add test suite for sell and buy erc20

.github/workflows/test.yml

@@ -1,45 +0,0 @@
-name: CI
-
-on:
-  push:
-  pull_request:
-  workflow_dispatch:
-
-env:
-  FOUNDRY_PROFILE: ci
-
-jobs:
-  check:
-    strategy:
-      fail-fast: true
-
-    name: Foundry project
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          submodules: recursive
-
-      - name: Install Foundry
-        uses: foundry-rs/foundry-toolchain@v1
-        with:
-          version: nightly
-
-      - name: Show Forge version
-        run: |
-          forge --version
-
-      - name: Run Forge fmt
-        run: |
-          forge fmt --check
-        id: fmt
-
-      - name: Run Forge build
-        run: |
-          forge build --sizes
-        id: build
-
-      - name: Run Forge tests
-        run: |
-          forge test -vvv
-        id: test

.gitignore

@@ -12,3 +12,6 @@ docs/
 
 # Dotenv file
 .env
+
+# Vim buffer file
+*.swp

.gitmodules

@@ -3,7 +3,7 @@
 	url = https://github.com/foundry-rs/forge-std
 [submodule "lib/openzeppelin-contracts"]
 	path = lib/openzeppelin-contracts
-	url = https://github.com/openzeppelin/openzeppelin-contracts
+	url = https://github.com/OpenZeppelin/openzeppelin-contracts
 [submodule "lib/foundry-devops"]
 	path = lib/foundry-devops
 	url = https://github.com/Cyfrin/foundry-devops

