test(api): integration coverage — brevo ledger webhook + status endpoint (toward 100%)

Adds REAL-DB integration tests for two handlers that previously had ONLY
sqlmock (unit) coverage, closing integration gaps flagged in
INTEGRATION-COVERAGE-PLAN-2026-06-04 §2.1.

brevo_webhook_realdb_integration_test.go — POST /webhooks/brevo/:secret,
the rule-12 email truth surface. Seeds real forwarder_sent rows, POSTs
synthetic Brevo events, reads back via the production
LookupForwarderSentByProviderID helper. Proves the SQL is CORRECT (not
just "issued"): delivered overwrites classification + stamps delivered_at;
each non-delivered event maps to its terminal class leaving delivered_at
NULL; the bug-bash #6 terminal-class guard preserves bounced_hard/soft/
rejected/complaint/unsubscribed against a LATE out-of-order 'delivered'
while still upgrading deferred/success; GREATEST delivered_at is monotonic
on Brevo retries (idempotent); an orphan messageId is a 200 no-op that
creates no row. Testable today despite the unvalidated-Brevo-sender block
(synthetic payload, not a live send).

status_realdb_integration_test.go — GET /api/v1/status. Seeds real
service_components + uptime_samples and asserts the computed payload through
a Fiber app on real DB + real Redis: operational (all-healthy) vs down
(recent unhealthy probe), empty-DB clean state (never 500), the 60s
cache.GetOrSet round-trip (second request served from Redis, cache-bust
surfaces a mid-flight DB mutation), and the nil-Redis DB-fallback path.

No production code changed. Integration coverage (handlers, -coverpkg=./...):
78.6% -> 78.7%; status.go computeOne 86.0% -> 89.5%. The pre-existing local
TestQueue_CredIssueError_FallsBackToLegacyOpen 503 (NATS unreachable
locally) is unchanged and unrelated.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: mastermanas805

internal/handlers/brevo_webhook_realdb_integration_test.go

@@ -0,0 +1,298 @@
+package handlers_test
+
+// brevo_webhook_realdb_integration_test.go — REAL-DB integration coverage for
+// the Brevo transactional-delivery receiver at POST /webhooks/brevo/:secret.
+//
+// WHY THIS FILE EXISTS (integration-coverage wave 2, 2026-06-04):
+//
+// brevo_webhook_test.go drives the same handler entirely through sqlmock — it
+// asserts the handler ISSUES the right SQL string, but it never proves the SQL
+// is CORRECT against a real Postgres schema. The rule-12 email truth surface
+// (forwarder_sent.classification + delivered_at) is only as trustworthy as the
+// actual UPDATE behaviour:
+//
+//   * the delivered path uses COALESCE(GREATEST(delivered_at, NOW()), NOW())
+//     — a sqlmock can't tell us whether that expression even parses against
+//     the real column type, let alone that it's monotonic.
+//   * the bug-bash #6 terminal-class guard
+//     (classification NOT IN (bounced_hard, bounced_soft, rejected, complaint,
+//     unsubscribed)) is a row-state predicate — sqlmock returns whatever rows
+//     we tell it to; only a real row can prove a late 'delivered' does NOT
+//     clobber a recorded 'bounced_hard'.
+//
+// These tests seed a real forwarder_sent row, POST a synthetic Brevo event
+// (the same shape Brevo emits — NOT a live send, so the unvalidated-sender
+// production block is irrelevant), and read the row back via the production
+// LookupForwarderSentByProviderID helper to assert the ledger overwrite.
+//
+// Tests are skipped (not failed) when TEST_DATABASE_URL is unreachable so the
+// hermetic `-short` gate stays green; CI supplies the DB and runs them for
+// real.
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"net/http"
+	"testing"
+	"time"
+
+	"github.com/gofiber/fiber/v2"
+	"github.com/google/uuid"
+
+	"instant.dev/internal/config"
+	"instant.dev/internal/handlers"
+	"instant.dev/internal/testhelpers"
+)
+
+// brevoTxRealApp builds a Fiber app with ONLY the transactional-delivery
+// receiver mounted, wired to the supplied real *sql.DB. Mirrors the production
+// ErrorHandler short-circuit so respondError envelopes pass through unchanged.
