devtools-verification

# Instructions on how to verify your changes ## Testing - To test a file, you can run `npm run test -- <FILEPATH>` where `FILEPATH` is a path to a `*.test.ts` file, relative to the working directory. - Test files are usually defined alongside their implementation. So if you are working on `front_end/panels/timeline/TimelinePanel.ts`, you would expect the test file to be defined in `front_end/panels/timeline/TimelinePanel.test.ts`. - You can also test an entire directory. For example, `npm run test -- front_end/models/trace` will run all tests in that directory. ## Building & compiling - Check for build issues by running `autoninja -C out/Default`. ## Linting - `npm run lint` will execute ESLint and StyleLint. It will report any violations and automatically fix them where possible. - To run the linter on a specific file or directory, you can run `npm run lint -- <PATH>` where `PATH` is a path to a file or directory. This will also automatically fix violations where possible. ## Fetching Tryjob Results, Failure Logs, & Screenshot Goldens Use `scripts/tools/get_cl_test_results.py` to fetch all tryjob build statuses, per-test failure logs, Blink web test text diffs, and screenshot artifacts (`actual_image`, `expected_image`, `image_diff`) for a CL in one command: ```bash # Fetch all build statuses, failure logs, and artifacts for a CL into an output directory: scripts/tools/get_cl_test_results.py --cl <CL_NUMBER> --output-dir <OUTPUT_DIR> # Filter for specific failing tests (e.g. DOMTreeWidget) or specific builders: scripts/tools/get_cl_test_results.py --cl <CL_NUMBER> --test-filter "DOMTreeWidget" --output-dir <OUTPUT_DIR> # Also apply Linux actual_image screenshot artifacts directly to test/goldens/linux/...: scripts/tools/get_cl_test_results.py --cl <CL_NUMBER> --output-dir <OUTPUT_DIR> --apply-goldens ``` ### Screenshot Golden & Inspection Rules - **Linux-only goldens**: Never generate, update, or commit golden PNGs from macOS. Screenshot tests in DevTools only use Linux goldens (`test/goldens/linux/...`) produced by Linux trybots (`dtf_linux_rel` / `dtf_linux_dbg`). Do not run screenshot tests locally on macOS to verify goldens. - **Multimodal inspection only**: Always inspect `actual_image.png`, `expected_image.png`, and `image_diff.png` directly using your multimodal file viewer (`view_file`). Never write or run programmatic image comparison scripts. ## Best practices - Run tests often to verify your changes. - Prefer using a fast build, if it exists, to keep the feedback loop shorter. - Periodically build to check for errors. - Run `git cl presubmit -u` at the end of your code changes.