lib/forge-std

@@ -0,0 +1 @@
+Subproject commit b93cf4bc34ff214c099dc970b153f85ade8c9f66

lib/foundry-devops

@@ -0,0 +1 @@
+Subproject commit 90b6dde61322b916020d396817023602f4ef96ed

lib/openzeppelin-contracts

@@ -0,0 +1 @@
+Subproject commit acd4ff74de833399287ed6b31b4debf6b2b35527

src/TokenDivider.sol

@@ -1,327 +1,344 @@
-// SPDX-License-Identifier: MIT
-pragma solidity ^0.8.18;
-
-import {IERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
-import {ERC20ToGenerateNftFraccion} from "src/token/ERC20ToGenerateNftFraccion.sol";
-import {IERC721, ERC721} from "@openzeppelin/contracts/token/ERC721/ERC721.sol";
-import {IERC721Receiver} from "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
-import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
-
-/**
- * @title TokenDivider
- * @author Juan Pedro Ventura Baltian, 14 years old
- * @notice This contracts was created, with the intention to make a new market of nft franctions 
- * There are a function to divide an nft, then you can sell and buy some fraction of nft, that are basicaly 
- * erc20 tokens, each nft pegged to an nft.There are some validations, to make the platforme the most secure 
- * as possible.This is the first project that i code alone, in blockchain, foundry and solidity. 
- * Thank you so much for read it.
- */
- 
-
-contract  TokenDivider is IERC721Receiver,Ownable   {
-
-    error TokenDivider__NotFromNftOwner();
-    error  TokenDivider__NotEnoughErc20Balance();
-    error TokenDivider__NftTransferFailed();
-    error TokenDivider__InsuficientBalance();
-    error TokenDivider__CantTransferToAddressZero();
-    error TokenDivider__TransferFailed();
-    error TokenDivider__NftAddressIsZero();
-    error TokenDivider__AmountCantBeZero();
-    error TokenDivider__InvalidSeller();
-    error TokenDivier__InvalidAmount();
-    error TokenDivider__IncorrectEtherAmount();
-    error TokenDivider__InsuficientEtherForFees();
-
-    struct ERC20Info {
-        address erc20Address;
-        uint256 tokenId;
-    }
-
-    struct SellOrder {
-        address seller;
-        address erc20Address;
-        uint256 price;
-        uint256 amount;
-    }
-
-
-    /**
-     * @dev balances Relates a user with an amount of a erc20 token, this erc20 tokens is an nft fraction
-     
-     @dev nftToErc20Info Relates an nft with the erc20 pegged, and othe data like the erc20 amount, or the tokenId
-     
-     @dev s_userToSellOrders Relates a user with an array of sell orders, that each sell order 
-     has a seller, an erc20 that is the token to sell, a price and an amount of erc20 to sell
-     
-     */
-    mapping(address user => mapping(address erc20Address => uint256 amount)) balances; 
-    mapping(address nft => ERC20Info) nftToErc20Info;
-    mapping(address user => SellOrder[] orders) s_userToSellOrders;
-    mapping(address erc20 =>  address nft) erc20ToNft;
-    mapping(address erc20 => uint256 totalErc20Minted) erc20ToMintedAmount;
-
-    event NftDivided(address indexed nftAddress, uint256 indexed amountErc20Minted, address indexed erc20Minted);
-    event NftClaimed(address indexed nftAddress);
-    event TokensTransfered(uint256 indexed amount, address indexed erc20Address);
-    event OrderPublished(uint256 indexed amount, address indexed seller, address indexed nftPegged);
-    event OrderSelled(address indexed buyer, uint256 price);
-
-
-    /**
-     * 
-     *  Only the owner of the nft can call a function with this modifier
-     */
-    modifier onlyNftOwner(address nft, uint256 tokenId) {
-        if(msg.sender != IERC721(nft).ownerOf(tokenId)) {
-            revert TokenDivider__NotFromNftOwner();
-        }
-        _;
-    }
-
-    constructor() Ownable(msg.sender) {}
-
-
-
-    /**
-     * @dev Handles the receipt of an ERC721 token. This function is called whenever an ERC721 token is transferred to this contract.
-     */
-    function onERC721Received(
-        address /* operator */,
-        address /* from */,
-        uint256 /*  tokenId */,
-        bytes calldata /* data */
-    ) external pure override returns (bytes4) {
-        // Return this value to confirm the receipt of the NFT
-        return this.onERC721Received.selector;
-    }
-
-    /**
-     * 
-     * @param nftAddress The addres of the nft to divide
-     * @param tokenId The id of the token to divide
-     * @param amount The amount of erc20 tokens to mint for the nft
-     * 
-     * @dev in this function, the nft passed as parameter, is locked by transfering it to this contract, then, it gives to the 
-     * person calling this function an amount of erc20, beeing like a fraction of this nft.
-     */
-
-    function divideNft(address nftAddress, uint256 tokenId, uint256 amount) onlyNftOwner(nftAddress, tokenId) onlyNftOwner(nftAddress ,tokenId) external {
-        
-
-        if(nftAddress == address(0)) { revert TokenDivider__NftAddressIsZero(); }
-        if(amount == 0) { revert TokenDivider__AmountCantBeZero(); }
-
-        ERC20ToGenerateNftFraccion erc20Contract = new ERC20ToGenerateNftFraccion(
-            string(abi.encodePacked(ERC721(nftAddress).name(), "Fraccion")), 
-            string(abi.encodePacked("F", ERC721(nftAddress).symbol())));
-
-        erc20Contract.mint(address(this), amount);
-        address erc20 = address(erc20Contract);
-
-        IERC721(nftAddress).safeTransferFrom(msg.sender, address(this), tokenId, "");
-
-        if(IERC721(nftAddress).ownerOf(tokenId) == msg.sender) { revert TokenDivider__NftTransferFailed(); }
-
-        balances[msg.sender][erc20] = amount;
-        nftToErc20Info[nftAddress] = ERC20Info({erc20Address: erc20, tokenId: tokenId});
-        erc20ToMintedAmount[erc20] = amount;
-        erc20ToNft[erc20] = nftAddress;
-
-        emit NftDivided(nftAddress, amount, erc20);
-        
-        bool transferSuccess = IERC20(erc20).transfer(msg.sender, amount);
-        if(!transferSuccess) {
-            revert TokenDivider__TransferFailed();
-        }
-    }
-
-    /**
-     * 
-     * @param nftAddress  The address of the nft to claim
-     * 
-     * @dev in this function, if you have all the erc20 minted for the nft, you can call this function to claim the nft, 
-     * giving to the contract all the erc20 and it will give you back the nft
-     */
-
-    function claimNft(address nftAddress) external {
-
-        if(nftAddress == address(0)) {
-            revert TokenDivider__NftAddressIsZero();
-        }
-
-        ERC20Info storage tokenInfo = nftToErc20Info[nftAddress];
-
-        if(balances[msg.sender][tokenInfo.erc20Address] < erc20ToMintedAmount[tokenInfo.erc20Address]) {
-            revert TokenDivider__NotEnoughErc20Balance();
-        }
-
-        ERC20ToGenerateNftFraccion(tokenInfo.erc20Address).burnFrom(msg.sender, erc20ToMintedAmount[tokenInfo.erc20Address]);
