# Improving elm-coverage

**URL:** <https://discourse.elm-lang.org/t/improving-elm-coverage/10533>\
**Category:** Show and Tell\
**Created:** [January 26, 2026, 12:33pm UTC](https://discourse.elm-lang.org/t/improving-elm-coverage/10533 "2026-01-26T12:33:24Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![rupert](https://yyz1.discourse-cdn.com/flex035/user_avatar/discourse.elm-lang.org/rupert/32/1775_2.png) [@rupert](https://discourse.elm-lang.org/u/rupert)\
**Post date:** [January 26, 2026, 12:33pm UTC](https://discourse.elm-lang.org/t/improving-elm-coverage/10533/1 "2026-01-26T12:33:24Z")

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[elm-coverage](https://github.com/zwilias/elm-coverage) is a tool that will instrument Elm code and when you run it, output coverage counters and generate an HTML report.

The problem I had with this tool is that it outputs the report into a single large HTML file. Opening this file in the browser for a 200K LOC Elm project is pretty slow. Trying to get AI coding tools to read it is also difficult.

I forked the original and am making some changes here:

> **[GitHub - rupertlssmith/elm-coverage: Explorations](https://github.com/rupertlssmith/elm-coverage)**
>
> Explorations

So far:

- It outputs the HTML report with 1 overall file mapping the whole project, and 1 HTML file per module, in a directory structure that 1:1 reflects the source code.
- You can output a JSON formatted report with `--report json` CLI option.

The JSON formatted report is much smaller and better for AI coding tools to consume.

Things I would like to add:

- Support for running tests via elm-test-rs.

No published version yet, but you can easily build and try it out locally instructions are in the README.

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**Author:** ![system](https://canada1.discourse-cdn.com/flex035/uploads/elm_lang/original/1X/50a05e53677a2c3b47776d7abd0f113eb50193a1.png) [@system](https://discourse.elm-lang.org/u/system)\
**Post date:** [February 5, 2026, 12:33pm UTC](https://discourse.elm-lang.org/t/improving-elm-coverage/10533/2 "2026-02-05T12:33:26Z")

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