Code Coverage Advance

A GitHub Action that generates code coverage results from a commonly used coverage format. Additionally it generates code coverage for only changed files in PR. Also generates badges, passed/failed outputs.

Description

This action generates a Cobertura code coverage file only on the PR files that have changed. Perfect for teams who want to ensure that new or modified code meets coverage standards without being penalized for legacy code coverage issues. Takes a Cobertura file generated from many test frameworks as input and used but CircleCI, SonarQube, Codecov etc.

Code Coverage Summary

Package	Line Rate	Branch Rate	Health
main	91.0%	61.4%	✅
Summary	91.0% (173 / 190)	61.4% (89 / 145)	✅

Minimum pass threshold is 50.0%

Code Coverage Summary

Package	Line Rate	Branch Rate	Health
main	91.1%	60.8%	✅
Summary	91.1% (173 / 190)	60.8% (59 / 97)	✅

Minimum pass threshold is 50.0%

Some features:

• Generates a modified Cobertura file containing results for only changed files since PR branch creation. Optional.
• Markdown formatted coverage reports
• Coverage badges for both overall and changed files
• Pass/fail checks based on configurable thresholds
• Uncovered lines table grouped by file and method with compressed line ranges (e.g. 21,23,26-31,33)

Usage

IMPORANT: If you find that changes are not detected, checkout the branch with a fetch-depth: 0.

Basic Example

- uses: actions/checkout@v3
    with:
      fetch-depth: 0

# Apply the Cobertura Change Only Action
- name: Check coverage on changed files
  uses: ZeroWiggliness/CodeCoverageAdv@v1
  with:
    cobertura-file: 'coverage/cobertura.xml'
    output-file: 'coverage/changed-only.xml'
    main-branch: 'develop'
    coverage-threshold: '60 80'
    coverage-changes-threshold: '70 90'
    badge-style: 'flat'
    github-token: ${{ secrets.GITHUB_TOKEN }}
    file-filters: 'src/**/*.ts,src/**/*.js,!**/*.test.ts,!**/*.spec.js'
    fail-action: 'true'
    max-missing-lines: '100'

- name: Add coverage comment to PR
        if: github.event_name == 'pull_request'
        uses: marocchino/sticky-pull-request-comment@v2
        with:
          header: coverage
          message: |
            ${{ steps.coverage.outputs.coverage-badge }} ${{ steps.coverage.outputs.coverage-changes-badge }}
            ## Coverage Report

            ${{ steps.coverage.outputs.coverage-markdown }}

            ## Changed Files Coverage

            ${{ steps.coverage.outputs.coverage-changes-markdown }}

            ${{ steps.coverage.outputs.coverage-changes-missing-lines }}

GitLab CI Usage (Docker / cca CLI)

Build the Docker image from the repository root and push it to your registry, then use it as a GitLab CI job image. The cca command accepts the same options as the GitHub Action inputs.

Building the image

docker build -t registry.example.com/cca:latest .
docker push registry.example.com/cca:latest

CLI options

All flags match the GitHub Action input names (hyphenated, prefixed with --).

Flag	Description	Default
--cobertura-file	Path to the Cobertura XML input file	coverage/cobertura-coverage.xml
--output-file	Path to save the filtered coverage XML (MR pipelines only). Empty = disabled.
--main-branch	Branch to compare against for changed-files detection	main
--current-branch	Current branch name (also read from CI_COMMIT_REF_NAME)
--coverage-threshold	<warning%> <success%> for overall coverage	50 75
--coverage-changes-threshold	<warning%> <success%> for changed-file coverage	50 75
--badge-style	Shield.io badge style (flat, flat-square, plastic, for-the-badge, social)	flat
--file-filters	Comma-separated glob patterns to include/exclude	**/*.*
--fail-action	Exit with code 1 when coverage is below threshold	true
--max-missing-lines	Maximum rows in the uncovered lines table	100
--merge-request	Force merge-request mode (changed-files analysis). Auto-detected via CI_PIPELINE_SOURCE / CI_MERGE_REQUEST_IID.	false
--output-json	Path to write all outputs as a JSON file. Prints to stdout if omitted.

Merge-request detection

Changed-file analysis runs automatically when any of these are true:

• CI_PIPELINE_SOURCE=merge_request_event (set by GitLab on MR pipelines)
• CI_MERGE_REQUEST_IID is set
• --current-branch differs from --main-branch
• --merge-request flag is passed explicitly

Changed files are resolved with git merge-base origin/<main-branch> HEAD + git diff --name-only. A full clone (GIT_DEPTH: 0) is required.

