diff --git a/src/util/hex.cc b/src/util/hex.cc
index 9f87cd3b..729c3551 100644
--- a/src/util/hex.cc
+++ b/src/util/hex.cc
@@ -4,25 +4,22 @@
 
 #include "absl/strings/str_cat.h"
 #include "absl/strings/str_format.h"
-#include "absl/strings/str_join.h"
 
 namespace yaze {
 namespace util {
 
 namespace {
 
-void HandleHexStringParams(const std::string &hex,
-                           const HexStringParams &params) {
-  std::string result = hex;
+void HandleHexStringParams(std::string &hex, const HexStringParams &params) {
   switch (params.prefix) {
     case HexStringParams::Prefix::kDollar:
-      result = absl::StrCat("$", result);
+      hex = absl::StrCat("$", hex);
       break;
     case HexStringParams::Prefix::kHash:
-      result = absl::StrCat("#", result);
+      hex = absl::StrCat("#", hex);
       break;
     case HexStringParams::Prefix::k0x:
-      result = absl::StrCat("0x", result);
+      hex = absl::StrCat("0x", hex);
     case HexStringParams::Prefix::kNone:
     default:
       break;
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 6c3568da..218d083e 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -17,6 +17,7 @@ add_executable(
   yaze_test.cc
   rom_test.cc
   test_editor.cc
+  hex_test.cc
   gfx/compression_test.cc
   gfx/snes_palette_test.cc
   zelda3/message_test.cc
diff --git a/test/hex_test.cc b/test/hex_test.cc
new file mode 100644
index 00000000..d3febbe1
--- /dev/null
+++ b/test/hex_test.cc
@@ -0,0 +1,103 @@
+#include "testing.h"
+
+#include "util/hex.h"
+
+namespace yaze {
+namespace test {
+
+using ::testing::Eq;
+
+TEST(HexTest, HexByte) {
+  // Test basic byte conversion
+  EXPECT_THAT(util::HexByte(0x00), Eq("$00"));
+  EXPECT_THAT(util::HexByte(0xFF), Eq("$FF"));
+  EXPECT_THAT(util::HexByte(0x1A), Eq("$1A"));
+
+  // Test different prefixes
+  util::HexStringParams params;
+  params.prefix = util::HexStringParams::Prefix::kNone;
+  EXPECT_THAT(util::HexByte(0x1A, params), Eq("1A"));
+
+  params.prefix = util::HexStringParams::Prefix::kHash;
+  EXPECT_THAT(util::HexByte(0x1A, params), Eq("#1A"));
+
+  params.prefix = util::HexStringParams::Prefix::k0x;
+  EXPECT_THAT(util::HexByte(0x1A, params), Eq("0x1A"));
+
+  // Test lowercase
+  params.prefix = util::HexStringParams::Prefix::kNone;
+  params.uppercase = false;
+  EXPECT_THAT(util::HexByte(0x1A, params), Eq("1a"));
+}
+
+TEST(HexTest, HexWord) {
+  // Test basic word conversion
+  EXPECT_THAT(util::HexWord(0x0000), Eq("$0000"));
+  EXPECT_THAT(util::HexWord(0xFFFF), Eq("$FFFF"));
+  EXPECT_THAT(util::HexWord(0x1A2B), Eq("$1A2B"));
+
+  // Test different prefixes
+  util::HexStringParams params;
+  params.prefix = util::HexStringParams::Prefix::kNone;
+  EXPECT_THAT(util::HexWord(0x1A2B, params), Eq("1A2B"));
+
+  params.prefix = util::HexStringParams::Prefix::kHash;
+  EXPECT_THAT(util::HexWord(0x1A2B, params), Eq("#1A2B"));
+
+  params.prefix = util::HexStringParams::Prefix::k0x;
+  EXPECT_THAT(util::HexWord(0x1A2B, params), Eq("0x1A2B"));
+
+  // Test lowercase
+  params.prefix = util::HexStringParams::Prefix::kNone;
+  params.uppercase = false;
+  EXPECT_THAT(util::HexWord(0x1A2B, params), Eq("1a2b"));
+}
+
+TEST(HexTest, HexLong) {
+  // Test basic long conversion
+  EXPECT_THAT(util::HexLong(0x000000), Eq("$000000"));
+  EXPECT_THAT(util::HexLong(0xFFFFFF), Eq("$FFFFFF"));
+  EXPECT_THAT(util::HexLong(0x1A2B3C), Eq("$1A2B3C"));
+
+  // Test different prefixes
+  util::HexStringParams params;
+  params.prefix = util::HexStringParams::Prefix::kNone;
+  EXPECT_THAT(util::HexLong(0x1A2B3C, params), Eq("1A2B3C"));
+
+  params.prefix = util::HexStringParams::Prefix::kHash;
+  EXPECT_THAT(util::HexLong(0x1A2B3C, params), Eq("#1A2B3C"));
+
+  params.prefix = util::HexStringParams::Prefix::k0x;
+  EXPECT_THAT(util::HexLong(0x1A2B3C, params), Eq("0x1A2B3C"));
+
+  // Test lowercase
+  params.prefix = util::HexStringParams::Prefix::kNone;
+  params.uppercase = false;
+  EXPECT_THAT(util::HexLong(0x1A2B3C, params), Eq("1a2b3c"));
+}
+
+TEST(HexTest, HexLongLong) {
+  // Test basic long long conversion
+  EXPECT_THAT(util::HexLongLong(0x00000000), Eq("$00000000"));
+  EXPECT_THAT(util::HexLongLong(0xFFFFFFFF), Eq("$FFFFFFFF"));
+  EXPECT_THAT(util::HexLongLong(0x1A2B3C4D), Eq("$1A2B3C4D"));
+
+  // Test different prefixes
+  util::HexStringParams params;
+  params.prefix = util::HexStringParams::Prefix::kNone;
+  EXPECT_THAT(util::HexLongLong(0x1A2B3C4D, params), Eq("1A2B3C4D"));
+
+  params.prefix = util::HexStringParams::Prefix::kHash;
+  EXPECT_THAT(util::HexLongLong(0x1A2B3C4D, params), Eq("#1A2B3C4D"));
+
+  params.prefix = util::HexStringParams::Prefix::k0x;
+  EXPECT_THAT(util::HexLongLong(0x1A2B3C4D, params), Eq("0x1A2B3C4D"));
+
+  // Test lowercase
+  params.prefix = util::HexStringParams::Prefix::kNone;
+  params.uppercase = false;
+  EXPECT_THAT(util::HexLongLong(0x1A2B3C4D, params), Eq("1a2b3c4d"));
+}
+
+}  // namespace test
+}  // namespace yaze 
\ No newline at end of file