build: update golangci-lint to v2.12.2 with new canonical v2 config

Pin golangci-lint to commit c0d3ddc9cf3faa61a4e378e879ece580256d76e5
(v2.12.2) in Dockerfile and script/bootstrap.

Replace .golangci.yml with a v2-schema migration of the canonical
config, produced with golangci-lint migrate (owner-authorized; the
same file becomes the new org-wide canonical via a prompts-repo PR).
Lint settings now live under linters.settings, so the lll, funlen,
cyclop, and dupl thresholds are actually applied. The deprecated
gomodguard linter is disabled in favor of gomodguard_v2, resolving
the v2.12 deprecation warning. Deliberate delta from the migrate
output: the gci formatter is not enabled because its default two-group
import ordering conflicts with the repo's stdlib/third-party/local
import style that script/fmt (gofmt + goimports) produces.

Fix all findings surfaced by the now-active thresholds:

- goconst: shared constants for repeated status, priority, and DNS
  fixture strings in watcher.go and the notify, state, and watcher
  tests
- dupl: consolidate duplicated ntfy/slack HTTP-error tests and
  SendNotification endpoint-error tests behind shared helpers
- lll: wrap long test table entries and comments; shorten one inline
  nolint justification

.golangci.yml

@@ -12,10 +12,10 @@ linters:
     - depguard         # Dependency allow/block lists
     - godot            # Requires comments to end with periods
     - wsl              # Deprecated, replaced by wsl_v5
+    - gomodguard       # Deprecated, replaced by gomodguard_v2
     - wrapcheck        # Too verbose for internal packages
     - varnamelen       # Short names like db, id are idiomatic Go
-
-linters-settings:
+  settings:
     lll:
       line-length: 88
     funlen:
@@ -25,8 +25,25 @@ linters-settings:
       max-complexity: 15
     dupl:
       threshold: 100
+  exclusions:
+    generated: lax
+    paths:
+      - third_party$
+      - builtin$
+      - examples$
 
 issues:
-  exclude-use-default: false
   max-issues-per-linter: 0
   max-same-issues: 0
+
+formatters:
+  enable:
+    - gofmt
+    - gofumpt
+    - goimports
+  exclusions:
+    generated: lax
+    paths:
+      - third_party$
+      - builtin$
+      - examples$

README.md

@@ -17,6 +17,26 @@ without requiring an external database.
 
 ---
 
+## No DNS mocking. Ever.
+
+**DNS is never mocked in this project — not in tests, not anywhere else.**
+No mock resolvers, no fake DNS servers, no stubbed lookups.
+
+dnswatcher's entire purpose is correct behavior against the real DNS.
+Tests exercise real iterative resolution against live nameservers by
+design; a test suite that passes against a mock proves nothing about the
+one thing this program exists to do.
+
+When live tests are flaky, that is a robustness problem, and it gets
+fixed with robustness: retries with backoff, querying multiple
+independent nameservers, longer timeouts — or explicit opt-in gating
+decided by the project owner. Never with mocks.
+
+Contributions that introduce mocked, faked, or stubbed DNS will be
+rejected.
+
+---
+
 ## Features
 
 ### DNS Domain Monitoring (Apex Domains)

TODO.md

@@ -26,8 +26,11 @@ confirm make check still passes.
 # Completed Steps
 
 - 2026-08-07: golangci-lint bumped to v2.12.2 (commit-pinned installs
-  in `Dockerfile` and `script/bootstrap`); fixed the resulting
-  `goconst` findings. `.golangci.yml` unchanged (canonical)
+  in `Dockerfile` and `script/bootstrap`); `.golangci.yml` migrated to
+  the v2 schema (owner-authorized; becomes the new org canonical), so
+  the lll/funlen/cyclop/dupl thresholds now apply; deprecated
+  `gomodguard` disabled in favor of `gomodguard_v2`; fixed the
+  resulting `goconst`, `dupl`, and `lll` findings
 - 2026-07-07 Adopted scripts-to-rule-them-all: `script/` entrypoints,
   Makefile shims, README Entrypoints section
 - 2026-02-20: iterative DNS resolver implemented; tests made hermetic