Basic GitLab CI example

coverage:
  image: registry.example.com/cca:latest
  variables:
    GIT_DEPTH: 0
  script:
    - <your test command that generates a Cobertura XML>
    - cca --cobertura-file coverage/cobertura-coverage.xml --main-branch main --coverage-threshold "60 80" --coverage-changes-threshold "70 90" --file-filters "src/**/*.ts,!**/*.test.ts" --output-json cca-output.json
  artifacts:
    paths:
      - cca-output.json

Running locally for testing

Mount your project directory into the container so the tool can read the Cobertura file and access the git history.

Overall coverage only (no branch comparison):

docker run --rm \
  -v "$(pwd):/workspace" \
  -w /workspace \
  registry.example.com/cca:latest \
  cca --cobertura-file coverage/cobertura-coverage.xml \
      --coverage-threshold "60 80" \
      --output-json /workspace/cca-output.json

cat cca-output.json

Simulating a merge-request pipeline (changed-files analysis):

The git history must be available inside the container. Mount the repo root (which contains .git) and make sure origin/<main-branch> is fetchable — the branch must already be fetched locally.

# Ensure the main branch ref is available locally
git fetch origin main

docker run --rm \
  -v "$(pwd):/workspace" \
  -w /workspace \
  registry.example.com/cca:latest \
  cca --cobertura-file coverage/cobertura-coverage.xml \
      --main-branch main \
      --current-branch feature/my-branch \
      --coverage-threshold "60 80" \
      --coverage-changes-threshold "70 90" \
      --file-filters "src/**/*.ts,!**/*.test.ts" \
      --output-json /workspace/cca-output.json

cat cca-output.json

Windows (PowerShell): replace $(pwd) with ${PWD}.

Piping the output directly to jq:

docker run --rm \
  -v "$(pwd):/workspace" \
  -w /workspace \
  registry.example.com/cca:latest \
  cca --cobertura-file coverage/cobertura-coverage.xml | jq '.["coverage-passrate"]'

Consuming the JSON output in a later job

All GitHub Action outputs are written as keys in the JSON file:

{
  "coverage-badge": "![Code Coverage](...)",
  "coverage-markdown": "## Code Coverage Summary\n...",
  "coverage-passrate": "74.4%",
  "coverage-failed": "false",
  "coverage-missing-lines": "## Uncovered Lines\n...",
  "coverage-changes-badge": "![Code Changes Coverage](...)",
  "coverage-changes-markdown": "## Code Coverage Summary\n...",
  "coverage-changes-passrate": "88.0%",
  "coverage-changes-failed": "false",
  "coverage-changes-missing-lines": "## Uncovered Lines\n..."
}

Use jq or any JSON tool to extract individual values in downstream jobs:

post-coverage:
  needs: [coverage]
  script:
    - BADGE=$(jq -r '.["coverage-badge"]' cca-output.json)
    - echo "Coverage badge $BADGE"

Inputs

Input	Description	Required	Default
cobertura-file	Path to the Cobertura XML input file	Yes	coverage/cobertura-coverage.xml
output-file	Path to save the filtered coverage output file. Empty = No OutputFile.	No
main-branch	Name of the main branch to compare against.	No	${{ github.repository_default_branch }}
coverage-threshold	Thresholds for coverage percentage health <warning% <success%>	No	50 75
coverage-changes-threshold	Thresholds for changed files coverage.	No	50 75
badge-style	GitHub badge style to use.	No	flat
github-token	GitHub token for accessing the repository.	No	${{ github.token }}
current-branch	Name of the current branch.	No	${{ github.head_ref || github.ref_name }}
file-filters	Comma-separated list of file patterns.	No	**/*.*
fail-action	Whether to fail if coverage is below threshold.	No	true
max-missing-lines	Maximum rows to show in the uncovered lines table.	No	100

Outputs

Output	Description
coverage-markdown	Markdown formatted overall coverage report
coverage-changes-markdown	Markdown formatted report for changed files only
coverage-passrate	Overall coverage pass rate
coverage-changes-passrate	Changed files coverage pass rate
coverage-badge	Overall coverage badge markdown
coverage-changes-badge	Changed files coverage badge markdown
coverage-failed	true if overall coverage is below threshold
coverage-changes-failed	true if changed files coverage is below threshold
coverage-missing-lines	Markdown table of uncovered lines grouped by file and method (overall)
coverage-changes-missing-lines	Markdown table of uncovered lines grouped by file and method (changes only)

Differences

The quality of the calculations depends on the Cobertura file supplied to the action. For some reason I cant get it with exactly the same branch results but it generates the right results.

dotCover/reportGenerator doesnt generate branch results. jest cobertura (as used for this) generates branch counts I cant replicate.

Building and Bundling

To build and bundle this action:

1. Clone the repository

   git clone https://github.com/your-username/cobertura-change-only.git
   cd cobertura-change-only

2. Install dependencies

   npm install

3. Format and lint the code

   npm run format:write

4. Bundle the action for distribution

   npm run bundle

This will create a dist/index.js file that contains the bundled action code, which is referenced in the action.yml file.

License

MIT