t.Errorf("#%d: %q parsed as (%q, %q), but wanted (%q, %q)", i, test.in, mailbox.local, mailbox.domain, test.localPart, test.domain)
		}
	}
}

func TestBadNamesInConstraints(t *testing.T) {
	constraintParseError := func(err error) bool {
		str := err.Error()
		return strings.Contains(str, "failed to parse ") && strings.Contains(str, "constraint")
	}