test: comprehensive test gap closure across 24 packages

Close coverage gaps identified by dual-audit (qualitative + quantitative).
New test files for config (0%→98%), router (0%→100%), handler validation,
health, audit, response helpers, webhook notifier (0%→88%), email notifier,
middleware (recovery, rate limiter), domain profile, service nil-safety,
config helpers, issuer bootstrap, and server bootstrap wiring. Expanded
existing tests for ACME (34%→42%), step-ca (42%→52%), F5, SSH, agent
(43%→63%), scheduler (88%→99%), renewal service, and issuerfactory.

All tests pass: go test -short, go vet, go test -race clean.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/connector/issuer/acme/acme_test.go

@@ -2,15 +2,25 @@ package acme
 
 import (
 	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/x509"
+	"crypto/x509/pkix"
 	"encoding/base64"
 	"encoding/json"
+	"encoding/pem"
 	"fmt"
 	"log/slog"
+	"math/big"
 	"net/http"
 	"net/http/httptest"
 	"os"
 	"strings"
 	"testing"
+	"time"
+
+	"github.com/shankar0123/certctl/internal/connector/issuer"
 )
 
 func testLogger() *slog.Logger {
@@ -262,3 +272,775 @@ func TestEnsureClient_ZeroSSLAutoEAB(t *testing.T) {
 		t.Errorf("expected auto-fetched EABHmac, got: %s", c.config.EABHmac)
 	}
 }
+
+// --- parseCSRPEM tests ---
+
+func TestParseCSRPEM_ValidPEM(t *testing.T) {
+	// Generate a real ECDSA P-256 CSR using crypto/x509
+	key, err := generateTestKey()
+	if err != nil {
+		t.Fatalf("failed to generate test key: %v", err)
+	}
+
+	csrTemplate := x509.CertificateRequest{
+		Subject:   generateTestName("test.example.com"),
+		DNSNames:  []string{"test.example.com", "www.test.example.com"},
+		PublicKey: &key.PublicKey,
+	}
+
+	csrDER, err := x509.CreateCertificateRequest(nil, &csrTemplate, key)
+	if err != nil {
+		t.Fatalf("failed to create CSR: %v", err)
+	}
+
+	csrPEM := string(pem.EncodeToMemory(&pem.Block{
+		Type:  "CERTIFICATE REQUEST",
+		Bytes: csrDER,
+	}))
+
+	// Test parseCSRPEM
+	result, err := parseCSRPEM(csrPEM)
+	if err != nil {
+		t.Fatalf("parseCSRPEM failed: %v", err)
+	}
+
+	if len(result) == 0 {
+		t.Fatal("expected non-empty DER bytes")
+	}
+
+	// Verify it's valid DER by parsing it
+	parsed, err := x509.ParseCertificateRequest(result)
+	if err != nil {
+		t.Fatalf("failed to parse result as valid CSR: %v", err)
+	}
+
+	if !strings.Contains(parsed.Subject.String(), "test.example.com") {
+		t.Errorf("expected CN in parsed CSR, got: %s", parsed.Subject.String())
+	}
+}
+
+func TestParseCSRPEM_InvalidPEM(t *testing.T) {
+	tests := []struct {
+		name    string
+		pem     string
+		wantErr bool
+	}{
+		{"empty string", "", true},
+		{"not PEM format", "not-a-pem", true},
+		{"valid PEM but wrong type", "-----BEGIN CERTIFICATE-----\ntest\n-----END CERTIFICATE-----", true},
+		{"invalid base64", "-----BEGIN CERTIFICATE REQUEST-----\n!!!not-valid-base64!!!\n-----END CERTIFICATE REQUEST-----", true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := parseCSRPEM(tt.pem)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("parseCSRPEM() error = %v, wantErr = %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+// --- parseDERChain tests ---
+
+func TestParseDERChain_ValidChain(t *testing.T) {
+	// Generate a root and leaf certificate for testing
+	rootKey, err := generateTestKey()
+	if err != nil {
+		t.Fatalf("failed to generate root key: %v", err)
+	}
+
+	leafKey, err := generateTestKey()
+	if err != nil {
+		t.Fatalf("failed to generate leaf key: %v", err)
+	}
+
+	// Root cert (self-signed)
+	rootTemplate := x509.Certificate{
+		Subject:               generateTestName("Root CA"),
+		SerialNumber:          big.NewInt(1),
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().AddDate(10, 0, 0),
+		KeyUsage:              x509.KeyUsageCertSign,
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+	}
+
