid to mix attribute expressions and wildcard patterns. To use a wildcard to match against the test name you can use the "name:ui.*" expression instead.

See the Test Attributes document for more information about attributes.

Tests may be skipped if they list software dependencies that aren‘t provided by the DUT. This behavior can be controlled via the tast command’s -checktestdeps flag.

Controlling whether tests are rebuilt

When the -build flag is true (the default), tast run rebuilds the cros test bundle and pushes it to the DUT as /usr/local/share/tast/bundles_pushed/cros. This permits faster compilation and deployment when writing new tests than the normal emerge/cros deploy cycle can provide.

The name of the bundle to build, push, and run can be specified via the -buildbundle flag. If the bundle‘s source code is outside of the tast-tests repository, you will need to specify the repository’s path using the -buildtestdir flag.

To rebuild a test bundle, the tast command needs its dependencies' source code to be available. This code is automatically checked out to /usr/lib/gopath when building packages for the host system, as described in the Go in Chromium OS document. The tast command will automatically inform you when the bundle's dependencies need to be manually emerged.

To skip rebuilding a bundle and instead run all builtin bundles within the /usr/local/share/tast/bundles directory on the DUT (for local tests) and /usr/share/tast/bundles on the host system (for remote tests), pass -build=false. The default builtin cros local bundle should be present on all test system images (non-test system images are not supposed by Tast).

Interpreting test results

As each test runs, its output is streamed to the tast executable. Overall information about the current state of the test run is logged to stdout by default. The top-level (i.e. tast -verbose run ...) -verbose flag can be supplied to log additional information to the console, including all messages written by tests.

By default, test results are written to a subdirectory under /tmp/tast/results, but an alternate directory can be supplied via the run command's -resultsdir flag. If the default directory is used, a symlink will also be created to it at /tmp/tast/results/latest.

Various files and directories are created within the results directory:

  • crashes/ - Breakpad minidump files with information about crashes that occured during testing.
  • full.txt - All output from the run, including messages logged by individual tests.
  • results.json - Machine-parseable test results, supplied as a JSON-marshaled array of run.TestResult structs.
  • run_error.txt - Error message describing the reason why the run was aborted (e.g. SSH connection to DUT was lost). Only written when a global error occurs.
  • streamed_results.jsonl - Streamed machine-parseable test results, supplied as a JSONL array of run.TestResult structs. Provides partial results if the tast process is interrupted before results.json is written.
  • system_logs/ - Diff of /var/log on the DUT before and after testing.
    • unified/ - Unified log collected from system logs.
      • unified.log - Human-readable system log messages.
      • unified.export.gz - gzip-compressed logs with full metadata from croslog's export mode which is similler to journalctl -o export.
  • tests/<test-name>/ - Per-test subdirectories, containing test logs and other output files.
    • log.txt - Log of messages and errors reported by the test.
    • (optional) results-chart.json - Machine-parseable performance metrics produced by the perf package.
    • ... - Other output files from the test.
  • timing.json - Machine-parsable JSON-marshaled timing information about the test run produced by the timing package.

Reset the device owner of the DUT after test run

Tast resets the device owner of the DUT before test run, and after the test run, the device owner remains to be testuser. To reset that, run the following on the DUT:

stop ui
rm -rf /var/lib/whitelist '/home/chronos/Local State'
start ui