host_target_interaction_tests.md

Host-target interaction tests

For the purposes of this doc "target" is the machine running a version of Fuchsia being tested, and "host" is the machine running some stable OS. A host-target interaction test runs on the host and interacts with the target.

Declaration in GN

To declare a host-target interaction test in GN:

1. Declare a test executable.
2. Specify one or more environments that include Fuchsia (target) devices.
3. Add a dependency between a tests bundle and the test executable, specifying host_toolchain.

For example:

# Doesn't have to be go_test. This is just an example.
go_test("an_hti_test") {
    ...
    # Declares that Fuchsia should be running in an emulator before this test
    # starts on the host.
    environments = [emu_env]
    ...
}

# This should be included in the transitive deps of some tests bundle.
group("tests") {
    testonly = true
    # Anything that depends on ":tests" will build the test as a host test.
    public_deps = [":an_hti_test($host_toolchain)"]
}

Host test API

The continuous integration infrastructure (AKA "infra") and fx test start the target and then invoke the test on the host.

SL4F is one way for the host to interact with the target. The SL4F host libraries take responsibility for establishing a connection with the target.

Tests that don't want to use SL4F can parse these environment variables and handle their own communication with the host:

• FUCHSIA_IPV4_ADDR: IPv4 address.
• FUCHSIA_IPV6_ADDR: IPv6 address.
• FUCHSIA_SSH_KEY: SSH key file path.