[huntie]

Summary

The C++ unit tests under packages/react-native/ReactCommon/**/tests run only inside Meta, under Buck. Public CI has no build for them, so a change that breaks one passes every GitHub check and fails only after import, as happened with #59686.

This adds a test_react_common_cxx job to Test All that builds and runs them on Linux, reusing the Fantom tester's CMake build, which already compiles every ReactCommon library with folly, Hermes and codegen.

Changes

• Add private/react-native-fantom/tester/react-common-tests/: one GoogleTest executable per tests directory (38 today), linked against the libraries fantom_tester links. Each test case is registered with CTest through gtest_discover_tests, so it runs in its own process.
• Add :private:react-native-fantom:testReactCommon, which builds them and runs ctest. GoogleTest 1.18.0 is downloaded like the Fantom tester's other dependencies.
• Add the test_react_common_cxx job to test-all.yml, mirroring build_fantom_runner on the same container and runner. It adds no ccache steps: in this container compiles do not go through ccache, and build_fantom_runner on main reports 0 hits and 0 misses.

Notes

• NOTE: Three Hermes debugger cases in jsinspector-modern/tests fail in OSS on macOS and Linux alike, and are excluded by name in the CMake file (see Test Plan).
• The job installs clang 18 from apt.llvm.org, since the tests use C++20 features the image's clang 14 lacks: std::source_location and parenthesised aggregate initialisation.
• Each case runs in its own process because some suites leave global state behind. In jsinspector-modern/tests, TracingTest fails when run after the other suites in one process, and passes on its own.
• The tests compile with -Wno-error, since the header-only ReactCommon libraries export -Werror -Wpedantic and a few tests call deprecated APIs.
• benchmarks/ directories are left out, as they need Google Benchmark.

Changelog: [Internal]

Test Plan

On macOS (Apple clang 21, CMake 3.30.5 from the Android SDK, JDK 17):

yarn install
./gradlew :private:react-native-fantom:testReactCommon

All 38 test executables build, and 1522 test cases pass, one of which skips itself (ReactInstanceTest.testRegistersRuntimeSchedulerAsEventLoopControl: this Hermes build has no ISetEventLoopControl).

Before the exclusions, 1525 cases ran and these 3 failed, with the same result on macOS and in this job on Linux:

• JsiIntegrationHermesTest.ResolveColumnlessBreakpointAfterEval: Debugger.setBreakpointByUrl returns no locations.
• JsiIntegrationHermesTest.ResolveColumnlessBreakpointAfterReload: the same.
• JsiIntegrationHermesTest.TwoConnectionsDebuggerLifecycle: the second session gets no Debugger.scriptParsed after the first disables Debugger.

test_react_common_cxx on this PR: passed in 14m15s, with all 1522 tests passing. Running them takes 30 seconds of that; the rest is the build.

[cortinico]

Code looks great ✅

[cipolleschi]

can we have a reusable workflow rather than a reusable action? It's much easier to maintain. Also, if it is only used in test-all, can we just put the workflow there instead of splitting it in two places?

[huntie]

Yeah it's semantically part of test-all, which is getting long at this point. For now I'll move this inline so we have less files to look at, at least (although I believe reusable actions are a fair pattern). The scope of this test suite is a single job in this workflow, IMO.

I'm certainly keen, after this, that we do another pass over all GHA files to simplify. But that goes beyond the initial scope here.

[meta-codesync]

@cortinico has imported this pull request. If you are a Meta employee, you can view this in D129898681.

[huntie]

@cipolleschi Can I get signal on what is failing internally here?

[vzaidman]

@huntie

Seems like an internal issue. We have a few issues going on now. I'll let you know in a moment. I'm rebasing the PR.

EDIT: seems to be landing now.

[react-native-bot]

This pull request was successfully merged by @huntie in 6990b94

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