Remove dependency on cmp package

testcerts.go

@@ -62,7 +62,6 @@ Simplify your testing, and don't hassle with certificates anymore.
 package testcerts
 
 import (
-	"cmp"
 	"crypto/ecdsa"
 	"crypto/elliptic"
 	"crypto/rand"
@@ -159,6 +158,12 @@ func (ca *CertificateAuthority) NewKeyPairFromConfig(config KeyPairConfig) (*Key
 		return nil, err
 	}
 
+	// If a serial number is provided, use it, otherwise use 42
+	serialNumber := config.SerialNumber
+	if serialNumber == nil {
+		serialNumber = big.NewInt(42)
+	}
+
 	// Create a Certificate
 	kp := &KeyPair{cert: &x509.Certificate{
 		Subject: pkix.Name{
@@ -167,7 +172,7 @@ func (ca *CertificateAuthority) NewKeyPairFromConfig(config KeyPairConfig) (*Key
 		},
 		DNSNames:     config.Domains,
 		IPAddresses:  ips,
-		SerialNumber: cmp.Or(config.SerialNumber, big.NewInt(42)),
+		SerialNumber: serialNumber,
 		NotBefore:    time.Now().Add(-1 * time.Hour),
 		NotAfter:     time.Now().Add(2 * time.Hour),
 		ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageClientAuth, x509.ExtKeyUsageServerAuth},