+	rootDER, err := x509.CreateCertificate(nil, &rootTemplate, &rootTemplate, &rootKey.PublicKey, rootKey)
+	if err != nil {
+		t.Fatalf("failed to create root cert: %v", err)
+	}
+
+	// Leaf cert (signed by root)
+	leafTemplate := x509.Certificate{
+		Subject:      generateTestName("test.example.com"),
+		SerialNumber: big.NewInt(100),
+		DNSNames:     []string{"test.example.com", "www.test.example.com"},
+		NotBefore:    time.Now(),
+		NotAfter:     time.Now().AddDate(1, 0, 0),
+		KeyUsage:     x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
+		PublicKey:    &leafKey.PublicKey,
+	}
+
+	leafDER, err := x509.CreateCertificate(nil, &leafTemplate, &rootTemplate, &leafKey.PublicKey, rootKey)
+	if err != nil {
+		t.Fatalf("failed to create leaf cert: %v", err)
+	}
+
+	// Parse the chain
+	certPEM, chainPEM, serial, notBefore, notAfter, err := parseDERChain([][]byte{leafDER, rootDER})
+	if err != nil {
+		t.Fatalf("parseDERChain failed: %v", err)
+	}
+
+	// Verify leaf cert PEM
+	if !strings.Contains(certPEM, "BEGIN CERTIFICATE") {
+		t.Errorf("certPEM should contain PEM header, got: %s", certPEM)
+	}
+
+	// Verify chain PEM contains root
+	if !strings.Contains(chainPEM, "BEGIN CERTIFICATE") {
+		t.Errorf("chainPEM should contain root cert PEM, got: %s", chainPEM)
+	}
+
+	// Verify serial is correctly extracted
+	if serial != "100" {
+		t.Errorf("expected serial '100', got: %s", serial)
+	}
+
+	// Verify timestamps are set
+	if notBefore.IsZero() {
+		t.Error("notBefore should not be zero")
+	}
+	if notAfter.IsZero() {
+		t.Error("notAfter should not be zero")
+	}
+
+	// Verify we can parse the returned PEM
+	block, _ := pem.Decode([]byte(certPEM))
+	if block == nil {
+		t.Fatal("failed to decode returned certPEM")
+	}
+
+	parsedLeaf, err := x509.ParseCertificate(block.Bytes)
+	if err != nil {
+		t.Fatalf("failed to parse returned certPEM: %v", err)
+	}
+
+	if parsedLeaf.SerialNumber.Cmp(big.NewInt(100)) != 0 {
+		t.Errorf("parsed leaf serial mismatch: got %v, expected 100", parsedLeaf.SerialNumber)
+	}
+}
+
+func TestParseDERChain_SingleCert(t *testing.T) {
+	// Generate a single certificate
+	key, err := generateTestKey()
+	if err != nil {
+		t.Fatalf("failed to generate key: %v", err)
+	}
+
+	template := x509.Certificate{
+		Subject:      generateTestName("test.example.com"),
+		SerialNumber: big.NewInt(42),
+		NotBefore:    time.Now(),
+		NotAfter:     time.Now().AddDate(1, 0, 0),
+		KeyUsage:     x509.KeyUsageDigitalSignature,
+		PublicKey:    &key.PublicKey,
+	}
+
+	certDER, err := x509.CreateCertificate(nil, &template, &template, &key.PublicKey, key)
+	if err != nil {
+		t.Fatalf("failed to create cert: %v", err)
+	}
+
+	certPEM, chainPEM, serial, notBefore, notAfter, err := parseDERChain([][]byte{certDER})
+	if err != nil {
+		t.Fatalf("parseDERChain failed: %v", err)
+	}
+
+	if !strings.Contains(certPEM, "BEGIN CERTIFICATE") {
+		t.Error("certPEM should contain PEM header")
+	}
+
+	if chainPEM != "" {
+		t.Errorf("chainPEM should be empty for single cert, got: %s", chainPEM)
+	}
+
+	if serial != "42" {
+		t.Errorf("expected serial '42', got: %s", serial)
+	}
+
+	if notBefore.IsZero() || notAfter.IsZero() {
+		t.Error("timestamps should be set")
+	}
+}
+
+func TestParseDERChain_EmptyChain(t *testing.T) {
+	_, _, _, _, _, err := parseDERChain([][]byte{})
+	if err == nil {
+		t.Fatal("expected error for empty chain")
+	}
+	if !strings.Contains(err.Error(), "empty") {
+		t.Errorf("expected 'empty' in error message, got: %v", err)
+	}
+}
+
+func TestParseDERChain_InvalidDER(t *testing.T) {
+	// Invalid DER bytes
+	invalidDER := []byte{0xFF, 0xFF, 0xFF}
+	_, _, _, _, _, err := parseDERChain([][]byte{invalidDER})
+	if err == nil {
+		t.Fatal("expected error for invalid DER")
+	}
+}
+
+// --- IssueCertificate / RenewCertificate error path tests ---
+// Note: Full IssueCertificate/RenewCertificate testing requires an ACME server.