-
-        balances[msg.sender][tokenInfo.erc20Address] = 0;
-        erc20ToMintedAmount[tokenInfo.erc20Address] = 0;
-
-        emit NftClaimed(nftAddress);
-    
-        IERC721(nftAddress).safeTransferFrom(address(this), msg.sender, tokenInfo.tokenId);
-    }
-
-
-    /**
-     * 
-     * @param nftAddress The nft address pegged to the erc20
-     * @param to The reciver of the erc20
-     * @param amount The amount of erc20 to transfer
-     * 
-     * @dev you can use this function to transfer nft franctions 100% securily and registered by te contract
-     */
-
-    function transferErcTokens(address nftAddress,address to, uint256 amount) external {
-        
-        if(nftAddress == address(0)) {
-            revert TokenDivider__NftAddressIsZero();
-        }
-
-        if(to == address(0)) {
-            revert TokenDivider__CantTransferToAddressZero();
-        }
-
-        if(amount == 0) {
-            revert TokenDivider__AmountCantBeZero();
-        }
-
-        ERC20Info memory tokenInfo = nftToErc20Info[nftAddress];
-
-        if(to == address(0)) {
-            revert TokenDivider__CantTransferToAddressZero();
-        }
-        if(balances[msg.sender][tokenInfo.erc20Address] < amount) {
-            revert TokenDivider__NotEnoughErc20Balance();
-        }
-
-        balances[msg.sender][tokenInfo.erc20Address] -= amount;
-        balances[to][tokenInfo.erc20Address] += amount;
-
-        emit TokensTransfered(amount, tokenInfo.erc20Address);
-
-        IERC20(tokenInfo.erc20Address).transferFrom(msg.sender,to, amount);
-    }
-
-    /**
-     * 
-     * @param nftPegged The nft address pegged to the tokens to sell
-     * @param price The price of all the tokens to sell
-     * @param amount  The amount of tokens to sell
-     * 
-     * @dev this function creates a new order, is like publish you assets into a marketplace, where other persons can buy it.
-     * firstly, once you call this function, the amount of tokens that you passed into as a parameter, get blocked,  by sending it 
-     * to this contract, then a new order is created and published.
-     */
-
-    function sellErc20(address nftPegged, uint256 price,uint256 amount) external {
-        if(nftPegged == address(0)) {
-            revert TokenDivider__NftAddressIsZero();
-        }
-
-        if( amount == 0) {
-            revert TokenDivider__AmountCantBeZero();
-        }
-        
-        ERC20Info memory tokenInfo = nftToErc20Info[nftPegged]; 
-        if(balances[msg.sender][tokenInfo.erc20Address] < amount) {
-            revert TokenDivider__InsuficientBalance();
-        }
-
-        balances[msg.sender][tokenInfo.erc20Address] -= amount;
-
-        s_userToSellOrders[msg.sender].push(
-             SellOrder({
-                seller: msg.sender,
-                erc20Address: tokenInfo.erc20Address,
-                price: price,
-                amount: amount
-            })
-        );
-
-        emit OrderPublished(amount,msg.sender, nftPegged);
-
-        IERC20(tokenInfo.erc20Address).transferFrom(msg.sender,address(this), amount);
-    }
-    
-
-    /**
-     * 
-     * @param orderIndex The index of the order in all the orders array of the seller (the seller can have multiple orders active)
-     * @param seller The person who is selling this tokens
-     * 
-     * @dev when the buyer call this function, the eth or any token accepted to pay, is sent to the seller
-     * if the transfer executed correctly, then this contract, wich has all the tokens, send the tokens to the msg.sender
-     */
-
-    function buyOrder(uint256 orderIndex, address seller) external payable {
-        if(seller == address(0)) {
-            revert TokenDivider__InvalidSeller();
-        }
-
-        
-        
-        SellOrder memory order = s_userToSellOrders[seller][orderIndex];
-
-        if(msg.value < order.price) {
-            revert TokenDivider__IncorrectEtherAmount();
-        }
-
-        uint256 fee = order.price / 100;
-        uint256 sellerFee = fee / 2;
-
-
-        if(msg.value <  order.price + sellerFee) {
-            revert TokenDivider__InsuficientEtherForFees();
-        }
-
-
-        balances[msg.sender][order.erc20Address] += order.amount;
-
-        s_userToSellOrders[seller][orderIndex] = s_userToSellOrders[seller][s_userToSellOrders[seller].length - 1];
-        s_userToSellOrders[seller].pop();
-        
-        emit OrderSelled(msg.sender, order.price);
-        
-        // Transfer The Ether
-
-        (bool success, ) = payable(order.seller).call{value: (order.price - sellerFee)}("");
-
-        if(!success) {
-            revert TokenDivider__TransferFailed();
-        }
-
-        (bool taxSuccess, ) = payable(owner()).call{value: fee}("");
-
-
-        if(!taxSuccess) {
-            revert TokenDivider__TransferFailed();
-        }
-
-        IERC20(order.erc20Address).transfer(msg.sender, order.amount); 
-
-    }
-
-    /** Getters */
-
-    function getBalanceOf(address user, address token) public view returns(uint256) {
-        return balances[user][token];
-    }
-
-    function getErc20TotalMintedAmount(address erc20) public view returns(uint256) {
-        return erc20ToMintedAmount[erc20];
-    }
-
-    function getErc20InfoFromNft(address nft) public view returns(ERC20Info memory) {
-        return nftToErc20Info[nft];
-    }
-
-    function getOrderPrice(address seller, uint256 index) public view returns(uint256 price) {
-        price =  s_userToSellOrders[seller][index].price;
-    }
-
-}
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.18;
+
+import {IERC20} from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import {ERC20ToGenerateNftFraccion} from "src/token/ERC20ToGenerateNftFraccion.sol";
+import {IERC721, ERC721} from "@openzeppelin/contracts/token/ERC721/ERC721.sol";
+import {IERC721Receiver} from "@openzeppelin/contracts/token/ERC721/IERC721Receiver.sol";
+import {Ownable} from "@openzeppelin/contracts/access/Ownable.sol";
+
+/**
+ * @title TokenDivider
+ * @author Juan Pedro Ventura Baltian, 14 years old
+ * @notice This contracts was created, with the intention to make a new market of nft franctions
+ * There are a function to divide an nft, then you can sell and buy some fraction of nft, that are basicaly
+ * erc20 tokens, each nft pegged to an nft.There are some validations, to make the platforme the most secure
+ * as possible.This is the first project that i code alone, in blockchain, foundry and solidity.
+ * Thank you so much for read it.
+ */
+contract TokenDivider is IERC721Receiver, Ownable {
+    error TokenDivider__NotFromNftOwner();
+    error TokenDivider__NotEnoughErc20Balance();
+    error TokenDivider__NftTransferFailed();
