add test for recursive depth

x/evm/contracts/counter/Counter.sol

@@ -3,6 +3,7 @@ pragma solidity ^0.8.24;
 
 import "../i_ibc_async_callback/IIBCAsyncCallback.sol";
 import "../i_cosmos/ICosmos.sol";
+import "../strings/Strings.sol";
 
 contract Counter is IIBCAsyncCallback {
     uint256 public count;
@@ -39,4 +40,36 @@ contract Counter is IIBCAsyncCallback {
     function get_blockhash(uint64 n) external view returns (bytes32) {
         return blockhash(n);
     }
+
+    function recursive(uint64 n) public {
+        if (n == 0) {
+            return;
+        }
+
+        COSMOS_CONTRACT.execute_cosmos(_recursive(n));
+
+        // to test branching
+        COSMOS_CONTRACT.execute_cosmos(_recursive(n));
+    }
+
+    function _recursive(uint64 n) internal returns (string memory message) {
+        message = string(
+            abi.encodePacked(
+                '{"@type": "/minievm.evm.v1.MsgCall",',
+                '"sender": "',
+                COSMOS_CONTRACT.to_cosmos_address(address(this)),
+                '",',
+                '"contract_addr": "',
+                Strings.toHexString(address(this)),
+                '",',
+                '"input": "',
+                Strings.toHexString(
+                    abi.encodePacked(this.recursive.selector, abi.encode(n - 1))
+                ),
+                '",',
+                '"value": "0",',
+                '"access_list": []}'
+            )
+        );
+    }
 }

x/evm/contracts/erc20_wrapper/ERC20Wrapper.sol

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 pragma solidity ^0.8.24;
 
-import "../util/Strings.sol";
+import "../strings/Strings.sol";
 import "../i_cosmos/ICosmos.sol";
 import "../erc20_factory/ERC20Factory.sol";
 import "../i_erc20/IERC20.sol";

x/evm/contracts/util/Strings.sol → x/evm/contracts/strings/Strings.sol

@@ -10,6 +10,7 @@ library Strings {
      */
     error StringsInsufficientHexLength(uint256 value, uint256 length);
 
+    // uint256 to hex string
     function toHexString(
         uint256 value,
         uint256 length
@@ -28,6 +29,19 @@ library Strings {
         return string(buffer);
     }
 
+    // bytes to hex string
+    function toHexString(bytes memory buffer) internal pure returns (string memory) {
+        bytes memory converted = new bytes(buffer.length * 2);
+        bytes memory _base = "0123456789abcdef";
+
+        for (uint256 i = 0; i < buffer.length; i++) {
+            converted[i * 2] = _base[uint8(buffer[i]) / _base.length];
+            converted[i * 2 + 1] = _base[uint8(buffer[i]) % _base.length];
+        }
+
+        return string(abi.encodePacked("0x", converted));
+    }
+
     function toHexString(address addr) internal pure returns (string memory) {
         return toHexString(uint256(uint160(addr)), ADDRESS_LENGTH);
     }