diff --git a/src/core_test/CMakeLists.txt b/src/core_test/CMakeLists.txt
index 082ec53..69474d6 100644
--- a/src/core_test/CMakeLists.txt
+++ b/src/core_test/CMakeLists.txt
@@ -17,6 +17,7 @@ add_library(test_helper
     helper/internal/parallel.cc
     helper/internal/hash.cc
     helper/internal/group.cc
+    helper/internal/mirror.cc
 )
 target_link_libraries(test_helper PRIVATE klotski_core bs::thread_pool md5sum::md5 xxHash::xxh3)
 
diff --git a/src/core_test/codec/common_code.cc b/src/core_test/codec/common_code.cc
index 2a86771..6f5e300 100644
--- a/src/core_test/codec/common_code.cc
+++ b/src/core_test/codec/common_code.cc
@@ -3,6 +3,7 @@
 
 #include "test_samples.h"
 #include "helper/expect.h"
+#include "helper/mirror.h"
 #include "helper/parallel.h"
 
 #include "raw_code/raw_code.h"
@@ -163,18 +164,23 @@ TEST(CommonCode, code_verify) {
 TEST(CommonCode, code_mirror) {
     COMMON_CODE_PARALLEL({
         const auto mirror_v = code.to_vertical_mirror();
-        EXPECT_TRUE(CommonCode::check(mirror_v.unwrap()));
+        EXPECT_EQ(mirror_v, helper::get_vertical_mirror(code));
         EXPECT_EQ(mirror_v.to_vertical_mirror(), code);
-        EXPECT_FALSE(mirror_v.is_vertical_mirror()); // not exist
-        EXPECT_NE(mirror_v, code);
+        if (mirror_v == code) {
+            EXPECT_TRUE(code.is_vertical_mirror());
+        } else {
+            EXPECT_FALSE(code.is_vertical_mirror());
+        }
+    });
 
+    COMMON_CODE_PARALLEL({
         const auto mirror_h = code.to_horizontal_mirror();
-        EXPECT_TRUE(CommonCode::check(mirror_h.unwrap()));
+        EXPECT_EQ(mirror_h, helper::get_horizontal_mirror(code));
         EXPECT_EQ(mirror_h.to_horizontal_mirror(), code);
-        if (mirror_h.is_horizontal_mirror()) {
-            EXPECT_EQ(mirror_h, code);
+        if (mirror_h == code) {
+            EXPECT_TRUE(code.is_horizontal_mirror());
         } else {
-            EXPECT_NE(mirror_h, code);
+            EXPECT_FALSE(code.is_horizontal_mirror());
         }
     });
 }
diff --git a/src/core_test/codec/raw_code.cc b/src/core_test/codec/raw_code.cc
index de38adc..f01a598 100644
--- a/src/core_test/codec/raw_code.cc
+++ b/src/core_test/codec/raw_code.cc
@@ -2,6 +2,7 @@
 
 #include "test_samples.h"
 #include "helper/expect.h"
+#include "helper/mirror.h"
 #include "helper/parallel.h"
 
 #include "utils/common.h"
@@ -131,18 +132,23 @@ TEST(RawCode, code_verify) {
 TEST(RawCode, code_mirror) {
     RAW_CODE_PARALLEL({
         const auto mirror_v = code.to_vertical_mirror();
-        EXPECT_TRUE(RawCode::check(mirror_v.unwrap()));
+        EXPECT_EQ(mirror_v, helper::get_vertical_mirror(code));
         EXPECT_EQ(mirror_v.to_vertical_mirror(), code);
-        EXPECT_FALSE(mirror_v.is_vertical_mirror()); // not exist
-        EXPECT_NE(mirror_v, code);
+        if (mirror_v == code) {
+            EXPECT_TRUE(code.is_vertical_mirror());
+        } else {
+            EXPECT_FALSE(code.is_vertical_mirror());
+        }
+    });
 