+    error TokenDivider__InsuficientBalance();
+    error TokenDivider__CantTransferToAddressZero();
+    error TokenDivider__TransferFailed();
+    error TokenDivider__NftAddressIsZero();
+    error TokenDivider__AmountCantBeZero();
+    error TokenDivider__InvalidSeller();
+    error TokenDivier__InvalidAmount();
+    error TokenDivider__IncorrectEtherAmount();
+    error TokenDivider__InsuficientEtherForFees();
+
+    struct ERC20Info {
+        address erc20Address;
+        uint256 tokenId;
+    }
+
+    struct SellOrder {
+        address seller;
+        address erc20Address;
+        uint256 price;
+        uint256 amount;
+    }
+
+    /**
+     * @dev balances Relates a user with an amount of a erc20 token, this erc20 tokens is an nft fraction
+     *
+     *  @dev nftToErc20Info Relates an nft with the erc20 pegged, and othe data like the erc20 amount, or the tokenId
+     *
+     *  @dev s_userToSellOrders Relates a user with an array of sell orders, that each sell order 
+     *  has a seller, an erc20 that is the token to sell, a price and an amount of erc20 to sell
+     */
+    mapping(address user => mapping(address erc20Address => uint256 amount)) balances;
+    mapping(address nft => ERC20Info) nftToErc20Info;
+    mapping(address user => SellOrder[] orders) s_userToSellOrders;
+    mapping(address erc20 => address nft) erc20ToNft;
+    mapping(address erc20 => uint256 totalErc20Minted) erc20ToMintedAmount;
+
+    event NftDivided(address indexed nftAddress, uint256 indexed amountErc20Minted, address indexed erc20Minted);
+    event NftClaimed(address indexed nftAddress);
+    event TokensTransfered(uint256 indexed amount, address indexed erc20Address);
+    event OrderPublished(uint256 indexed amount, address indexed seller, address indexed nftPegged);
+    event OrderSelled(address indexed buyer, uint256 price);
+
+    /**
+     *
+     *  Only the owner of the nft can call a function with this modifier
+     */
+    modifier onlyNftOwner(address nft, uint256 tokenId) {
+        if (msg.sender != IERC721(nft).ownerOf(tokenId)) {
+            revert TokenDivider__NotFromNftOwner();
+        }
+        _;
+    }
+
+    constructor() Ownable(msg.sender) {}
+
+    /**
+     * @dev Handles the receipt of an ERC721 token. This function is called whenever an ERC721 token is transferred to this contract.
+     */
+    function onERC721Received(
+        address, /* operator */
+        address, /* from */
+        uint256, /*  tokenId */
+        bytes calldata /* data */
+    ) external pure override returns (bytes4) {
+        // Return this value to confirm the receipt of the NFT
+        return this.onERC721Received.selector;
+    }
+
+    /**
+     *
+     * @param nftAddress The addres of the nft to divide
+     * @param tokenId The id of the token to divide
+     * @param amount The amount of erc20 tokens to mint for the nft
+     *
+     * @dev in this function, the nft passed as parameter, is locked by transfering it to this contract, then, it gives to the
+     * person calling this function an amount of erc20, beeing like a fraction of this nft.
+     */
+    function divideNft(address nftAddress, uint256 tokenId, uint256 amount)
+        external
+        onlyNftOwner(nftAddress, tokenId)
+        onlyNftOwner(nftAddress, tokenId)
+    {
+        if (nftAddress == address(0)) revert TokenDivider__NftAddressIsZero();
+        if (amount == 0) revert TokenDivider__AmountCantBeZero();
+	// @audit: there is no checking of inExistence tokenId, it might handled on modifier but need to check
+	// @audit-report: dependency has its own check
+
+        ERC20ToGenerateNftFraccion erc20Contract = new ERC20ToGenerateNftFraccion(
+            string(abi.encodePacked(ERC721(nftAddress).name(), "Fraccion")),
+            string(abi.encodePacked("F", ERC721(nftAddress).symbol()))
+        );
+
+	// @audit: can we mint again? out of this function?
+	// @audit-finding: low
+	// @audit-report: yes it can be minted again. It should not be able to do so.
+	// @audit-report: but so far this contract only handle the recorded ERC20 transactions
+        erc20Contract.mint(address(this), amount);
+        address erc20 = address(erc20Contract);
+
+        IERC721(nftAddress).safeTransferFrom(msg.sender, address(this), tokenId, "");
+
+	// @audit: what if we send the NFT to other address during this period?
+	// @audit-report: you cannot send the NFT to other address, related to unit testing test_failIf_sendNFTDuringDivide
+        if (IERC721(nftAddress).ownerOf(tokenId) == msg.sender) revert TokenDivider__NftTransferFailed();
+
+        balances[msg.sender][erc20] = amount;
+	// @audit: what happen if the given nft address already registered in this CA, then another token id register again?
+	// @audit-finding: high (critical)
+	// @audit-report: it overrides the previous divided NFT. The previously ERC20 tokens of divided NFT is no longer usable.
+        nftToErc20Info[nftAddress] = ERC20Info({erc20Address: erc20, tokenId: tokenId});
+        erc20ToMintedAmount[erc20] = amount;
+        erc20ToNft[erc20] = nftAddress;
+
+        emit NftDivided(nftAddress, amount, erc20);
+
+        bool transferSuccess = IERC20(erc20).transfer(msg.sender, amount);
+        if (!transferSuccess) {
+            revert TokenDivider__TransferFailed();
+        }
+    }
+
+    /**
+     *
+     * @param nftAddress  The address of the nft to claim
+     *
+     * @dev in this function, if you have all the erc20 minted for the nft, you can call this function to claim the nft,
+     * giving to the contract all the erc20 and it will give you back the nft
+     */
+    function claimNft(address nftAddress) external {
+	// @audit: check with "counterfeit" token
+	// @audit-report: the "counterfeit" or extra minted token is not registered in this contract so its not working. tested test_failIf_claimNftWithCounterfeitNFT
+        if (nftAddress == address(0)) {
+            revert TokenDivider__NftAddressIsZero();
+        }
+
+	// @audit: what if the nft address is not stored?
+	// @audit-report: it returns weird error but you can't claim nft with inexistence nft address test_failIf_notExistingNftAddress
+        ERC20Info storage tokenInfo = nftToErc20Info[nftAddress];
+
+        if (balances[msg.sender][tokenInfo.erc20Address] < erc20ToMintedAmount[tokenInfo.erc20Address]) {
+            revert TokenDivider__NotEnoughErc20Balance();
+        }
+
+	// @audit: what if token already sent to other address through ERC20 send function
+	// @audit-report: there is an error which doesn't procceed the transaction further and it reverts
+        ERC20ToGenerateNftFraccion(tokenInfo.erc20Address).burnFrom(
+            msg.sender, erc20ToMintedAmount[tokenInfo.erc20Address]
+        );
