Fucini Coverage Studio Pro

Native VS Code coverage for lcov, llvm-cov JSON, Cobertura, JaCoCo, Istanbul/nyc and SimpleCov. Gutters, the built-in Test Coverage panel, per-function CodeLens, branch & MC/DC hover, diff coverage, a composite safety-weighted score, and self-hosted HTML reports — wired straight into VS Code's own coverage UI. No separate viewer, no webview report to babysit.

By Mario Fucini — Fucini Consulting

Full documentation: User Guide · Notice · License · Contact

Evaluation release. This is a time-limited evaluation build: it runs free through 2026-12-31. After that, run Fucini Coverage: Show License / Activation and request a key — it's issued and applied automatically after a short evaluation questionnaire (just usage/wishes questions on a renewal) so we can improve the extension. If that ever fails, send the request code shown there via the Contact page or info@fucini.consulting instead.

Requirements

VS Code ≥ 1.88 (for the native Test Coverage API).
A coverage tracefile your project already produces — see Supported formats below.

Quick start

Generate a coverage tracefile with your normal test workflow.
Command Palette → Fucini Coverage: Load Coverage (or leave fuciniCoverage.watch.enabled on — the default — and it loads automatically once a matching file appears).
Open a covered source file: covered lines get a green gutter with an inline hit count, uncovered lines get red, and the Test Coverage panel opens in the sidebar.

Supported formats

Format	Typical file
LCOV	`lcov.info`, `*.info`
llvm-cov JSON	`llvm-cov export --format=json` output
Cobertura XML	`coverage.xml`
JaCoCo XML	`jacoco.xml`
Istanbul / nyc	`coverage-final.json`
SimpleCov (Ruby)	`.resultset.json`, `coverage.json` (`simplecov-json` gem)

Multiple tracefiles are merged deterministically into one run with recorded provenance, regardless of load order.

Features

Core

Native gutters, overview ruler, and Test Coverage panel — no custom webview.
Per-line statement, branch, function, region, MC/DC and C++ instantiation coverage (whatever the tracefile provides).
Multi-format ingestion and deterministic merge of several runs.
Path remapping — CI build-machine paths → your local workspace.
Diff coverage — decorate only lines changed vs a git base ref.
Explorer badges (line % per file/folder; colour = the composite score) and a run-wide status-bar item ($(dashboard) NN%), hover for a full metrics table.
Watch mode — auto-reload when a tracefile changes.

Composite score & compliance

A single Weighted Harmonic Mean score across lines, branches, functions, regions, MC/DC and instantiations, with weights aligned to IEC 61508 / ISO 26262 / DO-178C tiers (fuciniCoverage.whmWeights.*).
COMPLIANT / NON-COMPLIANT verdict driven by per-metric thresholds and a configurable fuciniCoverage.compliance.mode (strict, whm, both, either).

Excluding non-code lines

Comment-only and blank lines are auto-excluded from totals (handles a known llvm-cov/gcov quirk where a stray hit count lands on a comment).
Honors LCOV_EXCL_LINE / LCOV_EXCL_START / LCOV_EXCL_STOP markers.

In-editor analysis

Function CodeLens — per-function coverage %, click to jump to its first uncovered line.
Branch & MC/DC hover — per-arm taken/not-taken counts and per-decision condition/vector breakdowns; optional coloured MC/DC margin gutter.
Dead-code warnings — Problems-panel warning for functions with measurable lines and zero coverage.
Next/Previous Uncovered navigation commands.
Per-file status bar — the active editor's own coverage percentage.

Finding what to test next

Show Worst-Covered Files / Functions — Quick Pick ranked lowest-first.
Copy Uncovered Lines — Markdown summary of every gap, ready to paste into a PR description.

History & reporting

Optional local run history with a coverage trend (▲/▼) in the status bar, plus Compare Two History Runs and Compare with Last Run.
Generate Full HTML Report — a self-rendered, multi-page, per-directory report; Open HTML Report / Open Annotated Source for a single file.
Export Fucini JSON — the full normalised model.
Stale-coverage warning when a source file changed after its run.

Commands

Command Palette (Ctrl+Shift+P) → type Fucini Coverage:

Command	What it does
Load Coverage	Discover & load coverage for the workspace.
Pick Coverage File	Manually choose a tracefile.
Show Loaded Coverage Files	List the tracefiles in the active run.
Toggle Watch	Turn auto-reload on/off.
Next / Previous Uncovered	Jump between uncovered regions.
Open HTML Report	Open the rendered static report.
Generate Full HTML Report	Build the multi-page report.
Open Annotated Source / …to the Side	Annotated coverage view for a file.
Toggle Annotated Source	Swap between source and annotated view.
Show Worst-Covered Files / Functions	Ranked lowest-first Quick Pick.
Copy Uncovered Lines	Markdown summary of every uncovered range.
Compare Two History Runs / Compare with Last Run	Per-file regression diff.
Check Coverage Thresholds	Evaluate the compliance gates.
Export Fucini JSON	Export the current run as Fucini JSON.
Show Status Bar Menu	Open the quick-action menu.

CodeLens, branch/MC-DC hover, dead-code warnings, badges and the status-bar items all work automatically once coverage is loaded.

Settings

Configure in the Settings UI (search Fucini Coverage) or settings.json. Every option, with its default:

Discovery & loading

Setting	Default	What it does
`fuciniCoverage.coverageFile.defaultLocation`	`""`	Base folder for discovery and file-pick dialogs (`${workspaceFolder}` supported).
`fuciniCoverage.coverageFile.paths`	`[]`	Tracefile(s) to load & merge, relative to the base folder. `*` globs recurse.
`fuciniCoverage.watch.enabled`	`true`	Reload coverage when a tracefile changes.