+// We test the CSR parsing logic which is the first step.
+
+func TestIssueCertificateCSRParsing(t *testing.T) {
+	tests := []struct {
+		name    string
+		csrPEM  string
+		wantErr bool
+	}{
+		{"invalid PEM", "not-a-valid-csr-pem", true},
+		{"empty PEM", "", true},
+		{"wrong PEM type", "-----BEGIN CERTIFICATE-----\nMIID\n-----END CERTIFICATE-----", true},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			_, err := parseCSRPEM(tt.csrPEM)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("parseCSRPEM() error = %v, wantErr = %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+// --- RevokeCertificate behavior test ---
+// ACME revocation is not fully supported in V1 — it requires certificate DER, not just the serial.
+// Full testing would require an ACME server; we verify the basic interface behavior.
+// Skipped here because it requires network access for ACME client initialization.
+
+// --- GenerateCRL and SignOCSPResponse error path tests ---
+
+func TestGenerateCRL_NotSupported(t *testing.T) {
+	c := New(&Config{
+		DirectoryURL: "https://example.com/acme/directory",
+		Email:        "test@example.com",
+	}, testLogger())
+
+	_, err := c.GenerateCRL(context.Background(), nil)
+	if err == nil {
+		t.Fatal("expected error for CRL generation")
+	}
+	if !strings.Contains(err.Error(), "not support") {
+		t.Errorf("expected 'not support' in error, got: %v", err)
+	}
+}
+
+func TestSignOCSPResponse_NotSupported(t *testing.T) {
+	c := New(&Config{
+		DirectoryURL: "https://example.com/acme/directory",
+		Email:        "test@example.com",
+	}, testLogger())
+
+	req := issuer.OCSPSignRequest{
+		CertSerial: big.NewInt(123),
+	}
+
+	_, err := c.SignOCSPResponse(context.Background(), req)
+	if err == nil {
+		t.Fatal("expected error for OCSP signing")
+	}
+	if !strings.Contains(err.Error(), "not support") {
+		t.Errorf("expected 'not support' in error, got: %v", err)
+	}
+}
+
+func TestGetCACertPEM_NotSupported(t *testing.T) {
+	c := New(&Config{
+		DirectoryURL: "https://example.com/acme/directory",
+		Email:        "test@example.com",
+	}, testLogger())
+
+	_, err := c.GetCACertPEM(context.Background())
+	if err == nil {
+		t.Fatal("expected error for GetCACertPEM")
+	}
+	if !strings.Contains(err.Error(), "not") {
+		t.Errorf("expected error message, got: %v", err)
+	}
+}
+
+// --- httpClient behavior tests ---
+
+func TestHttpClient_DefaultTimeout(t *testing.T) {
+	c := New(&Config{
+		DirectoryURL: "https://example.com/acme/directory",
+		Email:        "test@example.com",
+		Insecure:     false,
+	}, testLogger())
+
+	client := c.httpClient()
+	if client == nil {
+		t.Fatal("httpClient should not be nil")
+	}
+	if client.Timeout == 0 {
+		t.Error("httpClient should have a non-zero timeout")
+	}
+}
+
+func TestHttpClient_InsecureSkipVerify(t *testing.T) {
+	c := New(&Config{
+		DirectoryURL: "https://example.com/acme/directory",
+		Email:        "test@example.com",
+		Insecure:     true,
+	}, testLogger())
+
+	client := c.httpClient()
+	if client == nil {
+		t.Fatal("httpClient should not be nil")
+	}
+
+	// Verify that the transport has InsecureSkipVerify enabled
+	if client.Transport == nil {
+		t.Error("client transport should be set for insecure mode")
+	} else {
+		transport := client.Transport.(*http.Transport)
+		if transport.TLSClientConfig == nil || !transport.TLSClientConfig.InsecureSkipVerify {