+
+        balances[msg.sender][tokenInfo.erc20Address] = 0;
+        erc20ToMintedAmount[tokenInfo.erc20Address] = 0;
+
+        emit NftClaimed(nftAddress);
+
+	// @audit: what happen if there is overlaps in same NFT address with different token id? will someone get a different NFT?
+	// @audit-finding: high
+	// @audit-report: you cannot claim the previous NFT with a weird error
+        IERC721(nftAddress).safeTransferFrom(address(this), msg.sender, tokenInfo.tokenId);
+    }
+
+    /**
+     *
+     * @param nftAddress The nft address pegged to the erc20
+     * @param to The reciver of the erc20
+     * @param amount The amount of erc20 to transfer
+     *
+     * @dev you can use this function to transfer nft franctions 100% securily and registered by te contract
+     */
+    function transferErcTokens(address nftAddress, address to, uint256 amount) external {
+	// @audit: check with "counterfeit" token
+        if (nftAddress == address(0)) {
+            revert TokenDivider__NftAddressIsZero();
+        }
+
+        if (to == address(0)) {
+            revert TokenDivider__CantTransferToAddressZero();
+        }
+
+        if (amount == 0) {
+            revert TokenDivider__AmountCantBeZero();
+        }
+
+        ERC20Info memory tokenInfo = nftToErc20Info[nftAddress];
+
+        if (to == address(0)) {
+            revert TokenDivider__CantTransferToAddressZero();
+        }
+        if (balances[msg.sender][tokenInfo.erc20Address] < amount) {
+            revert TokenDivider__NotEnoughErc20Balance();
+        }
+
+        balances[msg.sender][tokenInfo.erc20Address] -= amount;
+        balances[to][tokenInfo.erc20Address] += amount;
+
+        emit TokensTransfered(amount, tokenInfo.erc20Address);
+
+        IERC20(tokenInfo.erc20Address).transferFrom(msg.sender, to, amount);
+    }
+
+    /**
+     *
+     * @param nftPegged The nft address pegged to the tokens to sell
+     * @param price The price of all the tokens to sell
+     * @param amount  The amount of tokens to sell
+     *
+     * @dev this function creates a new order, is like publish you assets into a marketplace, where other persons can buy it.
+     * firstly, once you call this function, the amount of tokens that you passed into as a parameter, get blocked,  by sending it
+     * to this contract, then a new order is created and published.
+     */
+    function sellErc20(address nftPegged, uint256 price, uint256 amount) external {
+	// @audit: check with "counterfeit" token
+        if (nftPegged == address(0)) {
+            revert TokenDivider__NftAddressIsZero();
+        }
+
+        if (amount == 0) {
+            revert TokenDivider__AmountCantBeZero();
+        }
+	// @audit: no check for 0 price?
+	// @audit-report: no check but it successfully transfer the given amount without transfering the given ether
+
+        ERC20Info memory tokenInfo = nftToErc20Info[nftPegged];
+        if (balances[msg.sender][tokenInfo.erc20Address] < amount) {
+            revert TokenDivider__InsuficientBalance();
+        }
+
+        balances[msg.sender][tokenInfo.erc20Address] -= amount; // token amount reduced from its holder on sell order even tho no one buy it
+
+	// push sell order to array of sender
+        s_userToSellOrders[msg.sender].push(
+            SellOrder({seller: msg.sender, erc20Address: tokenInfo.erc20Address, price: price, amount: amount})
+        );
+
+        emit OrderPublished(amount, msg.sender, nftPegged);
+
+	// send erc20 token from owner to this contract
+	// @audit: what if the owner of ERC20 rejected this transaction?
+        IERC20(tokenInfo.erc20Address).transferFrom(msg.sender, address(this), amount);
+    }
+
+    /**
+     *
+     * @param orderIndex The index of the order in all the orders array of the seller (the seller can have multiple orders active)
+     * @param seller The person who is selling this tokens
+     *
+     * @dev when the buyer call this function, the eth or any token accepted to pay, is sent to the seller
+     * if the transfer executed correctly, then this contract, wich has all the tokens, send the tokens to the msg.sender
+     */
+    function buyOrder(uint256 orderIndex, address seller) external payable {
+	// @audit: check with "counterfeit" token
+        if (seller == address(0)) {
+            revert TokenDivider__InvalidSeller();
+        }
+
+        SellOrder memory order = s_userToSellOrders[seller][orderIndex];
+
+	// msg.value can be greater than order price?
+        if (msg.value < order.price) {
+            revert TokenDivider__IncorrectEtherAmount();
+        }
+
+	// if price 100, then fee is 1
+        uint256 fee = order.price / 100;
+	// if price 100, then seller fee is 0.5
+        uint256 sellerFee = fee / 2;
+
+        if (msg.value < order.price + sellerFee) {
+            revert TokenDivider__InsuficientEtherForFees();
+        }
+
+	// record erc20 amount on storage variable onchain
+        balances[msg.sender][order.erc20Address] += order.amount;
+
+	// override the current orderIndex with tail, then pop the tail out of array
+        s_userToSellOrders[seller][orderIndex] = s_userToSellOrders[seller][s_userToSellOrders[seller].length - 1];
+        s_userToSellOrders[seller].pop();
+
+        emit OrderSelled(msg.sender, order.price);
+
+        // Transfer The Ether
+
+	// send ether to seller, reduced with seller fee
+        (bool success,) = payable(order.seller).call{value: (order.price - sellerFee)}("");
+
+        if (!success) {
+            revert TokenDivider__TransferFailed();
+        }
+
+	// send "fee" to "owner"? 
+	// @audit: if buyer needs to pay price + seller fee. then seller is given price - seller fee. does fee is guarranted to be paid by buyer?
+	// @audit-report: yes it does. if the price is 0, then there is no value increase
+	// @audit: who owner?
+	// @audit-report: the deployer
+        (bool taxSuccess,) = payable(owner()).call{value: fee}("");
+
+        if (!taxSuccess) {
+            revert TokenDivider__TransferFailed();
+        }
+
+	// send erc20 token to buyer address
+        IERC20(order.erc20Address).transfer(msg.sender, order.amount);
+    }
+
+    /**
+     * Getters
+     */
+    function getBalanceOf(address user, address token) public view returns (uint256) {
+        return balances[user][token];
+    }
+
+    function getErc20TotalMintedAmount(address erc20) public view returns (uint256) {
+        return erc20ToMintedAmount[erc20];
+    }
+
+    function getErc20InfoFromNft(address nft) public view returns (ERC20Info memory) {
+        return nftToErc20Info[nft];
+    }
+
+    function getOrderPrice(address seller, uint256 index) public view returns (uint256 price) {
+        price = s_userToSellOrders[seller][index].price;
+    }
+}

