if !strings.HasPrefix(strOut, expected) {
		t.Errorf("expected prefix: %q", expected)
	}
}

// Test for https://go.dev/issue/19661: unshare fails because systemd
// has forced / to be shared
func TestUnshareMountNameSpace(t *testing.T) {
	const mountNotSupported = "mount is not supported: " // Output prefix indicating a test skip.
	if os.Getenv("GO_WANT_HELPER_PROCESS") == "1" {
		dir := flag.Args()[0]