Contributing Tests to CTF

This guide explains how to add and remove CTF tests.

How to add a test to CTF

Please read the CTF test requirements before getting started. The most notable requirement is that a test must use a test realm factory before this guide can be followed.

A test is included in CTF if it is in the group at //sdk/ctf/tests:tests. Before adding the test to this group, it's build rules must be rewritten to use CTF versions. This is an unfortunate but necessary step that will go away soon.

To add a test to this group, perform each of the steps below in the file containing the test's fuchsia_test_component target.

1. Import CTF build rules


2. Use CTF GN templates

Replace the test's fuchsia_package declaration with ctf_fuchsia_package:


fuchsia_package("fuchsia-example-tests") {
  testonly = true
  package_name = "fuchsia-example-tests"
  deps = [ ":fuchsia-example-test-component" ]


ctf_fuchsia_package("fuchsia-example-tests") {
  testonly = true
  package_name = "fuchsia-example-tests"
  deps = [ ":fuchsia-example-test-component" ]

3. Add the test release archive to the build graph

ctf_fuchsia_package generates a ${target_name}_archive target that produces a FAR archive of the test. This archive is what gets released in CTF. Add a group("tests") target to the file if it doesn't exist, then add the archive as a dependency:

group("tests") {
  testonly = true
  deps = [

You successfully added a group("tests") to the file. You are now ready to add that group to //sdk/ctf/tests:tests.

4. Add a GN template to build the prebuilt CTF test

To teach CTF how to build the test's prebuilt package into a runnable target, create a GN template that generates a package identical to the fuchsia_test_package used to run the latest version of the test. For example, if the test root component and test package look like this:

fuchsia_test_component("fuchsia-example-test-root") {
  testonly = true
  manifest = "meta/fuchsia-example-test-root.cml"
  test_type = "ctf"

fuchsia_test_package("fuchsia-example-tests-latest") {
  test_components = [ ":fuchsia-example-test-root" ]
  subpackages = [
    ":fuchsia-example-tests", # latest version of the test suite.
  deps = [ ":fuchsia-example-test-helper" ]

Then add this template to //sdk/ctf/build/generate_ctf_tests.gni

template("generate_fuchsia-example-tests") {
  forward_variables_from(invoker, [ "test_info" ])
  fuchsia_package_with_test(target_name) {
    test_component = "//path/to/test:fuchsia-example-test-root",
    test_component_name = ""
    subpackages = [
      test_info.target_label, # prebuilt version of the test suite.
    deps = [ "//path/to/test:fuchsia-example-test-helper" ]
  • For CTF to match this template with the prebuilt test package, this template must be named as generate_{package_name} and package_name must match the test's original ctf_fuchsia_package name.
  • This template subpackages test_info.target_label instead of :fuchsia-example-tests because the former points to the prebuilt version of the test from CIPD and the latter points to the latest version built from source.

5. Test the changes

To verify that these steps were completed correctly, run these commands:

fx set core.x64 --with //sdk/ctf:ctf_artifacts
fx build

The build should show an error prompt to run a command that updates //sdk/ctf/goldens/package_archives.json. Run that command, then run fx build again.

At this stage the build will print an error if the GN template defined in the previous step is missing or if it cannot match the prebuilt version of the test with the GN template. If everything succeeds, the test can be run using this command:

fx test fuchsia-example-test_ctf<N>

Given that this is the version of the prebuilt test from the current build rather than some version from a previous CTF release, N is the Fuchsia platform's currently in-development API level.

6. Submit the changes

Send the changes for review. After submission the test will automatically be included in the next CTF release when the next milestone branch is cut. For additional review, please reach out to

How to remove a test from CTF

To remove a test from future CTF releases:

  1. Remove the test archive from the build graph.
  2. Delete the test's gn template.
  3. Remove the ctf templates from the test's build rules.

Submit these changes to the main branch. Over time all of the API levels corresponding to each release will become unsupported and the last version of the test will stop running in CQ.

If you must immediately remove a test and all of its prebuilt version from CQ, as an additional step you should follow Fuchsia's change control process and cherry pick a CL that removes the test from the each of the corresponding release branches. For example, If you want to remove a test from the CTF release for API level 20, your CL needs to be cherry picked onto the releases/f20 branch.

Test requirements

Every test must meet these requirements before being added to CTF.

CTF tests must use the test realm factory pattern

The test realm factory pattern allows the build to version the test suite component in CTF without versioning the component(s) under test. Please read the test realm factory guide and refactor the test if necessary before following this guide.

CTF tests must only depend on partner-facing ABIs

A CTF test must only depend on software in the partner SDK category at runtime because the test will force its dependencies to remain stable. This is not enforced by presubmit checks. Usually test authors just need to verify that the FIDL protocols their test suite components use are all available in the partner SDK category.

CTF tests must be written in C, C++, or Rust

At the time of writing CTF only supports these languages.