Local tests run directly on devices-under-test (DUTs) and are similar in function to Autotest's “client” tests. They can do anything that any other code running locally as root can do. Most tests should be local tests.
Remote tests run on the machine initiating testing (e.g. a developer‘s workstation) and run shell commands on the DUT remotely, allowing the DUT to be rebooted in the course of a single test. They are similar in function to Autotest’s “server” tests. They run more slowly than local tests, are harder to write, and are more susceptible to infrastructure and hardware issues.
tast commandThe tast executable is built for the host system by the chromeos-base/tast-cmd package. The developer runs it within their chroot to:
The Running Tests document contains more information about using the tast command.
Test executables (local_tests and remote_tests) consist of compiled tests, along with code for running them and reporting results back to tast. Local tests can be included in a system image via the chromeos-base/tast-local-tests package, while remote tests can be installed onto the host system via the chromeos-base/tast-remote-tests package. Either type of test can also be compiled (and deployed, in the case of local tests) on-the-fly by tast.
Tests don‘t (currently) require anything special from the OS -- tast just needs SSH access to the DUT and (when deploying local tests that aren’t built into the system image) a writable partition that isn't mounted noexec.
See the Writing Tests document for more information.
Tests can be cross-compiled within the chroot by the tast executable using the Go toolchain. Object files are cached and reused where possible -- caching happens at the package level, and tests are grouped into packages by category, e.g. ui, power, security, etc.
For local tests, tast establishes a single SSH connection to the DUT for all communication. The connection is used to copy local_tests and associated test data files to the DUT (if not built into the system image), execute local_tests, and receive the results (including system logs or output data written by the tests).
For remote tests, tast runs remote_tests directly and receives results provided by it. remote_tests establishes SSH connections to the DUT and passes them to tests.