internal/config/classify_test.go

@@ -17,13 +17,33 @@ func TestClassifyDNSName(t *testing.T) {
 	}{
 		{name: "apex domain simple", input: "example.com", want: config.DNSNameTypeDomain},
 		{name: "hostname simple", input: "www.example.com", want: config.DNSNameTypeHostname},
-		{name: "apex domain multi-part TLD", input: "example.co.uk", want: config.DNSNameTypeDomain},
-		{name: "hostname multi-part TLD", input: "api.example.co.uk", want: config.DNSNameTypeHostname},
+		{
+			name:  "apex domain multi-part TLD",
+			input: "example.co.uk",
+			want:  config.DNSNameTypeDomain,
+		},
+		{
+			name:  "hostname multi-part TLD",
+			input: "api.example.co.uk",
+			want:  config.DNSNameTypeHostname,
+		},
 		{name: "public suffix itself", input: "co.uk", wantErr: true},
 		{name: "empty string", input: "", wantErr: true},
-		{name: "deeply nested hostname", input: "a.b.c.example.com", want: config.DNSNameTypeHostname},
-		{name: "trailing dot stripped", input: "example.com.", want: config.DNSNameTypeDomain},
-		{name: "uppercase normalized", input: "WWW.Example.COM", want: config.DNSNameTypeHostname},
+		{
+			name:  "deeply nested hostname",
+			input: "a.b.c.example.com",
+			want:  config.DNSNameTypeHostname,
+		},
+		{
+			name:  "trailing dot stripped",
+			input: "example.com.",
+			want:  config.DNSNameTypeDomain,
+		},
+		{
+			name:  "uppercase normalized",
+			input: "WWW.Example.COM",
+			want:  config.DNSNameTypeHostname,
+		},
 	}
 
 	for _, tt := range tests {

internal/notify/delivery_test.go

@@ -25,18 +25,20 @@ const (
 	colorDefault = "#6c757d"
 )
 
-// Priority and fixture values shared across tests.
+// Priority strings used across multiple tests.
 const (
 	prioError   = "error"
 	prioWarning = "warning"
-	prioInfo    = "info"
 	prioSuccess = "success"
+	prioInfo    = "info"
 	prioUnknown = "unknown"
-	ntfyUrgent  = "urgent"
-	ntfyDefault = "default"
-	testHost    = "example.com"
+	prioDefault = "default"
+	prioUrgent  = "urgent"
 )
 
+// testHost is the hostname used in request construction tests.
+const testHost = "example.com"
+
 // errSimulated is a static error for transport failures.
 var errSimulated = errors.New("simulated transport failure")
 
@@ -113,13 +115,13 @@ func TestNtfyPriority(t *testing.T) {
 		input string
 		want  string
 	}{
-		{prioError, ntfyUrgent},
+		{prioError, prioUrgent},
 		{prioWarning, "high"},
-		{prioSuccess, ntfyDefault},
+		{prioSuccess, prioDefault},
 		{prioInfo, "low"},
-		{"", ntfyDefault},
-		{prioUnknown, ntfyDefault},
-		{"critical", ntfyDefault},
+		{"", prioDefault},
+		{prioUnknown, prioDefault},
+		{"critical", prioDefault},
 	}
 
 	for _, tc := range cases {
@@ -301,10 +303,10 @@ func TestSendNtfyHeaders(t *testing.T) {
 		)
 	}
 
-	if captured.priority != ntfyUrgent {
+	if captured.priority != prioUrgent {
 		t.Errorf(
 			"Priority header = %q, want %q",
-			captured.priority, ntfyUrgent,
+			captured.priority, prioUrgent,
 		)
 	}
 
@@ -323,9 +325,9 @@ func TestSendNtfyAllPriorities(t *testing.T) {
 		input string
 		want  string
 	}{
-		{prioError, ntfyUrgent},
+		{prioError, prioUrgent},
 		{prioWarning, "high"},
-		{prioSuccess, ntfyDefault},
+		{prioSuccess, prioDefault},
 		{prioInfo, "low"},
 	}
 
