Add native JavaScript coverage for browser runtime by aallan · Pull Request #343 · aallan/vera

aallan · 2026-03-24T23:11:35Z

Summary

Collect V8 coverage from browser parity tests using NODE_V8_COVERAGE env var
Convert to LCOV via npx c8 report and upload to Codecov with javascript flag
Add codecov.yml with python/javascript flags and carryforward: true
Add tests/conftest.py with opt-in local JS coverage (VERA_JS_COVERAGE=1)
Zero changes to test_browser.py — coverage is collected via env var inheritance

How it works

Node.js writes V8 coverage JSON for every node process when NODE_V8_COVERAGE is set. Since _run_node() calls subprocess.run() without env=, child processes inherit the parent environment automatically. Each subprocess writes uniquely-named coverage files. After all tests, npx c8 report merges them into a single LCOV file.

Local usage

VERA_JS_COVERAGE=1 pytest tests/test_browser.py -v -s

Current JS coverage baseline

File	Stmts	Branch	Funcs	Lines
harness.mjs	93.26%	86.66%	100%	93.26%
runtime.mjs	63.52%	65.6%	53.65%	63.52%

Closes #337

Test plan

All 21 pre-commit hooks pass
VERA_JS_COVERAGE=1 pytest tests/test_browser.py -v -s prints JS coverage table
python scripts/check_doc_counts.py passes
CI passes
Codecov shows JS coverage on this PR

🤖 Generated with Claude Code

Summary by CodeRabbit

Chores
- CI now collects and uploads separate JavaScript coverage alongside Python coverage; coverage uploads carry language-specific flags.
- Added ignores for Node.js coverage artifacts.
Tests
- Browser tests can be run with an environment flag to produce JS coverage; test session now prepares and summarises V8 coverage when enabled.
Documentation
- Updated testing and contribution guides with instructions for generating and reporting JavaScript coverage.

Use V8 built-in NODE_V8_COVERAGE to collect JS coverage during browser parity tests. After tests complete, npx c8 converts the accumulated V8 data to LCOV and uploads to Codecov with a javascript flag. Zero changes to test_browser.py — coverage is collected automatically via environment variable inheritance. - CI: Add coverage steps to browser-parity job - codecov.yml: Configure python/javascript flags with carryforward - conftest.py: Opt-in local JS coverage via VERA_JS_COVERAGE=1 - .gitignore: Add node_modules/ and .c8_output/ - Docs: Update TESTING.md, CLAUDE.md, CONTRIBUTING.md Closes #337 Co-Authored-By: Claude <noreply@anthropic.invalid>

coderabbitai · 2026-03-24T23:11:53Z

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 8d706cd and 8a2d048.

📒 Files selected for processing (1)

tests/conftest.py

📝 Walkthrough

Walkthrough

Adds V8/Node JavaScript coverage for browser parity tests: test harness writes V8 coverage, CI generates LCOV via c8 and uploads it to Codecov under a javascript flag, and local pytest support conditionally collects and reports V8 coverage.

Changes

Cohort / File(s)	Summary
CI and Coverage Workflow `\.github/workflows/ci.yml`	Set `NODE_V8_COVERAGE` for browser parity step, generate LCOV from V8 coverage with `npx c8`, upload `js-coverage/lcov.info` to Codecov with `flags: javascript`. Also added `flags: python` to Python upload.
Test Infrastructure `tests/conftest.py`	New session-scoped autouse fixture `_js_coverage_dir` that creates a `v8-coverage` temp dir when `VERA_JS_COVERAGE` is set, exports `NODE_V8_COVERAGE` for subprocesses, and runs `npx c8 report --reporter=text` post-session if data exists.
Coverage Configuration `codecov.yml`	New config declaring separate coverage targets/flags for `python` (paths under `vera/`) and `javascript` (paths under `vera/browser/`), with `carryforward: true` and patch checks set informational.
Documentation & Developer Guidance `CLAUDE.md`, `CONTRIBUTING.md`, `TESTING.md`	Documented running browser tests with `VERA_JS_COVERAGE=1` and CI behaviour for collecting V8 coverage; clarified which changes (e.g. `vera/browser/runtime.mjs`) should include JS coverage.
Version Control `\.gitignore`	Added `node_modules/` and `.c8_output/` to ignore list to avoid checking in Node deps and c8 artefacts.

