Coverage that lives inside your editor

Screenshot pending — add assets/img/hero.png (see SCREENSHOTS.md).

When an AI wrote the tests

A generated test suite looks thorough. Coverage tells you whether it is.

A language model will write you a test suite in seconds, and it will read convincingly. What it cannot tell you is whether those tests reach anything that matters — and neither can line coverage, because a test with no assertions at all still lights up every line it touches.

None of this proves a test is good — nothing can. It tells you, precisely and per line, what was never run: the part a reviewer cannot hold in their head and an assistant will not volunteer. Works with TypeScript and JavaScript through Vitest, Jest or nyc, and with C, C++, Java and Ruby through the tracefiles those toolchains already emit.

Why it's different

One model, every format, zero custom viewer

Up and running in 30 seconds

1. Install the extension and open your project.
2. Run your tests — Command Palette → Fucini Coverage: Run Tests with Coverage. It recognises vitest, jest, pytest, go, cargo, dotnet, maven, gradle, phpunit and ctest, runs your tests with coverage on and loads what they write. Already have a tracefile? Fucini Coverage: Pick Coverage File loads it and remembers it.
3. Open a source file — the gutter shows which lines ran, the status bar the file’s percentage, a hover each line’s hit count, and the run is in the Coverage view and in VS Code’s own Test Coverage panel. From then on it reloads by itself whenever the tracefile changes.

How it compares

VS Code itself and several free extensions show coverage too. This is what each one’s own documentation says it does, as of September 2026 — where a README does not mention something, the table says so rather than guessing.

It is not either/or with VS Code’s own view: every load is published to the native Test Coverage panel as well, filter by test included. Something here out of date? Say so on the contact page.

Supported formats