test/unit/TokenDividerTest.audit.claimNft.t.sol

@@ -0,0 +1,293 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.18;
+
+import {Test} from 'forge-std/Test.sol';
+import {DeployTokenDivider} from 'script/DeployTokenDivider.s.sol';
+import {TokenDivider} from 'src/TokenDivider.sol';
+import {ERC721Mock} from '../mocks/ERC721Mock.sol';
+import {ERC20Mock} from '@openzeppelin/contracts/mocks/token/ERC20Mock.sol';
+
+contract TokenDividerClaimTest is Test {
+	DeployTokenDivider deployer;
+    TokenDivider tokenDivider;
+    ERC721Mock erc721Mock;
+
+	address public USER = makeAddr("user");
+    address public USER2 = makeAddr("user2");
+    uint256 constant public STARTING_USER_BALANCE = 10e18;
+    uint256 constant public AMOUNT = 2e18;
+    uint256 constant public TOKEN_ID = 0;
+
+	function setUp() public {
+        deployer = new DeployTokenDivider();
+        tokenDivider = deployer.run();
+        
+        erc721Mock = new ERC721Mock();
+        
+        erc721Mock.mint(USER);
+
+		// divide the ERC721 and mint ERC20
+		vm.startPrank(USER);
+		erc721Mock.approve(address(tokenDivider), TOKEN_ID);
+		tokenDivider.divideNft(
+			address(erc721Mock),
+			TOKEN_ID,
+			AMOUNT
+		);
+		vm.stopPrank();
+    }
+
+	function test_assertSetUp() public {
+        erc721Mock.mint(USER);
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);	
+
+		// assert if NFT already moved to tokenDivider
+        assertEq(
+			erc721Mock.ownerOf(TOKEN_ID),
+			address(tokenDivider)
+		);
+
+		// assert if USER has the ERC20 token
+			assertEq(
+			tokenDivider.getBalanceOf(USER,  address(erc20Mock)),
+			AMOUNT
+		);
+	}
+
+	function test_claimNftSuccessfully() public {
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+
+		vm.startPrank(USER);
+		erc20Mock.approve(address(tokenDivider), AMOUNT);
+		tokenDivider.claimNft(address(erc721Mock));
+		vm.stopPrank();
+
+		assertEq(
+			tokenDivider.getBalanceOf(
+				address(USER),
+				address(erc20Mock)
+			),
+			0			
+		);
+		assertEq(
+			tokenDivider.getErc20TotalMintedAmount(
+				address(erc20Mock)
+			),
+			0			
+		);
+		assertEq(
+			erc721Mock.ownerOf(TOKEN_ID),
+			address(USER)
+		);
+		assertEq(
+			erc20Mock.balanceOf(
+				address(USER)
+			),	
+			0
+		);
+	}
+
+	function test_failIf_claimNftWithCounterfeitNFT() public {
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+
+		vm.startPrank(USER2);
+		erc20Mock.mint(address(USER2), AMOUNT);
+		erc20Mock.approve(address(tokenDivider), AMOUNT);
+		vm.expectRevert(
+			TokenDivider.TokenDivider__NotEnoughErc20Balance.selector
+		);
+		tokenDivider.claimNft(address(erc721Mock));
+		vm.stopPrank();
+	}
+
+	function test_failIf_notExistingNftAddress() public {
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+
+		vm.startPrank(USER);
+		erc20Mock.approve(address(tokenDivider), AMOUNT);
+		tokenDivider.claimNft(address(1));
+		vm.stopPrank();
+
+		assertEq(
+			tokenDivider.getBalanceOf(
+				address(USER),
+				address(erc20Mock)
+			),
+			0			
+		);
+		assertEq(
+			tokenDivider.getErc20TotalMintedAmount(
+				address(erc20Mock)
+			),
+			0			
+		);
+		assertEq(
+			erc721Mock.ownerOf(TOKEN_ID),
+			address(USER)
+		);
+		assertEq(
+			erc20Mock.balanceOf(
+				address(USER)
+			),	
+			0
+		);
+	}
+
+	function test_failIf_ERC20SentToOtherOnClaim() public {
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+
+		assertEq(
+			erc20Mock.balanceOf(
+				address(USER)
+			),	
+			AMOUNT
+		);
+
+		vm.startPrank(USER);
+		erc20Mock.approve(address(tokenDivider), AMOUNT);
+		erc20Mock.transfer(
+			address(USER2),
+			AMOUNT
+		);
+		vm.stopPrank();
+
+		assertEq(
+			tokenDivider.getBalanceOf(
+				address(USER),
+				address(erc20Mock)
+			),
+			AMOUNT			
+		);
+		assertEq(
+			tokenDivider.getBalanceOf(
+				address(USER2),
+				address(erc20Mock)
+			),
+			0			
+		);
+
+		vm.startPrank(USER);
+		erc20Mock.approve(address(tokenDivider), AMOUNT);
+		vm.expectRevert();
+		tokenDivider.claimNft(address(erc721Mock));
+		vm.stopPrank();
+	}
+
+	function test_failIf_claimOverlappingNFTWithDifferentId() public {
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+
+		// mint ERC721 with new TOKEN_ID
+		erc721Mock.mint(USER2);
+		uint256 newTokenId = TOKEN_ID + 1;
+
+		vm.startPrank(USER2);
+		erc721Mock.approve(address(tokenDivider), newTokenId);
+		tokenDivider.divideNft(
+			address(erc721Mock),
+			newTokenId,
+			AMOUNT
+		);
+		vm.stopPrank();
+
+		ERC20Mock erc20MockWithNewTokenId = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+
+		// assert if NFT already moved to tokenDivider
+        assertEq(
+			erc721Mock.ownerOf(TOKEN_ID),
+			address(tokenDivider)
+		);
+		assertEq(
+			erc721Mock.ownerOf(newTokenId),
+			address(tokenDivider)
+		);
+		// assert if USER2 has the ERC20 token
+			assertEq(
+			tokenDivider.getBalanceOf(
+				USER2,
+				address(erc20MockWithNewTokenId)
+			),
+			AMOUNT
+		);
+
+		// USER2 claim NFT
+		vm.startPrank(USER2);
+		erc20MockWithNewTokenId.approve(
+			address(tokenDivider),
+			AMOUNT
+		);
+		tokenDivider.claimNft(address(erc721Mock));
+		vm.stopPrank();
+
+		assertEq(
+			erc721Mock.ownerOf(newTokenId),
+			address(USER2)
+		);
+		assertEq(
+			erc721Mock.ownerOf(TOKEN_ID),
+			address(tokenDivider)
+		);
+
+		// assert ERC20 address before USER claim NFT
+		// @audit-report: it returns different erc20 address
+		// @dev: feel free to uncomment to see the error
+		/*
+		assertEq(
+			address(
+				tokenDivider.getErc20InfoFromNft(
+					address(erc721Mock)
+				).erc20Address
+			),
+			address(erc20Mock)
+		);
+		 */
+
+		// USER claim NFT
+		vm.startPrank(USER2);
+		erc20MockWithNewTokenId.approve(
+			address(tokenDivider),
+			AMOUNT
+		);
+		// @dev: it weirdly returns ERC721InsufficientApproval
+		// despite its already approved in above.
+		// maybe because of different ERC20 address?
+		// @dev: changing the ERC20 address and the USER prank
+		// doesn't help
+		/*
+		tokenDivider.claimNft(address(erc721Mock));
+		vm.stopPrank();
+
+		assertEq(
+			erc721Mock.ownerOf(TOKEN_ID),
+			address(USER)
+		);
+		 */
+	}
+}