Sequence Diagram(s)

mermaid
sequenceDiagram
autonumber
participant CI as CI Runner
participant Py as pytest
participant Node as Node/c8
participant Codecov as Codecov
CI->>Py: run pytest tests/test_browser.py with VERA_JS_COVERAGE=1
Py->>Node: spawn harness (inherits NODE_V8_COVERAGE)
Node->>Node: write raw V8 coverage files to temp dir
CI->>Node: npx c8 report --reporter=lcov --report-dir=./js-coverage --temp-directory=<tmp>
Node-->>CI: produce js-coverage/lcov.info
CI->>Codecov: upload js-coverage/lcov.info with flags: javascript
CI->>Codecov: upload Python coverage with flags: python

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Suggested labels

ci, docs, tests

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately and specifically summarises the main change: adding JavaScript coverage collection for the browser runtime via V8.
Linked Issues check	✅ Passed	All primary objectives from issue `#337` are met: V8 coverage collection via NODE_V8_COVERAGE, LCOV conversion via c8, Codecov upload with javascript flag, and optional local JS coverage opt-in.
Out of Scope Changes check	✅ Passed	All changes are in scope: CI workflow updates, coverage configuration, test fixtures, and documentation additions directly support the JavaScript coverage implementation objective.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

📝 Generate docstrings

Create stacked PR
Commit on current branch

🧪 Generate unit tests (beta)

Create PR with unit tests
Commit unit tests in branch feat/js-coverage

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codecov · 2026-03-24T23:12:50Z

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.96%. Comparing base (ce1c110) to head (8a2d048).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #343      +/-   ##
==========================================
- Coverage   95.37%   91.96%   -3.42%     
==========================================
  Files          45       47       +2     
  Lines       16141    17849    +1708     
  Branches        0      211     +211     
==========================================
+ Hits        15395    16415    +1020     
- Misses        746     1430     +684     
- Partials        0        4       +4

Flag	Coverage Δ
javascript	`59.71% <ø> (?)`
python	`95.37% <ø> (?)`

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

Split project/patch status into per-flag checks so JS coverage (63%) does not drag down the Python metric (95%). Mark JS checks as informational until the baseline stabilises. Co-Authored-By: Claude <noreply@anthropic.invalid>

aallan · 2026-03-24T23:19:31Z

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coderabbitai · 2026-03-24T23:19:47Z

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aallan · 2026-03-24T23:20:08Z

@coderabbitai full review

coderabbitai · 2026-03-24T23:20:14Z

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Full review triggered.

coderabbitai

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@tests/conftest.py`:
- Around line 34-44: The subprocess.run call that invokes "npx c8 report" in the
teardown currently has no timeout and can hang; update the teardown to call
subprocess.run([...], check=False, timeout=<reasonable_seconds>) and catch
subprocess.TimeoutExpired around that call (referencing subprocess.run and the
"npx c8 report" invocation and cov_dir) so the test suite won’t block — on
timeout log or print a concise warning and continue/cleanup instead of letting
pytest hang.

ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro

Run ID: e2e11afe-ff49-441f-9634-011ae1d8859b

📥 Commits

Reviewing files that changed from the base of the PR and between ce1c110 and 8d706cd.

📒 Files selected for processing (7)

.github/workflows/ci.yml
.gitignore
CLAUDE.md
CONTRIBUTING.md
TESTING.md
codecov.yml
tests/conftest.py

Co-Authored-By: Claude <noreply@anthropic.invalid>

aallan · 2026-03-24T23:43:50Z

The JS coverage setup uses a clever pattern: V8's built-in coverage (via NODE_V8_COVERAGE env var) collects raw coverage data during normal Node.js execution — no instrumentation or source transforms needed. c8 then converts this into lcov format that Codecov understands. The codecov.yml flags system means Python and JS coverage are evaluated independently, so a 63% JS score won't block PRs that only touch Python code.

Fix Codecov: separate Python and JS coverage checks

8d706cd

Split project/patch status into per-flag checks so JS coverage (63%) does not drag down the Python metric (95%). Mark JS checks as informational until the baseline stabilises. Co-Authored-By: Claude <noreply@anthropic.invalid>

coderabbitai Bot reviewed Mar 24, 2026

View reviewed changes

Comment thread tests/conftest.py Outdated

Add 120s timeout to c8 report in conftest fixture

8a2d048

Co-Authored-By: Claude <noreply@anthropic.invalid>

aallan merged commit 4daac70 into main Mar 24, 2026
17 checks passed

aallan deleted the feat/js-coverage branch March 24, 2026 23:42

aallan mentioned this pull request Mar 25, 2026

Improve browser runtime (runtime.mjs) test coverage to >80% #349

Open

coderabbitai Bot mentioned this pull request Mar 30, 2026

fix: remove closed issues #337 and #226 from ROADMAP and limitation tables #437

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Add native JavaScript coverage for browser runtime#343

Add native JavaScript coverage for browser runtime#343
aallan merged 3 commits into
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