test(service): add tests for IP ban update edge cases

Add integration tests for `IPBanService.Update` to verify:
- Reactivating an expired ban correctly detects overlaps with existing active bans.
- Explicitly clearing the `expires_at` field (setting to null) works as expected.

internal/service/ip_ban_test.go

@@ -1,7 +1,14 @@
 package service
 
 import (
+	"context"
+	"errors"
 	"testing"
+	"time"
+
+	"github.com/ez-api/ez-api/internal/model"
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
 )
 
 func TestNormalizeCIDR_IPv4Address(t *testing.T) {
@@ -150,3 +157,82 @@ func TestCIDROverlaps_InvalidCIDR(t *testing.T) {
 		t.Error("expected no overlap with invalid CIDR")
 	}
 }
+
+func TestIPBanService_Update_ReactivateOverlap(t *testing.T) {
+	t.Parallel()
+
+	db, err := gorm.Open(sqlite.Open("file:"+t.Name()+"?mode=memory&cache=shared"), &gorm.Config{})
+	if err != nil {
+		t.Fatalf("open sqlite: %v", err)
+	}
+	if err := db.AutoMigrate(&model.IPBan{}); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+
+	active := model.IPBan{CIDR: "10.0.0.0/24", Status: model.IPBanStatusActive}
+	if err := db.Create(&active).Error; err != nil {
+		t.Fatalf("create active ban: %v", err)
+	}
+
+	expired := model.IPBan{CIDR: "10.0.0.128/25", Status: model.IPBanStatusExpired}
+	if err := db.Create(&expired).Error; err != nil {
+		t.Fatalf("create expired ban: %v", err)
+	}
+
+	svc := NewIPBanService(db, nil)
+	_, err = svc.Update(context.Background(), expired.ID, UpdateIPBanRequest{
+		Status: func() *string {
+			s := model.IPBanStatusActive
+			return &s
+		}(),
+	})
+	if !errors.Is(err, ErrCIDROverlap) {
+		t.Fatalf("expected overlap error, got %v", err)
+	}
+
+	var reloaded model.IPBan
+	if err := db.First(&reloaded, expired.ID).Error; err != nil {
+		t.Fatalf("reload expired ban: %v", err)
+	}
+	if reloaded.Status != model.IPBanStatusExpired {
+		t.Fatalf("expected status to remain expired, got %s", reloaded.Status)
+	}
+}
+
+func TestIPBanService_Update_ClearExpiresAt(t *testing.T) {
+	t.Parallel()
+
+	db, err := gorm.Open(sqlite.Open("file:"+t.Name()+"?mode=memory&cache=shared"), &gorm.Config{})
+	if err != nil {
+		t.Fatalf("open sqlite: %v", err)
+	}
+	if err := db.AutoMigrate(&model.IPBan{}); err != nil {
+		t.Fatalf("migrate: %v", err)
+	}
+
+	exp := time.Now().Add(time.Hour).Unix()
+	ban := model.IPBan{
+		CIDR:      "192.168.1.1/32",
+		Status:    model.IPBanStatusActive,
+		ExpiresAt: &exp,
+	}
+	if err := db.Create(&ban).Error; err != nil {
+		t.Fatalf("create ban: %v", err)
+	}
+
+	svc := NewIPBanService(db, nil)
+	if _, err := svc.Update(context.Background(), ban.ID, UpdateIPBanRequest{
+		ExpiresAt:    nil,
+		ExpiresAtSet: true,
+	}); err != nil {
+		t.Fatalf("update expires_at: %v", err)
+	}
+
+	var reloaded model.IPBan
+	if err := db.First(&reloaded, ban.ID).Error; err != nil {
+		t.Fatalf("reload ban: %v", err)
+	}
+	if reloaded.ExpiresAt != nil {
+		t.Fatalf("expected expires_at to be cleared, got %v", *reloaded.ExpiresAt)
+	}
+}