+func brevoTxRealApp(t *testing.T, db *sql.DB) *fiber.App {
+	t.Helper()
+	h := handlers.NewBrevoTransactionalWebhookHandler(db, &config.Config{BrevoWebhookSecret: testBrevoTxSecret})
+	app := fiber.New(fiber.Config{
+		ErrorHandler: func(c *fiber.Ctx, err error) error {
+			if errors.Is(err, handlers.ErrResponseWritten) {
+				return nil
+			}
+			return fiber.DefaultErrorHandler(c, err)
+		},
+	})
+	app.Post("/webhooks/brevo/:secret", h.Receive)
+	return app
+}
+
+// seedForwarderSent inserts a forwarder_sent row with the given provider_id +
+// initial classification and returns the audit_id. The row carries
+// provider='brevo' so the receiver's (provider, provider_id) lookup matches.
+func seedForwarderSent(t *testing.T, db *sql.DB, providerID, classification string) string {
+	t.Helper()
+	auditID := uuid.NewString()
+	_, err := db.ExecContext(context.Background(), `
+		INSERT INTO forwarder_sent (audit_id, provider, provider_id, recipient, template_kind, classification)
+		VALUES ($1, 'brevo', $2, 'u***@example.com', 'anon.expiry_warning', $3)
+	`, auditID, providerID, classification)
+	if err != nil {
+		t.Fatalf("seedForwarderSent: %v", err)
+	}
+	return auditID
+}
+
+// ── 1. delivered event overwrites classification AND stamps delivered_at ──
+
+func TestBrevoTxWebhook_RealDB_DeliveredOverwritesLedger(t *testing.T) {
+	db, cleanup := testhelpers.SetupTestDB(t)
+	defer cleanup()
+
+	providerID := "msg-realdb-" + uuid.NewString()[:8]
+	seedForwarderSent(t, db, providerID, "success") // worker's API-acceptance state
+
+	app := brevoTxRealApp(t, db)
+	body := `{"event":"delivered","email":"u@example.com","message-id":"` + providerID + `","subject":"Welcome"}`
+	resp := postBrevoTx(t, app, testBrevoTxSecret, body)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status = %d; want 200", resp.StatusCode)
+	}
+
+	row, err := handlers.LookupForwarderSentByProviderID(context.Background(), db, providerID)
+	if err != nil {
+		t.Fatalf("LookupForwarderSentByProviderID: %v", err)
+	}
+	if row.Classification != "delivered" {
+		t.Errorf("classification = %q; want delivered (rule-12 truth surface must overwrite the worker's 'success')", row.Classification)
+	}
+	if row.DeliveredAt == nil {
+		t.Error("delivered_at must be stamped on a 'delivered' event; got nil")
+	}
+}
+
+// ── 2. each non-delivered event overwrites classification, leaves delivered_at NULL ──
+
+func TestBrevoTxWebhook_RealDB_FailureEventsOverwriteClassification(t *testing.T) {
+	db, cleanup := testhelpers.SetupTestDB(t)
+	defer cleanup()
+
+	cases := []struct {
+		event     string
+		wantClass string
+	}{
+		{"hard_bounce", "bounced_hard"},
+		{"soft_bounce", "bounced_soft"},
+		{"blocked", "rejected"},
+		{"complaint", "complaint"},
+		{"spam", "complaint"}, // alias → complaint
+		{"deferred", "deferred"},
+		{"unsubscribed", "unsubscribed"},
+		{"error", "error"},
+	}
+	app := brevoTxRealApp(t, db)
+	for _, c := range cases {
+		t.Run(c.event, func(t *testing.T) {
+			providerID := "msg-fail-" + c.event + "-" + uuid.NewString()[:8]
+			seedForwarderSent(t, db, providerID, "success")
+
+			body := `{"event":"` + c.event + `","email":"u@example.com","message-id":"` + providerID + `","reason":"mailbox full"}`
+			resp := postBrevoTx(t, app, testBrevoTxSecret, body)
+			if resp.StatusCode != http.StatusOK {
+				t.Fatalf("status = %d; want 200", resp.StatusCode)
+			}
+
+			row, err := handlers.LookupForwarderSentByProviderID(context.Background(), db, providerID)
+			if err != nil {
+				t.Fatalf("Lookup: %v", err)
+			}
+			if row.Classification != c.wantClass {
+				t.Errorf("classification = %q; want %q", row.Classification, c.wantClass)
+			}
+			// Only the 'delivered' event ever stamps delivered_at.