+			t.Error("TLS config should have InsecureSkipVerify=true")
+		}
+	}
+}
+
+// --- buildIdentifiers tests ---
+
+func TestBuildIdentifiers_CommonNameOnly(t *testing.T) {
+	identifiers := buildIdentifiers("example.com", nil)
+	if len(identifiers) != 1 {
+		t.Fatalf("expected 1 identifier, got %d", len(identifiers))
+	}
+	if identifiers[0].Value != "example.com" {
+		t.Errorf("expected 'example.com', got %s", identifiers[0].Value)
+	}
+}
+
+func TestBuildIdentifiers_CommonNameAndSANs(t *testing.T) {
+	identifiers := buildIdentifiers("example.com", []string{"www.example.com", "api.example.com"})
+	if len(identifiers) != 3 {
+		t.Fatalf("expected 3 identifiers, got %d", len(identifiers))
+	}
+
+	expected := map[string]bool{
+		"example.com":     true,
+		"www.example.com": true,
+		"api.example.com": true,
+	}
+
+	for _, id := range identifiers {
+		if !expected[id.Value] {
+			t.Errorf("unexpected identifier: %s", id.Value)
+		}
+		if id.Type != "dns" {
+			t.Errorf("expected type 'dns', got %s", id.Type)
+		}
+	}
+}
+
+func TestBuildIdentifiers_DeduplicatesCommonName(t *testing.T) {
+	// If CommonName is also in SANs, it should only appear once
+	identifiers := buildIdentifiers("example.com", []string{"example.com", "www.example.com"})
+	if len(identifiers) != 2 {
+		t.Fatalf("expected 2 identifiers (deduplicated), got %d", len(identifiers))
+	}
+}
+
+func TestBuildIdentifiers_EmptyCommonName(t *testing.T) {
+	identifiers := buildIdentifiers("", []string{"www.example.com"})
+	if len(identifiers) != 1 {
+		t.Fatalf("expected 1 identifier, got %d", len(identifiers))
+	}
+	if identifiers[0].Value != "www.example.com" {
+		t.Errorf("expected 'www.example.com', got %s", identifiers[0].Value)
+	}
+}
+
+// --- New constructor tests ---
+
+func TestNew_WithNilConfig(t *testing.T) {
+	c := New(nil, testLogger())
+	if c == nil {
+		t.Fatal("New should return a non-nil Connector")
+	}
+	if c.config != nil {
+		t.Error("config should be nil when initialized with nil")
+	}
+	if len(c.challengeTokens) != 0 {
+		t.Error("challengeTokens should be initialized as empty map")
+	}
+}
+
+func TestNew_WithHTTPPort0DefaultsTo80(t *testing.T) {
+	cfg := &Config{
+		DirectoryURL:  "https://example.com/acme",
+		Email:         "test@example.com",
+		HTTPPort:      0, // Should default to 80
+		ChallengeType: "http-01",
+	}
+	c := New(cfg, testLogger())
+	if c.config.HTTPPort != 80 {
+		t.Errorf("expected HTTPPort to default to 80, got %d", c.config.HTTPPort)
+	}
+}
+
+func TestNew_WithChallengeTypeDefaultsToHTTP01(t *testing.T) {
+	cfg := &Config{
+		DirectoryURL: "https://example.com/acme",
+		Email:        "test@example.com",
+		HTTPPort:     8080,
+		// ChallengeType intentionally empty
+	}
+	c := New(cfg, testLogger())
+	if c.config.ChallengeType != "http-01" {
+		t.Errorf("expected ChallengeType to default to http-01, got %s", c.config.ChallengeType)
+	}
+}
+
+func TestNew_WithDNSPropagationWaitDefaultsTo30(t *testing.T) {
+	cfg := &Config{
+		DirectoryURL:  "https://example.com/acme",
+		Email:         "test@example.com",
+		ChallengeType: "dns-01",
+		// DNSPropagationWait intentionally 0
+	}
+	c := New(cfg, testLogger())
+	if c.config.DNSPropagationWait != 30 {
+		t.Errorf("expected DNSPropagationWait to default to 30, got %d", c.config.DNSPropagationWait)
+	}
+}
+