test/unit/TokenDividerTest.audit.divideNft.t.sol

@@ -0,0 +1,279 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.18;
+
+import {Test, console} from 'forge-std/Test.sol';
+import {DeployTokenDivider} from 'script/DeployTokenDivider.s.sol';
+import {TokenDivider} from 'src/TokenDivider.sol';
+import {ERC721Mock} from '../mocks/ERC721Mock.sol';
+import {ERC20Mock} from '@openzeppelin/contracts/mocks/token/ERC20Mock.sol';
+import {Ownable} from '@openzeppelin/contracts/access/Ownable.sol';
+
+contract TokenDividerDivideTest is Test {
+    DeployTokenDivider deployer;
+    TokenDivider tokenDivider;
+    ERC721Mock erc721Mock;
+
+    address public USER = makeAddr("user");
+    address public USER2 = makeAddr("user2");
+    uint256 constant public STARTING_USER_BALANCE = 10e18;
+    uint256 constant public AMOUNT = 2e18;
+    uint256 constant public TOKEN_ID = 0;
+
+    function setUp() public {
+        deployer = new DeployTokenDivider();
+        tokenDivider = deployer.run();
+        
+        erc721Mock = new ERC721Mock();
+        
+        erc721Mock.mint(USER); // @auditor: user has the NFT
+        vm.deal(USER2, STARTING_USER_BALANCE); // @auditor: user2 got 10 ether
+    }
+
+    function test_assertSetUp() public view {
+	// USER has the ERC721 NFT of TOKEN_ID
+	assertTrue(address(erc721Mock.ownerOf(TOKEN_ID)) == address(USER));
+
+	// USER2 has no ERC721 NFT of TOKEN_ID
+	assertTrue(address(erc721Mock.ownerOf(TOKEN_ID)) != address(USER2));
+    }
+
+    function test_divideNftSuccessfully() public {
+    	vm.startPrank(USER);
+
+	// approve the NFT to receive the NFT in USER
+        erc721Mock.approve(address(tokenDivider), TOKEN_ID);
+
+	tokenDivider.divideNft(
+		address(erc721Mock),
+		TOKEN_ID,
+		AMOUNT
+	);
+	vm.stopPrank();
+
+        ERC20Mock erc20Mock = ERC20Mock(
+		tokenDivider.getErc20InfoFromNft(address(erc721Mock)).erc20Address
+	);
+
+	// assert if NFT already moved to tokenDivider
+        assertEq(
+		erc721Mock.ownerOf(TOKEN_ID),
+		address(tokenDivider)
+	);
+	// assert if USER has the ERC20 token
+        assertEq(
+		tokenDivider.getBalanceOf(USER,  address(erc20Mock)),
+		AMOUNT
+	);
+    }
+
+    function test_failIf_sendNFTDuringDivide() public {
+    	vm.startPrank(USER);
+
+	// approve the NFT to receive the NFT in USER
+        erc721Mock.approve(address(tokenDivider), TOKEN_ID);
+
+	// send the NFT to USER2
+	erc721Mock.safeTransferFrom(
+		address(USER),
+		address(USER2),
+		TOKEN_ID
+	);
+
+	vm.expectRevert(
+		TokenDivider.TokenDivider__NotFromNftOwner.selector
+	);
+	tokenDivider.divideNft(
+		address(erc721Mock),
+		TOKEN_ID,
+		AMOUNT
+	);
+
+	vm.stopPrank();
+    }
+
+    function test_sendNFTBeforeDivide() public {
+    	vm.startPrank(USER);
+
+	// send the NFT to USER2
+	erc721Mock.safeTransferFrom(
+		address(USER),
+		address(USER2),
+		TOKEN_ID
+	);
+
+	vm.stopPrank();
+
+	vm.startPrank(USER2);
+
+	// approve the NFT to receive the NFT in USER
+        erc721Mock.approve(address(tokenDivider), TOKEN_ID);
+
+	tokenDivider.divideNft(
+		address(erc721Mock),
+		TOKEN_ID,
+		AMOUNT
+	);
+
+	vm.stopPrank();
+
+	ERC20Mock erc20Mock = ERC20Mock(
+		tokenDivider.getErc20InfoFromNft(address(erc721Mock)).erc20Address
+	);
+
+	// assert if USER2 has the ERC20 token
+        assertEq(
+		tokenDivider.getBalanceOf(USER2,  address(erc20Mock)),
+		AMOUNT
+	);
+    }
+    
+    function test_failIf_nonExistenceNftTokenId() public {
+    	vm.startPrank(USER);
+
+	// approve the NFT to receive the NFT in USER
+        erc721Mock.approve(address(tokenDivider), TOKEN_ID);
+
+	vm.expectRevert();
+	tokenDivider.divideNft(
+		address(erc721Mock),
+		404,
+		AMOUNT
+	);
+	vm.stopPrank();
+    }
+
+    function test_failWhen_reMintTheDividedERC20Token() public {
+    	vm.startPrank(USER);
+
+	// approve the NFT to receive the NFT in USER
+        erc721Mock.approve(address(tokenDivider), TOKEN_ID);
+
+	tokenDivider.divideNft(
+		address(erc721Mock),
+		TOKEN_ID,
+		AMOUNT
+	);
+	vm.stopPrank();
+
+        ERC20Mock erc20Mock = ERC20Mock(
+		tokenDivider.getErc20InfoFromNft(address(erc721Mock)).erc20Address
+	);
+
+	// assert if USER has the ERC20 token
+        assertEq(
+		tokenDivider.getBalanceOf(USER,  address(erc20Mock)),
+		AMOUNT
+	);
+
+	vm.startPrank(USER2);
+	erc20Mock.mint(address(USER2), AMOUNT);
+	vm.stopPrank();
+
+	assertEq(
+		tokenDivider.getBalanceOf(
+			USER, 
+			address(erc20Mock)
+		),
+		AMOUNT
+	);
+	assertEq(
+		tokenDivider.getBalanceOf(
+			USER2, 
+			address(erc20Mock)
+		),
+		erc20Mock.balanceOf(address(USER2))
+	);
+	assertEq(
+		erc20Mock.totalSupply(),
+		AMOUNT
+	);
+    }
+
+    function test_divideSameNFTAddressWithDifferentTokenId() public {
+    	vm.startPrank(USER);
+
+	// approve the NFT to receive the NFT in USER
+        erc721Mock.approve(address(tokenDivider), TOKEN_ID);
+
+	tokenDivider.divideNft(
+		address(erc721Mock),
+		TOKEN_ID,
+		AMOUNT
+	);
+	vm.stopPrank();
+
+        ERC20Mock erc20Mock = ERC20Mock(
+		tokenDivider.getErc20InfoFromNft(address(erc721Mock)).erc20Address
+	);
+
+	// assert if NFT already moved to tokenDivider
+        assertEq(
+		erc721Mock.ownerOf(TOKEN_ID),
+		address(tokenDivider)
+	);
+	// assert if USER has the ERC20 token
+        assertEq(
+		tokenDivider.getBalanceOf(USER,  address(erc20Mock)),
+		AMOUNT
+	);
+
+	uint256 counterfeitTokenId = TOKEN_ID + 1;
+	erc721Mock.mint(USER2);
+	assertEq(
+		erc721Mock.ownerOf(counterfeitTokenId),
+		address(USER2)
+	);
+
+	// USER2 divide the counterfeit
+	vm.startPrank(USER2);
+
+	// approve the NFT to receive the NFT in USER2
+        erc721Mock.approve(
+		address(tokenDivider),
+		counterfeitTokenId
+	);
+
+	tokenDivider.divideNft(
+		address(erc721Mock),
+		counterfeitTokenId,
+		AMOUNT
+	);
+	vm.stopPrank();
+
+	// now both of users (USER and USER2) has the same amount of registered ERC20 tokens despite it refer to different NFT Token Id
+
+	ERC20Mock erc20MockCounterfeit = ERC20Mock(
+		tokenDivider.getErc20InfoFromNft(address(erc721Mock)).erc20Address
+	);
+	// assert if NFT already moved to tokenDivider
+
+        assertEq(
+		erc721Mock.ownerOf(counterfeitTokenId),
+		address(tokenDivider)
+	);
+
+	// assert if previous NFT is still being hold by contract
+	assertEq(
+		erc721Mock.ownerOf(TOKEN_ID),
+		address(tokenDivider)
+	);
+
+	// assert if USER2 has the ERC20 token
+        assertEq(
+		tokenDivider.getBalanceOf(
+			USER2, 
+			address(erc20MockCounterfeit)
+	),
+		AMOUNT
+	);
+	// assert if USER has the ERC20 token
+        assertEq(
+		tokenDivider.getBalanceOf(
+			USER, 
+			address(erc20MockCounterfeit)
+	),
+		AMOUNT
+	);
+    }
+
+}

