coverage

GitHub Action that parses coverage files and posts sticky PR comments with per-file deltas.

Features • Usage • Inputs • Outputs • Coverage Files • Development

Why

Most coverage reporting actions require third-party services or complex setups. This action works entirely within GitHub Actions using built-in cache, supports multiple languages, and shows meaningful per-file diffs without external dependencies.

Features

• Supports any LCOV-producing tool (Bun, Jest, c8, nyc, Istanbul, PHPUnit, …) and Go coverage
• Shows per-file coverage deltas against base branch
• Single sticky PR comment (updates existing, no spam)
• Uses @actions/cache for cross-run comparison
• Optional thresholds and fail-on-decrease
• No external services or tokens required

Output example

Usage

- uses: xseman/coverage@v0.2.0
  with:
      coverage-artifact-paths: bun:coverage/lcov.info

With multiple tools and thresholds:

- uses: xseman/coverage@v0.2.0
  with:
      coverage-artifact-paths: |
          bun:coverage/lcov.info
          go:coverage.out
      fail-on-decrease: true
      coverage-threshold: 80

Full workflow:

name: Coverage
on: pull_request

jobs:
    test:
        runs-on: ubuntu-latest
        steps:
            - uses: actions/checkout@v6
            - uses: oven-sh/setup-bun@v2
            - run: bun install
            - run: bun test --coverage --coverage-reporter=lcov

            - uses: xseman/coverage@v0.2.0
              with:
                  coverage-artifact-paths: bun:coverage/lcov.info

How it works

---
config:
  theme: neutral
  themeVariables:
    fontFamily: monospace
    fontSize: "10px"
---
sequenceDiagram
    participant F as Filesystem
    participant A as Action
    participant C as Cache
    participant G as GitHub

    F->>A: read coverage file
    A->>C: restore base coverage
    A->>A: compute deltas
    A->>G: post PR comment
    A->>C: save new coverage

Loading

Each <tool>:<path> entry goes through this pipeline independently. Results are combined into one PR comment. The action caches parsed coverage as JSON via @actions/cache using key {prefix}-{tool}-{branch}-{sha}, restoring by prefix match to find the latest base-branch snapshot.

Inputs

Input	Default	Description
coverage-artifact-paths	(required)	Newline or comma-separated <tool>:<path> entries
base-branch	PR base ref	Branch for delta comparison
cache-key	coverage-reporter	Cache key prefix
update-comment-marker	<!-- coverage-reporter-sticky -->	HTML marker for sticky comment
colorize	on	[+]/[-] delta markers (on/off)
fail-on-decrease	false	Fail if coverage decreases
coverage-threshold	0	Minimum overall coverage % (0 = disabled)
github-token	${{ github.token }}	Token for PR comments

Supported tools

Tool	Format	Example
bun	LCOV	bun:coverage/lcov.info
lcov	LCOV (generic)	lcov:coverage/lcov.info
go	Go cover profile	go:coverage.out
gocover	Go cover profile	gocover:coverage.out

Outputs

Output	Description
overall-coverage	Overall coverage percentage (e.g., 82.50)
coverage-decreased	true if any file coverage decreased
comment-id	ID of created/updated PR comment

Generating coverage files

# Bun (produces LCOV)
bun test --coverage --coverage-reporter=lcov

# Go
go test -coverprofile=coverage.out ./...

Development

bun install    # install dependencies
bun test       # run tests
bun run lint   # typecheck + format check
bun run build  # bundle to lib/index.mjs

Related

• actions/cache
• Bun test coverage
• Go test coverage