Colour scale & badges

Setting	Default	What it does
`fuciniCoverage.colorScale.lowColor`	`#8b1a1a`	Low end of the coverage gradient.
`fuciniCoverage.colorScale.midColor`	`#b8860b`	Pivot colour of the gradient.
`fuciniCoverage.colorScale.highColor`	`#228b22`	High end (100%) of the gradient.
`fuciniCoverage.colorScale.lowThreshold`	`80`	% at which the badge steps low → mid.
`fuciniCoverage.colorScale.highThreshold`	`90`	% at which the badge steps mid → high (and gradient pivot).

Composite score (Weighted Harmonic Mean)

Setting	Default	What it does
`fuciniCoverage.whmWeights.lines`	`1`	Weight for line/statement coverage.
`fuciniCoverage.whmWeights.functions`	`1`	Weight for function coverage.
`fuciniCoverage.whmWeights.regions`	`1.5`	Weight for region coverage (llvm-cov).
`fuciniCoverage.whmWeights.branches`	`2`	Weight for branch coverage.
`fuciniCoverage.whmWeights.mcdc`	`4`	Weight for MC/DC coverage.
`fuciniCoverage.whmWeights.instantiations`	`0.5`	Weight for C++ template instantiations (llvm-cov).

Thresholds & compliance

Setting	Default	What it does
`fuciniCoverage.threshold.statement`	`100`	Minimum statement %. `0` disables the gate.
`fuciniCoverage.threshold.branch`	`100`	Minimum branch %.
`fuciniCoverage.threshold.mcdc`	`100`	Minimum MC/DC %.
`fuciniCoverage.threshold.functions`	`100`	Minimum function %.
`fuciniCoverage.threshold.regions`	`100`	Minimum region % (llvm-cov).
`fuciniCoverage.threshold.instantiations`	`100`	Minimum instantiation % (llvm-cov).
`fuciniCoverage.threshold.weighted`	`100`	Minimum composite score.
`fuciniCoverage.compliance.mode`	`strict`	`strict` \| `whm` \| `both` \| `either`.

Diff, remap & reports

Setting	Default	What it does
`fuciniCoverage.pathRemap`	`[]`	Ordered `{from,to}` path rewrites.
`fuciniCoverage.gitDiff.enabled`	`false`	Restrict coverage to lines changed vs a base ref.
`fuciniCoverage.gitDiff.baseRef`	`origin/master`	Git base ref for diff coverage.
`fuciniCoverage.externalHtmlReport.dir`	`""`	Read a pre-built `llvm-cov show` HTML dir for Annotated Source.
`fuciniCoverage.htmlReport.outputDir`	`""`	Output dir for Generate Full HTML Report.

Display & analysis

Setting	Default	What it does
`fuciniCoverage.mcdcGutter.enabled`	`false`	Coloured MC/DC margin gutter.
`fuciniCoverage.statusBar.enabled`	`true`	Show run-wide & per-file status-bar items.
`fuciniCoverage.statusBar.showLauncher`	`true`	Always-available quick-menu launcher.
`fuciniCoverage.codeLens.enabled`	`true`	Per-function coverage CodeLens.
`fuciniCoverage.deadCode.enabled`	`true`	Warn on zero-coverage functions.
`fuciniCoverage.staleWarning.enabled`	`true`	Warn when a file changed after its run.
`fuciniCoverage.excludeComments`	`true`	Exclude comment/blank & `LCOV_EXCL_*` lines.
`fuciniCoverage.excluded.includeInTotals`	`false`	Count excluded lines toward totals.

History

Setting	Default	What it does
`fuciniCoverage.history.enabled`	`false`	Store runs locally for trend & comparison.
`fuciniCoverage.history.retention`	`20`	Max stored runs to keep.

Status-bar quick actions

All default false; enable to add the matching action to the quick menu: quickActions.compareWithLastRun, openAnnotatedSource, openAnnotatedSourceToSide, toggleAnnotatedSource, toggleWatch, worstCoveredFiles, worstCoveredFunctions, nextUncovered, previousUncovered, checkThresholds, copyUncoveredLines, compareHistoryRuns, exportJson.

Telemetry

Setting	Default	What it does
`fuciniCoverage.telemetry.enabled`	`true`	Anonymous usage telemetry, on by default for the evaluation trial — turn off at any time. Also gated by VS Code's own `telemetry.telemetryLevel`.

Updates

Setting	Default	What it does
`fuciniCoverage.update.checkForUpdates`	`true`	Periodically check both fucini.software and the VS Code Marketplace for a newer release, and offer to install whichever is newer.

Licensing

Setting	Default	What it does
`fuciniCoverage.license.key`	`""`	Activation key for the evaluation pre-release. Paste the `FCK1.…` key you receive (see the evaluation note at the top). Bound to this machine/user.

See the User Guide for worked examples, path-remapping recipes, CI/CMake integration, and the full FUCINI_* error-code reference.

Privacy

Telemetry is controlled by the telemetry.enabled setting above. It defaults on for the evaluation trial and can be turned off at any time. See its package.json description and NOTICE.

Contact

Questions, bug reports, or alternate licensing terms — contact Fucini Consulting via the contact page or by email at info@fucini.consulting.

License

MIT with an attribution-in-release-notes condition — see LICENSE and NOTICE.