Go test failures — FAIL / panic: test timed out

Log signatures

--- FAIL: TestName
FAIL	github.com/you/pkg	0.42s
undefined: SomeIdentifier
panic: test timed out after 10m0s

What’s happening

Go's signatures are terse and precise. FAIL\t (FAIL + tab) is the per-package failure line — FAIL github.com/you/pkg 0.42s. "undefined:" is a compile error inside test scope: tests failed to build, often because a test file references an identifier renamed in the main code, or a build tag excluded the file that defines it — nothing actually ran. "panic: test timed out" is Go's 10-minute default test binary timeout: either a genuine deadlock (the panic includes a full goroutine dump — read it, the stuck goroutine is in there) or a suite that legitimately outgrew the limit.

Fix playbook

1. 1Rerun only the failing package and test: go test ./pkg/... -run 'TestName' -v.
2. 2undefined:: treat as a compile fix. Check build tags (//go:build) if the identifier clearly exists — the file defining it may be excluded for this OS/arch.
3. 3panic: test timed out: read the goroutine dump at the bottom of the log. Goroutines blocked on a channel/mutex for the full duration name the deadlock. If it's genuinely slow, raise -timeout consciously.
4. 4Race-flavored flakiness: rerun with -race -count=10. A test that fails intermittently under -count=10 has a real concurrency bug, not "CI weirdness."
5. 5Fix the narrowest site and rerun the package before ./....