@@ -368,56 +370,69 @@ func TestSendNtfyAllPriorities(t *testing.T) {
 	}
 }
 
-func TestSendNtfyClientError(t *testing.T) {
-	t.Parallel()
+// assertSendStatusError verifies that send returns an error
+// wrapping wantErr when the server responds with status.
+func assertSendStatusError(
+	t *testing.T,
+	status int,
+	wantErr error,
+	send func(*notify.Service, *url.URL) error,
+) {
+	t.Helper()
 
 	srv := httptest.NewServer(
 		http.HandlerFunc(
 			func(w http.ResponseWriter, _ *http.Request) {
-				w.WriteHeader(http.StatusForbidden)
+				w.WriteHeader(status)
 			}),
 	)
 	defer srv.Close()
 
 	svc := notify.NewTestService(srv.Client().Transport)
-	topicURL, _ := url.Parse(srv.URL)
+	target, _ := url.Parse(srv.URL)
 
-	err := svc.SendNtfy(
-		context.Background(), topicURL, "t", "m", "info",
-	)
+	err := send(svc, target)
 	if err == nil {
-		t.Fatal("expected error for 403 response")
+		t.Fatalf("expected error for %d response", status)
 	}
 
-	if !errors.Is(err, notify.ErrNtfyFailed) {
-		t.Errorf("error = %v, want ErrNtfyFailed", err)
+	if !errors.Is(err, wantErr) {
+		t.Errorf("error = %v, want %v", err, wantErr)
 	}
 }
 
+func sendNtfyInfo(
+	svc *notify.Service, target *url.URL,
+) error {
+	return svc.SendNtfy(
+		context.Background(), target, "t", "m", prioInfo,
+	)
+}
+
+func sendSlackInfo(
+	svc *notify.Service, target *url.URL,
+) error {
+	return svc.SendSlack(
+		context.Background(), target, "t", "m", prioInfo,
+	)
+}
+
+func TestSendNtfyClientError(t *testing.T) {
+	t.Parallel()
+
+	assertSendStatusError(
+		t, http.StatusForbidden,
+		notify.ErrNtfyFailed, sendNtfyInfo,
+	)
+}
+
 func TestSendNtfyServerError(t *testing.T) {
 	t.Parallel()
 
-	srv := httptest.NewServer(
-		http.HandlerFunc(
-			func(w http.ResponseWriter, _ *http.Request) {
-				w.WriteHeader(http.StatusInternalServerError)
-			}),
+	assertSendStatusError(
+		t, http.StatusInternalServerError,
+		notify.ErrNtfyFailed, sendNtfyInfo,
 	)
-	defer srv.Close()
-
-	svc := notify.NewTestService(srv.Client().Transport)
-	topicURL, _ := url.Parse(srv.URL)
-
-	err := svc.SendNtfy(
-		context.Background(), topicURL, "t", "m", "info",
-	)
-	if err == nil {
-		t.Fatal("expected error for 500 response")
-	}
-
-	if !errors.Is(err, notify.ErrNtfyFailed) {
-		t.Errorf("error = %v, want ErrNtfyFailed", err)
-	}
 }
 
 func TestSendNtfySuccess(t *testing.T) {
@@ -618,53 +633,19 @@ func TestSendSlackAllColors(t *testing.T) {
 func TestSendSlackClientError(t *testing.T) {
 	t.Parallel()
 
-	srv := httptest.NewServer(
-		http.HandlerFunc(
-			func(w http.ResponseWriter, _ *http.Request) {
-				w.WriteHeader(http.StatusBadRequest)
-			}),
+	assertSendStatusError(
+		t, http.StatusBadRequest,
+		notify.ErrSlackFailed, sendSlackInfo,
 	)
-	defer srv.Close()
-
-	svc := notify.NewTestService(srv.Client().Transport)
-	webhookURL, _ := url.Parse(srv.URL)
-
-	err := svc.SendSlack(
-		context.Background(), webhookURL, "t", "m", "info",
-	)
-	if err == nil {
-		t.Fatal("expected error for 400 response")
-	}
-
-	if !errors.Is(err, notify.ErrSlackFailed) {
-		t.Errorf("error = %v, want ErrSlackFailed", err)
-	}
 }
 
 func TestSendSlackServerError(t *testing.T) {
 	t.Parallel()
 
