diff --git a/src/klotski_core/common_code/serialize.cc b/src/klotski_core/common_code/serialize.cc
index e6a4097..81bf169 100644
--- a/src/klotski_core/common_code/serialize.cc
+++ b/src/klotski_core/common_code/serialize.cc
@@ -46,9 +46,9 @@ CommonCode::CommonCode(const std::string &common_code) { // convert from 1 ~ 9 b
         result <<= 4;
         if (bit >= '0' && bit <= '9') { // 0 ~ 9
             result |= (bit - 48);
-        } else if (bit >= 'A' && bit <= 'Z') { // A ~ Z
+        } else if (bit >= 'A' && bit <= 'F') { // A ~ F
             result |= (bit - 55);
-        } else if (bit >= 'a' && bit <= 'z') { // a ~ z
+        } else if (bit >= 'a' && bit <= 'f') { // a ~ f
             result |= (bit - 87);
         } else {
             throw CommonCodeException("common code with invalid character"); // unknown character
diff --git a/src/klotski_core/short_code/serialize.cc b/src/klotski_core/short_code/serialize.cc
index fa9d44c..26e107d 100644
--- a/src/klotski_core/short_code/serialize.cc
+++ b/src/klotski_core/short_code/serialize.cc
@@ -29,11 +29,12 @@ ShortCode::ShortCode(const std::string &short_code) { // 5-bits string decode
         if (bit >= 'a' && bit <= 'z') {
             bit -= 32; // convert to uppercase
         }
-        if (bit >= '1' && bit <= 'Z') { // valid characters
-            result += (bit = SHORT_CODE_TABLE_REV[bit - 49]); // table convert
-            if (bit == -1) {
-                throw ShortCodeException("short code with invalid character"); // unknown character
-            }
+        if (bit < '1' || bit > 'Z') { // invalid characters
+            throw ShortCodeException("short code with invalid character");
+        }
+        result += (bit = SHORT_CODE_TABLE_REV[bit - 49]); // table convert
+        if (bit == -1) { // invalid character
+            throw ShortCodeException("short code with invalid character");
         }
     }
     if (!ShortCode::check(result)) { // check converted short code
diff --git a/test/basic/all_cases.cc b/test/basic/all_cases.cc
index b936526..952d55d 100644
--- a/test/basic/all_cases.cc
+++ b/test/basic/all_cases.cc
@@ -23,6 +23,7 @@ TEST(AllCases, basic_ranges_mutex) {
     for (auto &t : threads) {
         t = std::thread(BasicRanges::build);
     }
+    usleep(1000); // wait 1ms -> avoid mutex unlocked
     EXPECT_EQ(BasicRanges::status(), BasicRanges::BUILDING);
     for (auto &t : threads) {
         t.join();
@@ -55,6 +56,7 @@ TEST(AllCases, all_cases_mutex) {
     for (auto &t : threads) {
         t = std::thread(AllCases::build);
     }
+    usleep(1000); // wait 1ms -> avoid mutex unlocked
     EXPECT_EQ(AllCases::status(), AllCases::BUILDING);
     for (auto &t : threads) {
         t.join();
diff --git a/test/codec/common_code.cc b/test/codec/common_code.cc
index 9f781c6..506bdbb 100644
--- a/test/codec/common_code.cc
+++ b/test/codec/common_code.cc
@@ -11,9 +11,26 @@ using klotski::CommonCode;
 
 const static uint64_t TEST_CODE = 0x1'A9BF'0C00;
 const static std::string TEST_CODE_STR = "1A9BF0C00";
-const static uint64_t TEST_ERR_CODE = 0x1'2190'2300;
 
-// TODO: test some invalid cases
+inline void SHOULD_PANIC(const std::function<void(void)> &func) {
+    bool panic_flag = false;
+    try {
+        func();
+    } catch (klotski::CommonCodeException&) {
+        panic_flag = true;
+    }
+    EXPECT_EQ(panic_flag, true);
+}
+
+TEST(CommonCode, invalid) {
+    EXPECT_NE(CommonCode::check(0x3'A9'BF'0C'00), true); // invalid 2x2 block
+    EXPECT_NE(CommonCode::check(0x1'D9'BF'0C'00), true); // invalid block range
+    EXPECT_NE(CommonCode::check(0x1'A9'BF'FC'00), true); // less than 2 space
+    EXPECT_NE(CommonCode::check(0x1'A0'BF'0C'01), true); // low bits not fill zero
+
+    SHOULD_PANIC([](){ CommonCode::from_string("0123456789"); }); // length > 9
+    SHOULD_PANIC([](){ CommonCode::from_string("123J432A9"); }); // with invalid `J`
+}
 
 TEST(CommonCode, code_verify) {
     std::thread threads[16];
diff --git a/test/codec/raw_code.cc b/test/codec/raw_code.cc
index d8b212d..228ba50 100644
--- a/test/codec/raw_code.cc
+++ b/test/codec/raw_code.cc
@@ -8,9 +8,11 @@ using klotski::AllCases;
 using klotski::CommonCode;
 
 const static uint64_t TEST_CODE = 0x0603'EDF5'CAFF'F5E2;
-const static uint64_t TEST_ERR_CODE = 0x0A34'182B'3810'2D21;
 
-// TODO: test some invalid cases
+TEST(RawCode, invalid) {
+    EXPECT_NE(RawCode::check(0x0A34'182B'3810'2D21), true); // invalid code
+    EXPECT_NE(RawCode::check(0x8603'EDF5'CAFF'F5E2), true); // high 4-bits not zero
+}
 
 TEST(RawCode, code_verify) {
     std::thread threads[16];
diff --git a/test/codec/short_code.cc b/test/codec/short_code.cc
index 3f9bc46..59d7f2b 100644
--- a/test/codec/short_code.cc
+++ b/test/codec/short_code.cc
@@ -23,14 +23,11 @@ inline void SHOULD_PANIC(const std::function<void(void)> &func) {
 }
 
 TEST(ShortCode, invalid) {
-    EXPECT_NE(ShortCode::check(29670987), true);
-
-    std::cout << ShortCode::from_string("R50EH") << std::endl;
-
+    EXPECT_NE(ShortCode::check(-1), true); // out of short code range
+    EXPECT_NE(ShortCode::check(29670987), true); // out of short code range
     SHOULD_PANIC([](){ ShortCode::from_string("R50EH"); }); // with invalid `0`
-//    SHOULD_PANIC([](){ ShortCode::from_string("123456"); }); // length != 5
-//    SHOULD_PANIC([](){ ShortCode::from_string("Z9EFV"); }); // out of short code range
-
+    SHOULD_PANIC([](){ ShortCode::from_string("123456"); }); // length != 5
+    SHOULD_PANIC([](){ ShortCode::from_string("Z9EFV"); }); // out of short code range
 }
 
 TEST(ShortCode, speed_up) {
@@ -41,6 +38,7 @@ TEST(ShortCode, speed_up) {
     for (auto &t : threads) {
         t = std::thread(ShortCode::speed_up, ShortCode::NORMAL);
     }
+    usleep(1000); // wait 1ms -> avoid mutex unlocked
     EXPECT_EQ(BasicRanges::status(), BasicRanges::BUILDING);
     for (auto &t : threads) {
         t.join();