tree: 4cf0c4b5140aad41b5fe85ab90fb8a46fb1e8803 [path history] [tgz]
  1. build/
  2. examples/
  3. plasa/
  4. release/
  5. test_realm/
  6. tests/

Compatibility Test Suite

This directory contains the Fuchsia Compatibility Test Suite (CTS). The Fuchsia CTS is a set of tests designed to provide coverage for Application Programming Interface (API) and Application Binary Interface (ABI) elements (e.g., headers, FIDL files) made available to developers via a Fuchsia SDK. It was originally proposed as RFC 0015.

To learn more, see our documentation on See //sdk/cts/examples for some examples, or peruse the complete set of tests under //sdk/cts/tests.

//sdk/cts Directory structure

A brief rundown of the //sdk/cts directory layout:

  • build/: CTS-specific build rules and scripts.
  • canary/: Files that allow us to modify the CTS tests running in the canary release.
  • data/: Location of static metadata that will be packaged alongside the tests in each CTS release.
  • examples/: Example test cases running in the CTS.
  • plasa/: Build rules, scripts and config files for generating the Platform Surface Area (PlaSA) definition files.
  • release/: Files that allow us to modify the CTS tests running in main CTS releases. Also includes scripts for validating any given CTS release.
  • tests/: Location of the tests in this Compatibility Test Suite.
  • util/: Binaries and utilities needed to run individual end-to-end CTS tests.

Contributing tests

See the CTS Contributing Guide.

Running example tests

To run example tests:

fx set core.qemu-64 --with //sdk/cts/examples/
fx test //sdk/cts/examples/


Target-side tests

Tests for particular headers must be written in a language that supports that header. C headers currently target C11 and C++11 and above. C++ headers currently target C++14 and above. This policy may change as we build a larger test corpus and decide how to enforce C++14 compatibility.

All tests that target API should be written in a language that is supported for end developers per the Fuchsia language policy. The CTS currently only provides direct support for C++ for tests that target API.

Tests that are only intended to exercise ABI may be written in any language supported for use in the Fuchsia Platform Source Tree, including Rust. This may, for example, include tests that check startup handles or the format of the VDSO.

For the most part, tests that exercise FIDL definitions and other APIs shipped with SDKs are API tests that should be written in C++. However, if this places an undue burden on test authorship (e.g., there are large frameworks needed for the test or a substantial body of appropriate existing tests that are written in Rust), we can make exceptions. Note the following:

  • If you do not use C++, your API will not undergo build time compatibility testing. This places a burden on anyone trying to deploy an SDK, because changes to your API are more likely to break compilation of petal code.

  • If there are large test frameworks or libraries that you need to use to write tests for public APIs, and they are only written in a language that is not officially supported for SDK users (see the Fuchsia language policy doc), that means that there is a form of testing that you need for exercising developer use cases that you are not providing to developers. Consider whether those test frameworks should be provided in a language that is supported for end-developers.

  • There will be a high bar for language exceptions for teams that wish to use other languages only because of unfamiliarity with C++. We encourage API developers to understand how end-developers use their APIs.

For information about exceptions to the C++-only policy, file a bug in the CTS bug component.

Host-side tests

For end-to-end tests and scripts that run on the host, we support the use of Dart (and, specifically sl4f).


Since tests are designed to exercise the SDK APIs and ABIs, dependencies on SDK elements (tools, APIs) are allowed.

See the section on build support for information on including new dependencies on first-party code.

In order to avoid relying on third party use of the SDK to test the SDK, CTS tests that run on-device do not rely on third party frameworks that rely on the SDK to build. This is why we use zxtest instead of gtest. If you want to include a third party dependency, file a bug in the CTS bug component to reach out to the team to discuss it.

Code that runs on the host does not have this restriction.