-	srv := httptest.NewServer(
-		http.HandlerFunc(
-			func(w http.ResponseWriter, _ *http.Request) {
-				w.WriteHeader(http.StatusBadGateway)
-			}),
+	assertSendStatusError(
+		t, http.StatusBadGateway,
+		notify.ErrSlackFailed, sendSlackInfo,
 	)
-	defer srv.Close()
-
-	svc := notify.NewTestService(srv.Client().Transport)
-	webhookURL, _ := url.Parse(srv.URL)
-
-	err := svc.SendSlack(
-		context.Background(), webhookURL, "t", "m", "error",
-	)
-	if err == nil {
-		t.Fatal("expected error for 502 response")
-	}
-
-	if !errors.Is(err, notify.ErrSlackFailed) {
-		t.Errorf("error = %v, want ErrSlackFailed", err)
-	}
 }
 
 func TestSendSlackNetworkError(t *testing.T) {
@@ -989,74 +970,62 @@ func TestSendNotificationMattermostOnly(t *testing.T) {
 	}
 }
 
-func TestSendNotificationNtfyError(t *testing.T) {
-	t.Parallel()
+// assertSendNotificationTolerates verifies SendNotification
+// neither panics nor blocks when the endpoint configured by
+// setURL responds with status.
+func assertSendNotificationTolerates(
+	t *testing.T,
+	status int,
+	priority string,
+	setURL func(*notify.Service, *url.URL),
+) {
+	t.Helper()
 
 	srv := httptest.NewServer(
 		http.HandlerFunc(
 			func(w http.ResponseWriter, _ *http.Request) {
-				w.WriteHeader(http.StatusInternalServerError)
+				w.WriteHeader(status)
 			}),
 	)
 	defer srv.Close()
 
-	ntfyURL, _ := url.Parse(srv.URL)
+	target, _ := url.Parse(srv.URL)
 
 	svc := notify.NewTestService(http.DefaultTransport)
-	svc.SetNtfyURL(ntfyURL)
+	setURL(svc, target)
 
-	// Should not panic or block.
 	svc.SendNotification(
-		context.Background(), "t", "m", "error",
+		context.Background(), "t", "m", priority,
 	)
 
 	time.Sleep(100 * time.Millisecond)
 }
 
+func TestSendNotificationNtfyError(t *testing.T) {
+	t.Parallel()
+
+	assertSendNotificationTolerates(
+		t, http.StatusInternalServerError, prioError,
+		(*notify.Service).SetNtfyURL,
+	)
+}
+
 func TestSendNotificationSlackError(t *testing.T) {
 	t.Parallel()
 
-	srv := httptest.NewServer(
-		http.HandlerFunc(
-			func(w http.ResponseWriter, _ *http.Request) {
-				w.WriteHeader(http.StatusForbidden)
-			}),
+	assertSendNotificationTolerates(
+		t, http.StatusForbidden, prioError,
+		(*notify.Service).SetSlackWebhookURL,
 	)
-	defer srv.Close()
-
-	slackURL, _ := url.Parse(srv.URL)
-
-	svc := notify.NewTestService(http.DefaultTransport)
-	svc.SetSlackWebhookURL(slackURL)
-
-	svc.SendNotification(
-		context.Background(), "t", "m", "error",
-	)
-
-	time.Sleep(100 * time.Millisecond)
 }
 
 func TestSendNotificationMattermostError(t *testing.T) {
 	t.Parallel()
 
