Go test coverage profile write failure - Fix in CI

go test -coverprofile writes a single coverage file. When the target directory does not exist, is read-only, or multiple package runs collide on the path, the write fails and the run errors.

What this error means

A coverage run fails with cannot create coverprofile: open cover.out: no such file or directory or permission denied, or the profile ends up empty after a multi-package run. It means the path or write mode is wrong.

go test -coverprofile=reports/cover.out ./...
cannot create 'reports/cover.out': open reports/cover.out: no such file or directory

Common causes

Target directory missing or read-only

The coverprofile path points at a directory that does not exist or cannot be written.

Per-package profiles overwrite each other

Running coverage per package to the same file leaves only the last package, or collides mid-write.

How to fix it

Create the directory and write once

1. Make the output directory and run coverage across all packages into one profile.

mkdir -p reports
go test -coverprofile=reports/cover.out -covermode=atomic ./...

Use a writable path

1. Write the profile to a path the job owns, such as the workspace root.

go test -coverprofile=cover.out ./...

How to prevent it

• Create the output directory before writing the profile.
• Write one combined profile across ./... rather than per package.
• Keep the profile path inside the writable workspace.

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