Mix Coverage

Parse mix test.coverage output, post or update a sticky PR comment, and enforce total and per-module coverage thresholds.

Supports both the pre-1.20 table format (plain Percentage | Module) and the markdown-pipe format introduced in Elixir 1.20. Useful for hex packages that test across multiple Elixir versions in the same workflow.

Usage

Minimal — post a sticky PR comment after your test job runs:

- uses: hipcall/mix-coverage-action@v1
  with:
    github-token: ${{ secrets.GITHUB_TOKEN }}

Typical — enforce total and per-module thresholds:

- name: Tests & Coverage
  run: |
    mix test --cover --export-coverage default
    mix test.coverage

- uses: hipcall/mix-coverage-action@v1
  with:
    github-token: ${{ secrets.GITHUB_TOKEN }}
    minimum-coverage: 80
    minimum-module-coverage: 70

Also show a Changed files section in the comment (informational — helps reviewers focus):

- uses: hipcall/mix-coverage-action@v1
  with:
    github-token: ${{ secrets.GITHUB_TOKEN }}
    minimum-coverage: 80
    include-changed-files: true

Parse a pre-captured log instead of running a command:

- uses: hipcall/mix-coverage-action@v1
  with:
    github-token: ${{ secrets.GITHUB_TOKEN }}
    coverage-file: ./cover/summary.txt

Inputs

Name	Required	Default	Description
github-token	yes	—	Token used to post the PR comment. ${{ secrets.GITHUB_TOKEN }} is sufficient.
coverage-command	no	mix test.coverage	Command producing a mix test --cover or mix test.coverage table on stdout. Ignored when coverage-file is set.
coverage-file	no	""	Path to a pre-captured coverage log. When set, coverage-command is skipped.
minimum-coverage	no	0	Fail the step when total coverage is below this percentage. 0 disables.
minimum-module-coverage	no	0	Fail the step when any reported module is below this percentage. Applies to every module. 0 disables.
include-changed-files	no	false	When true on a PR, add a Changed files section to the comment listing modules mapped from files modified in the PR. Informational only — no gate.
comment	no	sticky	PR comment behavior: sticky (create/update marked comment), new, or off.
working-directory	no	.	Directory in which to run coverage-command.

Outputs

Name	Description
total-coverage	Total coverage percentage as a string, e.g. 85.70.
failed-modules	JSON array of modules below the per-module threshold after any changed-files filter.

How it works

1. Runs coverage-command and captures stdout (exit code is ignored — mix test.coverage exits non-zero when its own :threshold is unmet; this action is the single authoritative gate).
2. Parses the 1.20 markdown-pipe table: | Percentage | Module | header, per-module rows, and the trailing Total row.
3. On pull requests, posts or updates a comment marked with an HTML comment so repeat runs update in place.
4. Applies threshold gates and exits non-zero if any fail.

Module-to-file mapping for include-changed-files uses the Elixir naming convention (Macro.underscore of the module name) against the PR's changed file list. Edge cases (multiple modules per file, nested modules split across files) may produce conservative matches.

Elixir configuration tip

Because this action is the authoritative gate, disable mix's built-in threshold by setting it to 0 in your project's mix.exs:

def project do
  [
    # ...
    test_coverage: [summary: [threshold: 0]]
  ]
end

License

MIT © Hipcall