if err != nil {
				t.Errorf("%d - failed to create cert %d: %v", i, j, err)
				continue NextTest
			}

			sniCerts = append(sniCerts, certProvider)

			sig, err := certSignature(certProvider)
			if err != nil {
				t.Errorf("%d - failed to get signature for %d: %v", i, j, err)
				continue NextTest
			}
			bySignature[sig] = j
		}

}

func certFileSignature(certFile, keyFile string) (string, error) {
	cert, err := tls.LoadX509KeyPair(certFile, keyFile)
	if err != nil {
		return "", err
	}
	return certSignature(cert)
}

func certSignature(cert tls.Certificate) (string, error) {
	x509Certs, err := x509.ParseCertificates(cert.Certificate[0])
	if err != nil {
		return "", err
	}
	return x509CertSignature(x509Certs[0]), nil
}