+    RAW_CODE_PARALLEL({
         const auto mirror_h = code.to_horizontal_mirror();
-        EXPECT_TRUE(RawCode::check(mirror_h.unwrap()));
+        EXPECT_EQ(mirror_h, helper::get_horizontal_mirror(code));
         EXPECT_EQ(mirror_h.to_horizontal_mirror(), code);
-        if (mirror_h.is_horizontal_mirror()) {
-            EXPECT_EQ(mirror_h, code);
+        if (mirror_h == code) {
+            EXPECT_TRUE(code.is_horizontal_mirror());
         } else {
-            EXPECT_NE(mirror_h, code);
+            EXPECT_FALSE(code.is_horizontal_mirror());
         }
     });
 }
diff --git a/src/core_test/helper/internal/mirror.cc b/src/core_test/helper/internal/mirror.cc
new file mode 100644
index 0000000..7854cc3
--- /dev/null
+++ b/src/core_test/helper/internal/mirror.cc
@@ -0,0 +1,88 @@
+#include "helper/mirror.h"
+
+#include "utils/common.h"
+
+using klotski::codec::RawCode;
+using klotski::codec::CommonCode;
+
+using namespace klotski;
+
+RawCode helper::get_horizontal_mirror(RawCode code) {
+    uint64_t new_code = 0;
+
+    for (int addr = 0; addr < 20; ++addr) {
+
+        auto block = (code.unwrap() >> (addr * 3)) & 0b111;
+
+        if (block == BLOCK_CE_1x1) {
+            auto target_addr = addr - (addr % 4);
+            target_addr += 3 - (addr % 4);
+            new_code |= K_MASK_1x1 << (target_addr * 3);
+        } else if (block == BLOCK_CE_2x1) {
+            auto target_addr = addr - (addr % 4);
+            target_addr += 3 - (addr % 4);
+            new_code |= K_MASK_2x1 << (target_addr * 3);
+        } else if (block == BLOCK_CE_1x2) {
+            auto target_addr = addr - (addr % 4);
+            if (addr % 4 == 0) {
+                target_addr += 2;
+            } else if (addr % 4 == 1) {
+                target_addr += 1;
+            }
+            new_code |= K_MASK_1x2 << (target_addr * 3);
+        } else if (block == BLOCK_CE_2x2) {
+            auto target_addr = addr - (addr % 4);
+            if (addr % 4 == 0) {
+                target_addr += 2;
+            } else if (addr % 4 == 1) {
+                target_addr += 1;
+            }
+            new_code |= K_MASK_2x2 << (target_addr * 3);
+        }
+
+    }
+
+    return RawCode::unsafe_create(new_code);
+}
+
+RawCode helper::get_vertical_mirror(RawCode code) {
+    uint64_t new_code = 0;
+
+    for (int addr = 0; addr < 20; ++addr) {
+
+        auto block = (code.unwrap() >> (addr * 3)) & 0b111;
+
+        if (block == BLOCK_CE_1x1) {
+            auto target_addr = addr - (addr % 4);
+            target_addr = 16 - target_addr;
+            target_addr += (addr % 4);
+            new_code |= K_MASK_1x1 << (target_addr * 3);
+        } else if (block == BLOCK_CE_2x1) {
+            auto target_addr = addr - (addr % 4);
+            target_addr = 12 - target_addr;
+            target_addr += (addr % 4);
+            new_code |= K_MASK_2x1 << (target_addr * 3);
+        } else if (block == BLOCK_CE_1x2) {
+            auto target_addr = addr - (addr % 4);
+            target_addr = 16 - target_addr;
+            target_addr += (addr % 4);
+            new_code |= K_MASK_1x2 << (target_addr * 3);
+        } else if (block == BLOCK_CE_2x2) {
+            auto target_addr = addr - (addr % 4);
+            target_addr = 12 - target_addr;
+            target_addr += (addr % 4);
+            new_code |= K_MASK_2x2 << (target_addr * 3);
+        }
+
+    }
+
+    return RawCode::unsafe_create(new_code);
+}
+
+CommonCode helper::get_vertical_mirror(CommonCode code) {
+    return get_vertical_mirror(code.to_raw_code()).to_common_code();
+}
+
+CommonCode helper::get_horizontal_mirror(CommonCode code) {
+    return get_horizontal_mirror(code.to_raw_code()).to_common_code();
+}
diff --git a/src/core_test/helper/mirror.h b/src/core_test/helper/mirror.h
index 691943b..7bc94f6 100644
--- a/src/core_test/helper/mirror.h
+++ b/src/core_test/helper/mirror.h
@@ -1,3 +1,18 @@
 #pragma once
 
-// TODO: mirror convert of RawCode
+#include "raw_code/raw_code.h"
+
+namespace helper {
+
+using klotski::codec::RawCode;
+using klotski::codec::CommonCode;
+
+RawCode get_vertical_mirror(RawCode code);
+
+RawCode get_horizontal_mirror(RawCode code);
+
+CommonCode get_vertical_mirror(CommonCode code);
+
+CommonCode get_horizontal_mirror(CommonCode code);
+
+} // namespace helper