test/unit/TokenDividerTest.audit.sellErc20.t.sol

@@ -0,0 +1,237 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.18;
+
+import {Test} from 'forge-std/Test.sol';
+import {DeployTokenDivider} from 'script/DeployTokenDivider.s.sol';
+import {TokenDivider} from 'src/TokenDivider.sol';
+import {ERC721Mock} from '../mocks/ERC721Mock.sol';
+import {ERC20Mock} from '@openzeppelin/contracts/mocks/token/ERC20Mock.sol';
+
+contract TokenDividerSellTest is Test {
+	DeployTokenDivider deployer;
+    TokenDivider tokenDivider;
+    ERC721Mock erc721Mock;
+
+	address public USER = makeAddr("user");
+    address public USER2 = makeAddr("user2");
+    uint256 constant public STARTING_USER_BALANCE = 10e18;
+    uint256 constant public AMOUNT = 2e18;
+    uint256 constant public TOKEN_ID = 0;
+
+	function setUp() public {
+        deployer = new DeployTokenDivider();
+        tokenDivider = deployer.run();
+        
+        erc721Mock = new ERC721Mock();
+        
+        erc721Mock.mint(USER);
+
+		// divide the ERC721 and mint ERC20
+		vm.startPrank(USER);
+		erc721Mock.approve(address(tokenDivider), TOKEN_ID);
+		tokenDivider.divideNft(
+			address(erc721Mock),
+			TOKEN_ID,
+			AMOUNT
+		);
+		vm.stopPrank();
+    }
+
+	function test_assertSetUp() public {
+        erc721Mock.mint(USER);
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);	
+
+		// assert if NFT already moved to tokenDivider
+        assertEq(
+			erc721Mock.ownerOf(TOKEN_ID),
+			address(tokenDivider)
+		);
+
+		// assert if USER has the ERC20 token
+		assertEq(
+			tokenDivider.getBalanceOf(USER,  address(erc20Mock)),
+			AMOUNT
+		);
+	}
+
+	function test_sellErc20() public {
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+		
+		uint256 sellAmount = 1;
+		vm.startPrank(USER);
+		erc20Mock.approve(address(tokenDivider), sellAmount);
+		tokenDivider.sellErc20(
+			address(erc721Mock),
+			1,
+			sellAmount
+		);
+		vm.stopPrank();
+		
+		assertEq(
+			tokenDivider.getBalanceOf(USER,  address(erc20Mock)),
+			AMOUNT - 1
+		);
+	}
+
+	function test_sellErc20WithZeroPrice() public {
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+		
+		uint256 sellAmount = 1e17;
+		uint256 sellPrice = 0;
+		vm.startPrank(USER);
+		erc20Mock.approve(address(tokenDivider), sellAmount);
+		tokenDivider.sellErc20(
+			address(erc721Mock),
+			sellPrice,
+			sellAmount
+		);
+		vm.stopPrank();
+		
+		assertEq(
+			tokenDivider.getBalanceOf(USER,  address(erc20Mock)),
+			AMOUNT - sellAmount
+		);
+
+		assertEq(
+			sellPrice,
+			tokenDivider.getOrderPrice(
+				address(USER),
+				0 // index of order price
+			)
+		);
+	}
+
+	function test_sellAndBuyErc20() public {
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+		
+		uint256 sellAmount = 1e17;
+		uint256 sellPrice = 1 ether;
+		vm.startPrank(USER);
+		erc20Mock.approve(address(tokenDivider), sellAmount);
+		tokenDivider.sellErc20(
+			address(erc721Mock),
+			sellPrice,
+			sellAmount
+		);
+		vm.stopPrank();
+		
+		assertEq(
+			tokenDivider.getBalanceOf(USER,  address(erc20Mock)),
+			AMOUNT - sellAmount
+		);
+
+		uint256 buyPrice = sellPrice + ((sellPrice / 100) / 2);
+		vm.deal(
+			address(USER2),
+			buyPrice
+		);
+
+		uint256 contractInitialBalance = address(
+			tokenDivider.owner()
+		).balance;
+		assertEq(
+			address(USER).balance,
+			0
+		);
+
+		vm.startPrank(USER2);
+		tokenDivider.buyOrder{value: buyPrice}(
+			0,
+			address(USER)
+		);
+		vm.stopPrank();
+
+		assertEq(
+			erc20Mock.balanceOf(address(USER2)),
+			sellAmount
+		);
+		uint256 sellerFee = buyPrice - sellPrice;
+		assertEq(
+			address(
+				tokenDivider.owner()
+			).balance - contractInitialBalance,
+			sellerFee * 2
+		);
+		assertEq(
+			address(USER).balance,
+			sellPrice - sellerFee
+		);
+	}
+
+	function test_sellAndBuyErc20With0Price() public {
+		ERC20Mock erc20Mock = ERC20Mock(
+			tokenDivider.getErc20InfoFromNft(
+				address(erc721Mock)
+			).erc20Address
+		);
+		
+		uint256 sellAmount = 1e17;
+		uint256 sellPrice = 0 ether;
+		vm.startPrank(USER);
+		erc20Mock.approve(address(tokenDivider), sellAmount);
+		tokenDivider.sellErc20(
+			address(erc721Mock),
+			sellPrice,
+			sellAmount
+		);
+		vm.stopPrank();
+		
+		assertEq(
+			tokenDivider.getBalanceOf(USER,  address(erc20Mock)),
+			AMOUNT - sellAmount
+		);
+
+		uint256 buyPrice = sellPrice + ((sellPrice / 100) / 2);
+		vm.deal(
+			address(USER2),
+			buyPrice
+		);
+
+		uint256 contractInitialBalance = address(
+			tokenDivider.owner()
+		).balance;
+		assertEq(
+			address(USER).balance,
+			0
+		);
+
+		vm.startPrank(USER2);
+		tokenDivider.buyOrder{value: buyPrice}(
+			0,
+			address(USER)
+		);
+		vm.stopPrank();
+
+		assertEq(
+			erc20Mock.balanceOf(address(USER2)),
+			sellAmount
+		);
+		uint256 sellerFee = buyPrice - sellPrice;
+		assertEq(
+			address(
+				tokenDivider.owner()
+			).balance - contractInitialBalance,
+			sellerFee * 2
+		);
+		assertEq(
+			address(USER).balance,
+			sellPrice - sellerFee
+		);
+	}
+}

test/unit/TokenDividerTest.t.sol

@@ -27,8 +27,8 @@ contract TokenDiverTest is Test {
         
         erc721Mock = new ERC721Mock();
         
-        erc721Mock.mint(USER);
-        vm.deal(USER2, STARTING_USER_BALANCE);
+        erc721Mock.mint(USER); // @auditor: user has the NFT
+        vm.deal(USER2, STARTING_USER_BALANCE); // @auditor: user2 got 10 ether
     }
 
     function testDivideNft() public {
@@ -151,4 +151,4 @@ contract TokenDiverTest is Test {
             
         }
     }
-}
+}