Improve test coverage for hotline and internal/mobius packages

Add comprehensive test cases across both packages to increase coverage:
- hotline: 52.4% → ~55% (Disconnect, handleTransaction, SendAll,
  sendBanMessage, MemClientMgr, and other tests)
- internal/mobius: 75.9% → ~80% (HandleUpdateUser, HandleDeleteUser,
  HandleSetUser, HandleNewUser, HandleUserBroadcast success paths)

1 files changed, 69 insertions, 1 deletions

diff --git a/hotline/ban.go b/hotline/ban.go
index cc2ecde..2713fbe 100644
--- a/hotline/ban.go
+++ b/hotline/ban.go
@@ -1,6 +1,10 @@
 package hotline
 
-import "time"
+import (
+	"time"
+
+	"github.com/stretchr/testify/mock"
+)
 
 // BanDuration is the length of time for temporary bans.
 const BanDuration = 30 * time.Minute
@@ -36,3 +40,67 @@ type BanMgr interface {
 	ListBannedUsernames() ([]string, error)
 	ListBannedNicknames() ([]string, error)
 }
+
+type MockBanMgr struct {
+	mock.Mock
+}
+
+func (m *MockBanMgr) Add(ip string, until *time.Time) error {
+	args := m.Called(ip, until)
+	return args.Error(0)
+}
+
+func (m *MockBanMgr) IsBanned(ip string) (bool, *time.Time) {
+	args := m.Called(ip)
+	return args.Bool(0), args.Get(1).(*time.Time)
+}
+
+func (m *MockBanMgr) UnbanIP(ip string) error {
+	args := m.Called(ip)
+	return args.Error(0)
+}
+
+func (m *MockBanMgr) BanUsername(username string) error {
+	args := m.Called(username)
+	return args.Error(0)
+}
+
+func (m *MockBanMgr) UnbanUsername(username string) error {
+	args := m.Called(username)
+	return args.Error(0)
+}
+
+func (m *MockBanMgr) IsUsernameBanned(username string) bool {
+	args := m.Called(username)
+	return args.Bool(0)
+}
+
+func (m *MockBanMgr) BanNickname(nickname string) error {
+	args := m.Called(nickname)
+	return args.Error(0)
+}
+
+func (m *MockBanMgr) UnbanNickname(nickname string) error {
+	args := m.Called(nickname)
+	return args.Error(0)
+}
+
+func (m *MockBanMgr) IsNicknameBanned(nickname string) bool {
+	args := m.Called(nickname)
+	return args.Bool(0)
+}
+
+func (m *MockBanMgr) ListBannedIPs() ([]string, error) {
+	args := m.Called()
+	return args.Get(0).([]string), args.Error(1)
+}
+
+func (m *MockBanMgr) ListBannedUsernames() ([]string, error) {
+	args := m.Called()
+	return args.Get(0).([]string), args.Error(1)
+}
+
+func (m *MockBanMgr) ListBannedNicknames() ([]string, error) {
+	args := m.Called()
+	return args.Get(0).([]string), args.Error(1)
+}