+func TestNew_InitializesDNSSolverForDNS01(t *testing.T) {
+	cfg := &Config{
+		DirectoryURL:     "https://example.com/acme",
+		Email:            "test@example.com",
+		ChallengeType:    "dns-01",
+		DNSPresentScript: "/bin/sh", // Use a real script that exists
+	}
+	c := New(cfg, testLogger())
+	// DNS solver should be initialized for dns-01
+	if c.dnsSolver == nil && cfg.DNSPresentScript != "" {
+		// Note: it only initializes if the script path is not empty
+		t.Error("dnsSolver should be initialized for dns-01 with present script")
+	}
+}
+
+func TestNew_InitializesDNSSolverForDNSPersist01(t *testing.T) {
+	cfg := &Config{
+		DirectoryURL:     "https://example.com/acme",
+		Email:            "test@example.com",
+		ChallengeType:    "dns-persist-01",
+		DNSPresentScript: "/bin/sh", // Use a real script path
+	}
+	c := New(cfg, testLogger())
+	if c.dnsSolver == nil && cfg.DNSPresentScript != "" {
+		t.Error("dnsSolver should be initialized for dns-persist-01 with present script")
+	}
+}
+
+func TestNew_NooDNSSolverForHTTP01(t *testing.T) {
+	cfg := &Config{
+		DirectoryURL:     "https://example.com/acme",
+		Email:            "test@example.com",
+		ChallengeType:    "http-01",
+		DNSPresentScript: "/nonexistent/path", // Intentionally not initialized
+	}
+	c := New(cfg, testLogger())
+	if c.dnsSolver != nil {
+		t.Error("dnsSolver should not be initialized for http-01")
+	}
+}
+
+// --- ValidateConfig additional coverage tests ---
+
+func TestValidateConfig_DNSPresentScriptRequired(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprint(w, `{"newNonce":"","newAccount":"","newOrder":""}`)
+	}))
+	defer srv.Close()
+
+	c := New(nil, testLogger())
+	cfg, _ := json.Marshal(map[string]string{
+		"directory_url":  srv.URL,
+		"email":          "test@example.com",
+		"challenge_type": "dns-01",
+		// Missing dns_present_script
+	})
+
+	err := c.ValidateConfig(context.Background(), cfg)
+	if err == nil {
+		t.Fatal("expected error when dns_present_script is missing for dns-01")
+	}
+	if !strings.Contains(err.Error(), "dns_present_script") {
+		t.Errorf("expected 'dns_present_script' in error, got: %v", err)
+	}
+}
+
+func TestValidateConfig_DNSPersistIssuerDomainRequired(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprint(w, `{"newNonce":"","newAccount":"","newOrder":""}`)
+	}))
+	defer srv.Close()
+
+	c := New(nil, testLogger())
+	cfg, _ := json.Marshal(map[string]string{
+		"directory_url":     srv.URL,
+		"email":             "test@example.com",
+		"challenge_type":    "dns-persist-01",
+		"dns_present_script": "/tmp/script.sh",
+		// Missing dns_persist_issuer_domain
+	})
+
+	err := c.ValidateConfig(context.Background(), cfg)
+	if err == nil {
+		t.Fatal("expected error when dns_persist_issuer_domain is missing for dns-persist-01")
+	}
+	if !strings.Contains(err.Error(), "dns_persist_issuer_domain") {
+		t.Errorf("expected 'dns_persist_issuer_domain' in error, got: %v", err)
+	}
+}
+
+func TestValidateConfig_InvalidJSON(t *testing.T) {
+	c := New(nil, testLogger())
+	err := c.ValidateConfig(context.Background(), []byte("{invalid json}"))
+	if err == nil {
+		t.Fatal("expected error for invalid JSON")
+	}
+	if !strings.Contains(err.Error(), "invalid") {
+		t.Errorf("expected 'invalid' in error, got: %v", err)
+	}
+}
+
+// Note: Profile validation tests are in profile_test.go
+
+func TestValidateConfig_ACMEDirectoryUnreachable(t *testing.T) {