+			if row.DeliveredAt != nil {
+				t.Errorf("delivered_at must stay NULL on a %q event; got %v", c.event, row.DeliveredAt)
+			}
+		})
+	}
+}
+
+// ── 3. bug-bash #6 terminal-class guard: a LATE 'delivered' must NOT clobber a
+//       recorded 'bounced_hard'. This is the #6 guard area the brief calls out
+//       — it can ONLY be proven against a real row (sqlmock can't enforce the
+//       NOT IN row-state predicate).
+
+func TestBrevoTxWebhook_RealDB_LateDeliveredDoesNotClobberHardBounce(t *testing.T) {
+	db, cleanup := testhelpers.SetupTestDB(t)
+	defer cleanup()
+
+	providerID := "msg-terminal-" + uuid.NewString()[:8]
+	// The row is ALREADY terminal — a hard bounce was recorded first.
+	seedForwarderSent(t, db, providerID, "bounced_hard")
+
+	app := brevoTxRealApp(t, db)
+	// Out-of-order: Brevo's SMTP-accept 'delivered' arrives AFTER the bounce.
+	body := `{"event":"delivered","email":"u@example.com","message-id":"` + providerID + `"}`
+	resp := postBrevoTx(t, app, testBrevoTxSecret, body)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status = %d; want 200", resp.StatusCode)
+	}
+
+	row, err := handlers.LookupForwarderSentByProviderID(context.Background(), db, providerID)
+	if err != nil {
+		t.Fatalf("Lookup: %v", err)
+	}
+	if row.Classification != "bounced_hard" {
+		t.Errorf("terminal class clobbered: classification = %q; want bounced_hard preserved (bug-bash #6)", row.Classification)
+	}
+	if row.DeliveredAt != nil {
+		t.Errorf("delivered_at must NOT be stamped when the terminal class is preserved; got %v", row.DeliveredAt)
+	}
+}
+
+// ── 3b. the guard also preserves the OTHER terminal classes, and a 'delivered'
+//        DOES win when the prior state is a non-terminal 'deferred'. This pins
+//        the exact NOT IN set so a future edit that drops a class from the
+//        guard fails here.
+
+func TestBrevoTxWebhook_RealDB_TerminalGuardSetIsExact(t *testing.T) {
+	db, cleanup := testhelpers.SetupTestDB(t)
+	defer cleanup()
+	app := brevoTxRealApp(t, db)
+
+	cases := []struct {
+		name           string
+		seedClass      string
+		wantClassAfter string
+		wantDelivered  bool
+	}{
+		// Terminal classes: a late 'delivered' is a no-op on classification.
+		{"hard_bounce_preserved", "bounced_hard", "bounced_hard", false},
+		{"soft_bounce_preserved", "bounced_soft", "bounced_soft", false},
+		{"rejected_preserved", "rejected", "rejected", false},
+		{"complaint_preserved", "complaint", "complaint", false},
+		{"unsubscribed_preserved", "unsubscribed", "unsubscribed", false},
+		// Non-terminal classes: a 'delivered' SHOULD win (deferred is transient;
+		// 'success' is the worker's API-acceptance placeholder).
