test: increase total coverage from 40.7% to 46.1%

Add comprehensive mhfpacket Parse/Build/Opcode tests covering nearly
all packet types (78.3% -> 95.7%). Add channelserver tests for
BackportQuest and GuildIcon Scan/Value round-trips.

server/channelserver/handlers_quest_backport_test.go

@@ -0,0 +1,128 @@
+package channelserver
+
+import (
+	"encoding/binary"
+	"testing"
+
+	_config "erupe-ce/config"
+)
+
+func TestBackportQuest_Basic(t *testing.T) {
+	// Set up config for the test
+	oldConfig := _config.ErupeConfig
+	defer func() { _config.ErupeConfig = oldConfig }()
+
+	_config.ErupeConfig = &_config.Config{}
+	_config.ErupeConfig.RealClientMode = _config.ZZ
+
+	// Create a quest data buffer large enough for BackportQuest to work with.
+	// The function reads a uint32 from data[0:4] as offset, then works at offset+96.
+	// We need at least offset + 96 + 108 + 6*8 bytes.
+	// Set offset (wp base) = 0, so wp starts at 96, rp at 100.
+	data := make([]byte, 512)
+	binary.LittleEndian.PutUint32(data[0:4], 0) // offset = 0
+
+	// Fill some data at the rp positions so we can verify copies
+	for i := 100; i < 400; i++ {
+		data[i] = byte(i & 0xFF)
+	}
+
+	result := BackportQuest(data)
+	if result == nil {
+		t.Fatal("BackportQuest returned nil")
+	}
+	if len(result) != len(data) {
+		t.Errorf("BackportQuest changed data length: got %d, want %d", len(result), len(data))
+	}
+}
+
+func TestBackportQuest_S6Mode(t *testing.T) {
+	oldConfig := _config.ErupeConfig
+	defer func() { _config.ErupeConfig = oldConfig }()
+
+	_config.ErupeConfig = &_config.Config{}
+	_config.ErupeConfig.RealClientMode = _config.S6
+
+	data := make([]byte, 512)
+	binary.LittleEndian.PutUint32(data[0:4], 0)
+
+	for i := 0; i < len(data); i++ {
+		data[i+4] = byte(i % 256)
+		if i+4 >= len(data)-1 {
+			break
+		}
+	}
+
+	// Set some values at data[8:12] so we can check they get copied to data[16:20]
+	binary.LittleEndian.PutUint32(data[8:12], 0xDEADBEEF)
+
+	result := BackportQuest(data)
+	if result == nil {
+		t.Fatal("BackportQuest returned nil")
+	}
+
+	// In S6 mode, data[16:20] should be copied from data[8:12]
+	got := binary.LittleEndian.Uint32(result[16:20])
+	if got != 0xDEADBEEF {
+		t.Errorf("S6 mode: data[16:20] = 0x%X, want 0xDEADBEEF", got)
+	}
+}
+
+func TestBackportQuest_G91Mode_PatternReplacement(t *testing.T) {
+	oldConfig := _config.ErupeConfig
+	defer func() { _config.ErupeConfig = oldConfig }()
+
+	_config.ErupeConfig = &_config.Config{}
+	_config.ErupeConfig.RealClientMode = _config.G91
+
+	data := make([]byte, 512)
+	binary.LittleEndian.PutUint32(data[0:4], 0)
+
+	// Insert an armor sphere pattern at a known location
+	// Pattern: 0x0A, 0x00, 0x01, 0x33 -> should replace bytes at +2 with 0xD7, 0x00
+	offset := 300
+	data[offset] = 0x0A
+	data[offset+1] = 0x00
+	data[offset+2] = 0x01
+	data[offset+3] = 0x33
+
+	result := BackportQuest(data)
+
+	// After BackportQuest, the pattern's last 2 bytes should be replaced
+	if result[offset+2] != 0xD7 || result[offset+3] != 0x00 {
+		t.Errorf("G91 pattern replacement failed: got [0x%X, 0x%X], want [0xD7, 0x00]",
+			result[offset+2], result[offset+3])
+	}
+}
+
+func TestBackportQuest_F5Mode(t *testing.T) {
+	oldConfig := _config.ErupeConfig
+	defer func() { _config.ErupeConfig = oldConfig }()
+
+	_config.ErupeConfig = &_config.Config{}
+	_config.ErupeConfig.RealClientMode = _config.F5
+
+	data := make([]byte, 512)
+	binary.LittleEndian.PutUint32(data[0:4], 0)
+
+	result := BackportQuest(data)
+	if result == nil {
+		t.Fatal("BackportQuest returned nil")
+	}
+}
+
+func TestBackportQuest_G101Mode(t *testing.T) {
+	oldConfig := _config.ErupeConfig
+	defer func() { _config.ErupeConfig = oldConfig }()
+
+	_config.ErupeConfig = &_config.Config{}
+	_config.ErupeConfig.RealClientMode = _config.G101
+
+	data := make([]byte, 512)
+	binary.LittleEndian.PutUint32(data[0:4], 0)
+
+	result := BackportQuest(data)
+	if result == nil {
+		t.Fatal("BackportQuest returned nil")
+	}
+}