+	c := New(nil, testLogger())
+	cfg, _ := json.Marshal(map[string]string{
+		"directory_url": "https://127.0.0.1:1/directory", // Unreachable
+		"email":         "test@example.com",
+	})
+
+	err := c.ValidateConfig(context.Background(), cfg)
+	if err == nil {
+		t.Fatal("expected error for unreachable ACME directory")
+	}
+}
+
+func TestValidateConfig_HTTPStatusError(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusNotFound)
+	}))
+	defer srv.Close()
+
+	c := New(nil, testLogger())
+	cfg, _ := json.Marshal(map[string]string{
+		"directory_url": srv.URL,
+		"email":         "test@example.com",
+	})
+
+	err := c.ValidateConfig(context.Background(), cfg)
+	if err == nil {
+		t.Fatal("expected error for non-2xx status")
+	}
+	if !strings.Contains(err.Error(), "404") {
+		t.Errorf("expected '404' in error, got: %v", err)
+	}
+}
+
+func TestValidateConfig_DNS01WithPresentScript(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprint(w, `{"newNonce":"","newAccount":"","newOrder":""}`)
+	}))
+	defer srv.Close()
+
+	c := New(nil, testLogger())
+	cfg, _ := json.Marshal(map[string]string{
+		"directory_url":     srv.URL,
+		"email":             "test@example.com",
+		"challenge_type":    "dns-01",
+		"dns_present_script": "/bin/sh",
+		"dns_cleanup_script": "/bin/sh",
+	})
+
+	err := c.ValidateConfig(context.Background(), cfg)
+	if err != nil {
+		t.Fatalf("expected DNS-01 with present script to succeed, got: %v", err)
+	}
+
+	// Verify config was updated
+	if c.config.ChallengeType != "dns-01" {
+		t.Errorf("expected ChallengeType=dns-01, got %s", c.config.ChallengeType)
+	}
+}
+
+func TestValidateConfig_DNSPersist01WithAllFields(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		fmt.Fprint(w, `{"newNonce":"","newAccount":"","newOrder":""}`)
+	}))
+	defer srv.Close()
+
+	c := New(nil, testLogger())
+	cfg, _ := json.Marshal(map[string]string{
+		"directory_url":           srv.URL,
+		"email":                   "test@example.com",
+		"challenge_type":          "dns-persist-01",
+		"dns_present_script":      "/bin/sh",
+		"dns_persist_issuer_domain": "letsencrypt.org",
+	})
+
+	err := c.ValidateConfig(context.Background(), cfg)
+	if err != nil {
+		t.Fatalf("expected DNS-PERSIST-01 to succeed, got: %v", err)
+	}
+
+	if c.config.DNSPersistIssuerDomain != "letsencrypt.org" {
+		t.Errorf("expected issuer domain to be set, got %s", c.config.DNSPersistIssuerDomain)
+	}
+}
+
+// --- Additional comprehensive tests ---
+
+func TestParseDERChain_MultipleChainCerts(t *testing.T) {
+	// Generate a complete chain: leaf -> intermediate -> root
+	rootKey, _ := generateTestKey()
+	intermediateKey, _ := generateTestKey()
+	leafKey, _ := generateTestKey()
+
+	// Root certificate (self-signed)
+	rootTemplate := x509.Certificate{
+		Subject:               generateTestName("Root CA"),
+		SerialNumber:          big.NewInt(1),
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().AddDate(20, 0, 0),
+		KeyUsage:              x509.KeyUsageCertSign,
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+	}
+	rootDER, _ := x509.CreateCertificate(nil, &rootTemplate, &rootTemplate, &rootKey.PublicKey, rootKey)
+
+	// Intermediate certificate (signed by root)
+	intermediateTemplate := x509.Certificate{
+		Subject:               generateTestName("Intermediate CA"),
+		SerialNumber:          big.NewInt(2),