-	srv := httptest.NewServer(
-		http.HandlerFunc(
-			func(w http.ResponseWriter, _ *http.Request) {
-				w.WriteHeader(http.StatusBadGateway)
-			}),
+	assertSendNotificationTolerates(
+		t, http.StatusBadGateway, prioWarning,
+		(*notify.Service).SetMattermostWebhookURL,
 	)
-	defer srv.Close()
-
-	mmURL, _ := url.Parse(srv.URL)
-
-	svc := notify.NewTestService(http.DefaultTransport)
-	svc.SetMattermostWebhookURL(mmURL)
-
-	svc.SendNotification(
-		context.Background(), "t", "m", "warning",
-	)
-
-	time.Sleep(100 * time.Millisecond)
 }
 
 // ── SlackPayload JSON marshaling ──────────────────────────

internal/notify/retry.go

@@ -69,7 +69,7 @@ func (rc RetryConfig) backoff(attempt int) time.Duration {
 	lo := raw * (1 - jitterFraction)
 	hi := raw * (1 + jitterFraction)
 
-	jittered := lo + rand.Float64()*(hi-lo) //nolint:gosec // jitter does not need crypto/rand
+	jittered := lo + rand.Float64()*(hi-lo) //nolint:gosec // jitter needs no crypto/rand
 
 	return time.Duration(jittered)
 }

internal/state/state_test.go

@@ -223,7 +223,8 @@ func TestSaveLoadRoundTrip_Ports(t *testing.T) {
 	}
 }
 
-// TestSaveLoadRoundTrip_Certificates verifies certificate data survives a save/load cycle.
+// TestSaveLoadRoundTrip_Certificates verifies certificate data
+// survives a save/load cycle.
 func TestSaveLoadRoundTrip_Certificates(t *testing.T) {
 	t.Parallel()
 
@@ -1072,7 +1073,8 @@ func TestConcurrentGetSet(t *testing.T) {
 	wg.Wait()
 }
 
-// runConcurrentOps performs a series of get/set/delete operations for concurrency testing.
+// runConcurrentOps performs a series of get/set/delete
+// operations for concurrency testing.
 func runConcurrentOps(s *state.State, key string, now time.Time) {
 	const iterations = 50
 

internal/watcher/watcher.go

@@ -26,8 +26,11 @@ const tlsPort = 443
 // hoursPerDay converts days to hours for duration calculations.
 const hoursPerDay = 24
 
-// statusError is the status value recorded for failed checks.
-const statusError = "error"
+// Status values recorded for nameserver and certificate checks.
+const (
+	statusOK    = "ok"
+	statusError = "error"
+)
 
 // Params contains dependencies for Watcher.
 type Params struct {
@@ -347,7 +350,7 @@ func buildHostnameState(
 	for ns, recs := range records {
 		hs.RecordsByNameserver[ns] = &state.NameserverRecordState{
 			Records:     recs,
-			Status:      "ok",
+			Status:      statusOK,
 			LastChecked: now,
 		}
 	}
@@ -405,7 +408,7 @@ func (w *Watcher) detectNSDisappearances(
 	current map[string]map[string][]string,
 ) {
 	for ns, prevNS := range prev.RecordsByNameserver {
-		if _, ok := current[ns]; ok || prevNS.Status != "ok" {
+		if _, ok := current[ns]; ok || prevNS.Status != statusOK {
 			continue
 		}
 
@@ -708,7 +711,7 @@ func (w *Watcher) handleTLSError(
 	now time.Time,
 	err error,
 ) {
-	if hasPrev && !w.firstRun && prev.Status == "ok" {
+	if hasPrev && !w.firstRun && prev.Status == statusOK {
 		msg := fmt.Sprintf(
 			"Host: %s\nIP: %s\nError: %s",
 			hostname, ip, err,
@@ -751,7 +754,7 @@ func (w *Watcher) handleTLSSuccess(
 			Issuer:                  cert.Issuer,
 			NotAfter:                cert.NotAfter,
 			SubjectAlternativeNames: cert.SubjectAlternativeNames,
-			Status:                  "ok",
+			Status:                  statusOK,
 			LastChecked:             now,
 		},
 	)