This morning a one line change had several of us tearing up the fabric of reality trying to understand why a failing test wasn’t failing, or, in fact, being run at all. Increasingly frantic efforts to upgrade/downgrade Go, run the tests on another machine, run the tests in CI, all served to only unnerve us further.

Can you spot the bug?

package gosh_darn_important_test

import (
    "testing"
    "go.uber.org/goleak"
)

func TestMain(m *testing.M) {
//	goleak.VerifyTestMain(m)
}

...

TestMain is intended to be a middleware (so to speak) between the go test test runner and the Test functions in a package. The goleak check had recently been commented out (not surprisingly because of yet another logging library that spawns goroutines in the background) which meant that TestMain no longer called, indirectly, m.Run to execute any tests.