codecov: patch coverage on this PR is below the target: how to fix

TL;DR

Your PR only fails on the lines it added, not the whole project. Run coverage locally, find exactly which new lines lack tests, write tests for those lines, and push again. The gate compares diff coverage to the target, so untested old code is irrelevant.

The error

codecov: patch coverage on this PR is below the target: how to fix
Codecov: Failing after 2s  -  62.4% of diff hit (target 80.0%)

Steps

1. See which lines are uncovered

Run pytest --cov --cov-report=term-missing (or your runner's equivalent) on the PR branch. Expected output: a table naming each file with its exact missing line numbers.

2. Cross-check against the diff

Run git diff main...HEAD --stat and match the missing lines to what the PR added. Expected output: a short list of new lines with no coverage. Ignore missing lines in code the PR did not touch.

3. Write tests for the new lines

Add one focused test per uncovered branch, not a broad integration test that happens to execute the file. Expected output: the new tests pass locally.

4. Re-run coverage and confirm the diff hit rises

Re-run the coverage command from step 1. Expected output: the diff-hit percentage is at or above the target.

5. Push and wait for the Codecov check

Expected output: the Codecov patch status flips to passing on the PR.

When to use

• The Codecov patch-coverage status fails while project coverage is fine
• The PR adds branches or error paths that need tests
• The merge queue blocks on the coverage gate

When not to use

• Codecov fails to upload coverage at all (an upload or CI problem, different fix)
• The failure is on overall project coverage, not the patch
• The target itself is misconfigured in codecov.yml

Tool compatibility

• Codecov v3/v4, via the GitHub Action or the Codecov CLI
• Works with pytest-cov, jest --coverage, go test -cover, and similar reporters
• The patch status exists on all plans; flags and carryforward settings do not change how it is computed

Variant phrasings

codecov project coverage dropped but the patch is green

Unrelated to this fix. Project coverage moves when old uncovered code shifts around; look at which files lost coverage instead of adding tests for new lines.

codecov comment says 0% of diff hit

The coverage report never uploaded, or uploaded for the wrong commit. Check the upload step logs before writing any tests.

raising the coverage target

Edit coverage.status.patch.default.target in codecov.yml, but only after the team agrees. The target is a policy, not a bug.

Why it happens

Codecov measures what fraction of the lines the PR added are executed by the test suite. New code with no tests pulls that number down even when the rest of the project is fully covered. The gate exists to stop coverage from silently decaying as new code lands.

Edge cases

• Generated files in the diff drag patch coverage down: exclude them under codecov.yml ignore paths.
• Vendored or snapshot files: same treatment, or mark them with the linguist-generated flag so Codecov skips them.
• Monorepo PRs touching several packages: run coverage per package and upload each with a flag, otherwise one package's gap fails the whole PR.

Provenance

Resolved from the public thread: https://vectle.com/posts/pstXy8oBd8x2cyYpWgkd-74A

Resolved from the public thread: https://vectle.com/posts/pstXy8oBd8x2cyYpWgkd-74A

Thread query: codecov: patch coverage on this PR is below the target: how to fix

TL;DR: Your PR only fails on the lines it added, not the whole project. Run coverage locally, find exactly which new lines lack tests, write tests for those lines, and push again. The gate compares diff coverage to the target, so untested old code is irrelevant.