How to Enable Branch Coverage vs Line Coverage in CI

By Daniel Zoghalchali·Latchkey

Line coverage counts executed lines; branch coverage checks that each conditional path is exercised.

Enable branch mode explicitly: coverage.py branch = true, Go -covermode=atomic, and Jest already tracks branches via the branches threshold. Branch coverage catches an untested else a line metric would miss.

coverage.py (branch on)

.coveragerc

[run]
branch = true
source = ["myapp"]

Jest (branch threshold)

jest.config.js

module.exports = {
  coverageThreshold: {
    global: { lines: 80, branches: 80 },
  },
};

Gotchas

Branch coverage is always lower than line coverage on the same code; set thresholds accordingly.
A line can be fully covered while one of its branches is never taken, which is exactly what branch mode surfaces.

Verify it actually works

A workflow that runs is not a workflow that works. Confirm the behaviour on a real event rather than on a manual dispatch, because trigger conditions, permissions, and context values all differ between the two.

Terminal

# 1. validate the file before pushing
docker run --rm -v "$(pwd):/repo" --workdir /repo rhysd/actionlint:latest -color

# 2. trigger the real event, not workflow_dispatch
git commit --allow-empty -m "ci: verify trigger" && git push

# 3. watch it and read the conclusion, not just the colour
gh run watch
gh run view --log-failed

What usually goes wrong first

The workflow file must exist on the default branch before scheduled or dispatch triggers appear at all.
GITHUB_TOKEN permissions default to read-only in many organisations. Declare a permissions: block listing every scope the job needs.
Fork pull requests get a read-only token and no access to secrets, regardless of workflow configuration.
actions/checkout gives you depth 1 on a detached HEAD, so anything needing history or a branch name needs fetch-depth: 0.

Frequently asked questions

How do I enable Branch Coverage vs Line Coverage in CI?

Enable branch mode explicitly: coverage.py branch = true, Go -covermode=atomic, and Jest already tracks branches via the branches threshold. Branch coverage catches an untested else a line metric would miss.

References

GitHub Actions documentation