+		{"deferred_upgraded", "deferred", "delivered", true},
+		{"success_upgraded", "success", "delivered", true},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			providerID := "msg-guard-" + c.name + "-" + uuid.NewString()[:8]
+			seedForwarderSent(t, db, providerID, c.seedClass)
+
+			body := `{"event":"delivered","email":"u@example.com","message-id":"` + providerID + `"}`
+			resp := postBrevoTx(t, app, testBrevoTxSecret, body)
+			if resp.StatusCode != http.StatusOK {
+				t.Fatalf("status = %d; want 200", resp.StatusCode)
+			}
+			row, err := handlers.LookupForwarderSentByProviderID(context.Background(), db, providerID)
+			if err != nil {
+				t.Fatalf("Lookup: %v", err)
+			}
+			if row.Classification != c.wantClassAfter {
+				t.Errorf("seed=%q: classification = %q; want %q", c.seedClass, row.Classification, c.wantClassAfter)
+			}
+			if (row.DeliveredAt != nil) != c.wantDelivered {
+				t.Errorf("seed=%q: delivered_at set = %v; want %v", c.seedClass, row.DeliveredAt != nil, c.wantDelivered)
+			}
+		})
+	}
+}
+
+// ── 4. idempotency: a re-delivery of the same 'delivered' event is a no-op on
+//        the value side and does NOT push delivered_at backwards (GREATEST).
+
+func TestBrevoTxWebhook_RealDB_DeliveredIsIdempotent(t *testing.T) {
+	db, cleanup := testhelpers.SetupTestDB(t)
+	defer cleanup()
+
+	providerID := "msg-idem-" + uuid.NewString()[:8]
+	seedForwarderSent(t, db, providerID, "success")
+	app := brevoTxRealApp(t, db)
+	body := `{"event":"delivered","email":"u@example.com","message-id":"` + providerID + `"}`
+
+	// First delivery stamps delivered_at.
+	if resp := postBrevoTx(t, app, testBrevoTxSecret, body); resp.StatusCode != http.StatusOK {
+		t.Fatalf("first POST status = %d; want 200", resp.StatusCode)
+	}
+	first, err := handlers.LookupForwarderSentByProviderID(context.Background(), db, providerID)
+	if err != nil || first.DeliveredAt == nil {
+		t.Fatalf("after first delivery: row=%+v err=%v", first, err)
+	}
+	firstTS := *first.DeliveredAt
+
+	// A re-delivery (Brevo retry) must keep classification + must not move
+	// delivered_at backwards (GREATEST). It may bump forward by sub-second; we
+	// assert it never regresses.
+	time.Sleep(10 * time.Millisecond)
+	if resp := postBrevoTx(t, app, testBrevoTxSecret, body); resp.StatusCode != http.StatusOK {
+		t.Fatalf("second POST status = %d; want 200", resp.StatusCode)
+	}
+	second, err := handlers.LookupForwarderSentByProviderID(context.Background(), db, providerID)
+	if err != nil {
+		t.Fatalf("Lookup after re-delivery: %v", err)
+	}
+	if second.Classification != "delivered" {
+		t.Errorf("classification after re-delivery = %q; want delivered", second.Classification)
+	}
+	if second.DeliveredAt == nil || second.DeliveredAt.Before(firstTS) {
+		t.Errorf("delivered_at regressed: first=%v second=%v (GREATEST must keep it monotonic)", firstTS, second.DeliveredAt)
+	}
+}
+
+// ── 5. unknown messageId (no matching row) → 200 matched:false, NO row created.
+
+func TestBrevoTxWebhook_RealDB_UnknownMessageIDIsNoOp(t *testing.T) {
+	db, cleanup := testhelpers.SetupTestDB(t)
+	defer cleanup()
+	app := brevoTxRealApp(t, db)
+
+	orphanID := "msg-orphan-" + uuid.NewString()[:8]
+	body := `{"event":"delivered","email":"u@example.com","message-id":"` + orphanID + `"}`
+	resp := postBrevoTx(t, app, testBrevoTxSecret, body)
+	if resp.StatusCode != http.StatusOK {
+		t.Fatalf("status = %d; want 200 (Brevo retries on non-2xx — orphans must NOT amplify retry)", resp.StatusCode)
+	}
+	// The handler must NEVER INSERT a ledger row for an orphan event.
+	if _, err := handlers.LookupForwarderSentByProviderID(context.Background(), db, orphanID); !errors.Is(err, sql.ErrNoRows) {
+		t.Errorf("orphan messageId must leave no forwarder_sent row; lookup err = %v (want sql.ErrNoRows)", err)
+	}
+}