+		NotBefore:             time.Now(),
+		NotAfter:              time.Now().AddDate(10, 0, 0),
+		KeyUsage:              x509.KeyUsageCertSign,
+		BasicConstraintsValid: true,
+		IsCA:                  true,
+		PublicKey:             &intermediateKey.PublicKey,
+	}
+	intermediateDER, _ := x509.CreateCertificate(nil, &intermediateTemplate, &rootTemplate, &intermediateKey.PublicKey, rootKey)
+
+	// Leaf certificate (signed by intermediate)
+	leafTemplate := x509.Certificate{
+		Subject:      generateTestName("leaf.example.com"),
+		SerialNumber: big.NewInt(100),
+		DNSNames:     []string{"leaf.example.com"},
+		NotBefore:    time.Now(),
+		NotAfter:     time.Now().AddDate(1, 0, 0),
+		KeyUsage:     x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
+		PublicKey:    &leafKey.PublicKey,
+	}
+	leafDER, _ := x509.CreateCertificate(nil, &leafTemplate, &intermediateTemplate, &leafKey.PublicKey, intermediateKey)
+
+	certPEM, chainPEM, serial, _, _, err := parseDERChain([][]byte{leafDER, intermediateDER, rootDER})
+	if err != nil {
+		t.Fatalf("parseDERChain failed: %v", err)
+	}
+
+	// Verify serial from leaf
+	if serial != "100" {
+		t.Errorf("expected serial '100', got: %s", serial)
+	}
+
+	// Verify chainPEM contains both intermediate and root
+	chainCount := strings.Count(chainPEM, "BEGIN CERTIFICATE")
+	if chainCount != 2 {
+		t.Errorf("expected 2 certs in chain, found %d", chainCount)
+	}
+
+	// Verify certPEM contains only the leaf
+	if !strings.Contains(certPEM, "BEGIN CERTIFICATE") {
+		t.Error("certPEM should contain certificate header")
+	}
+}
+
+func TestParseCSRPEM_WithTrailingWhitespace(t *testing.T) {
+	key, _ := generateTestKey()
+	csrTemplate := x509.CertificateRequest{
+		Subject:   generateTestName("test.example.com"),
+		PublicKey: &key.PublicKey,
+	}
+	csrDER, _ := x509.CreateCertificateRequest(nil, &csrTemplate, key)
+	csrPEM := string(pem.EncodeToMemory(&pem.Block{
+		Type:  "CERTIFICATE REQUEST",
+		Bytes: csrDER,
+	}))
+
+	// Add trailing whitespace and newlines
+	csrWithWhitespace := csrPEM + "\n\n  \n"
+
+	result, err := parseCSRPEM(csrWithWhitespace)
+	if err != nil {
+		t.Fatalf("parseCSRPEM should handle trailing whitespace, got: %v", err)
+	}
+
+	if len(result) == 0 {
+		t.Fatal("expected non-empty result")
+	}
+}
+
+func TestParseCSRPEM_MultipleCSRsInPEM(t *testing.T) {
+	key, _ := generateTestKey()
+	csrTemplate := x509.CertificateRequest{
+		Subject:   generateTestName("test.example.com"),
+		PublicKey: &key.PublicKey,
+	}
+	csrDER, _ := x509.CreateCertificateRequest(nil, &csrTemplate, key)
+	csrPEM := string(pem.EncodeToMemory(&pem.Block{
+		Type:  "CERTIFICATE REQUEST",
+		Bytes: csrDER,
+	}))
+
+	// pem.Decode only returns the first PEM block, so this tests that behavior
+	multiCSRPEM := csrPEM + "\n" + csrPEM
+
+	result, err := parseCSRPEM(multiCSRPEM)
+	if err != nil {
+		t.Fatalf("parseCSRPEM should handle multiple PEMs by decoding the first, got: %v", err)
+	}
+
+	if len(result) == 0 {
+		t.Fatal("expected non-empty result")
+	}
+}
+
+// --- Helper functions for tests ---
+
+func generateTestKey() (*ecdsa.PrivateKey, error) {
+	return ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+}
+
+func generateTestName(cn string) pkix.Name {
+	return pkix.Name{
+		CommonName:   cn,
+		Organization: []string{"Test Org"},
+		Country:      []string{"US"},
+	}
+}