Bundle ERC721 extensions into base contract (#2149)

* Add IERC721Metadata implementation into ERC721

* Add IERC721Enumerable into ERC721

* Update ERC721Pausable and ERC721Burnable

* Delete ERC721Metadata, ERC721Enumerable and ERC721 (now ERC721)

* Update mocks

* Update tests

* Update contracts/token/ERC721/ERC721.sol

Co-Authored-By: Francisco Giordano <frangio.1@gmail.com>

* Make ERC721Pausable and ERC721Burnable abstract

Co-authored-by: Francisco Giordano <frangio.1@gmail.com>

contracts/mocks/ERC721BurnableMock.sol

@@ -3,6 +3,8 @@ pragma solidity ^0.6.0;
 import "../token/ERC721/ERC721Burnable.sol";
 
 contract ERC721BurnableMock is ERC721Burnable {
+    constructor(string memory name, string memory symbol) public ERC721(name, symbol) { }
+
     function mint(address to, uint256 tokenId) public {
         _mint(to, tokenId);
     }

contracts/mocks/ERC721FullMock.sol

@@ -1,37 +0,0 @@
-pragma solidity ^0.6.0;
-
-import "../token/ERC721/ERC721Full.sol";
-import "../token/ERC721/ERC721Burnable.sol";
-
-/**
- * @title ERC721FullMock
- * This mock just provides public functions for setting metadata URI, getting all tokens of an owner,
- * checking token existence, removal of a token from an address
- */
-contract ERC721FullMock is ERC721Full, ERC721Burnable {
-    constructor (string memory name, string memory symbol) public ERC721Full(name, symbol) { }
-
-    function exists(uint256 tokenId) public view returns (bool) {
-        return _exists(tokenId);
-    }
-
-    function tokensOfOwner(address owner) public view returns (uint256[] memory) {
-        return _tokensOfOwner(owner);
-    }
-
-    function setTokenURI(uint256 tokenId, string memory uri) public {
-        _setTokenURI(tokenId, uri);
-    }
-
-    function setBaseURI(string memory baseURI) public {
-        _setBaseURI(baseURI);
-    }
-
-    function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal virtual override(ERC721, ERC721Full) {
-        super._beforeTokenTransfer(from, to, tokenId);
-    }
-
-    function mint(address to, uint256 tokenId) public {
-        _mint(to, tokenId);
-    }
-}

contracts/mocks/ERC721GSNRecipientMock.sol

@@ -9,7 +9,11 @@ import "../GSN/GSNRecipientSignature.sol";
  * A simple ERC721 mock that has GSN support enabled
  */
 contract ERC721GSNRecipientMock is ERC721, GSNRecipient, GSNRecipientSignature {
-    constructor(address trustedSigner) public GSNRecipientSignature(trustedSigner) { }
+    constructor(string memory name, string memory symbol, address trustedSigner)
+        public
+        ERC721(name, symbol)
+        GSNRecipientSignature(trustedSigner)
+    { }
 
     function mint(uint256 tokenId) public {
         _mint(_msgSender(), tokenId);

contracts/mocks/ERC721Mock.sol

@@ -7,18 +7,36 @@ import "../token/ERC721/ERC721.sol";
  * This mock just provides a public safeMint, mint, and burn functions for testing purposes
  */
 contract ERC721Mock is ERC721 {
-    function safeMint(address to, uint256 tokenId) public {
-        _safeMint(to, tokenId);
+    constructor (string memory name, string memory symbol) public ERC721(name, symbol) { }
+
+    function exists(uint256 tokenId) public view returns (bool) {
+        return _exists(tokenId);
     }
 
-    function safeMint(address to, uint256 tokenId, bytes memory _data) public {
-        _safeMint(to, tokenId, _data);
+    function tokensOfOwner(address owner) public view returns (uint256[] memory) {
+        return _tokensOfOwner(owner);
+    }
+
+    function setTokenURI(uint256 tokenId, string memory uri) public {
+        _setTokenURI(tokenId, uri);
+    }
+
+    function setBaseURI(string memory baseURI) public {
+        _setBaseURI(baseURI);
     }
 
     function mint(address to, uint256 tokenId) public {
         _mint(to, tokenId);
     }
 
+    function safeMint(address to, uint256 tokenId) public {
+        _safeMint(to, tokenId);
+    }
+
+    function safeMint(address to, uint256 tokenId, bytes memory _data) public {
+        _safeMint(to, tokenId, _data);
+    }
+
     function burn(uint256 tokenId) public {
         _burn(tokenId);
     }

contracts/mocks/ERC721PausableMock.sol

@@ -7,6 +7,8 @@ import "../token/ERC721/ERC721Pausable.sol";
  * This mock just provides a public mint, burn and exists functions for testing purposes
  */
 contract ERC721PausableMock is ERC721Pausable {
+    constructor (string memory name, string memory symbol) public ERC721(name, symbol) { }
+
     function mint(address to, uint256 tokenId) public {
         super._mint(to, tokenId);
     }

contracts/token/ERC721/ERC721.sol

@@ -2,17 +2,19 @@ pragma solidity ^0.6.0;
 
 import "../../GSN/Context.sol";
 import "./IERC721.sol";
+import "./IERC721Metadata.sol";
+import "./IERC721Enumerable.sol";
 import "./IERC721Receiver.sol";
+import "../../introspection/ERC165.sol";
 import "../../math/SafeMath.sol";
 import "../../utils/Address.sol";
 import "../../utils/Counters.sol";
-import "../../introspection/ERC165.sol";
 
 /**
  * @title ERC721 Non-Fungible Token Standard basic implementation
  * @dev see https://eips.ethereum.org/EIPS/eip-721
  */
-contract ERC721 is Context, ERC165, IERC721 {
+contract ERC721 is Context, ERC165, IERC721, IERC721Metadata, IERC721Enumerable {
     using SafeMath for uint256;
     using Address for address;
     using Counters for Counters.Counter;
@@ -33,6 +35,30 @@ contract ERC721 is Context, ERC165, IERC721 {
     // Mapping from owner to operator approvals
     mapping (address => mapping (address => bool)) private _operatorApprovals;
 
+    // Token name
+    string private _name;
+
+    // Token symbol
+    string private _symbol;
+
+    // Optional mapping for token URIs
+    mapping(uint256 => string) private _tokenURIs;
+
+    // Base URI
+    string private _baseURI;
+
+    // Mapping from owner to list of owned token IDs
+    mapping(address => uint256[]) private _ownedTokens;
+
+    // Mapping from token ID to index of the owner tokens list
+    mapping(uint256 => uint256) private _ownedTokensIndex;
+
+    // Array with all token ids, used for enumeration
+    uint256[] private _allTokens;
+
+    // Mapping from token id to position in the allTokens array
+    mapping(uint256 => uint256) private _allTokensIndex;
+
     /*
      *     bytes4(keccak256('balanceOf(address)')) == 0x70a08231
      *     bytes4(keccak256('ownerOf(uint256)')) == 0x6352211e
@@ -49,9 +75,32 @@ contract ERC721 is Context, ERC165, IERC721 {
      */
     bytes4 private constant _INTERFACE_ID_ERC721 = 0x80ac58cd;
 
-    constructor () public {
+    /*
+     *     bytes4(keccak256('name()')) == 0x06fdde03
+     *     bytes4(keccak256('symbol()')) == 0x95d89b41
+     *     bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd
+     *
+     *     => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd == 0x5b5e139f
+     */
+    bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;
+
+    /*
+     *     bytes4(keccak256('totalSupply()')) == 0x18160ddd
+     *     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59
+     *     bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7
+     *
+     *     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63
+     */
+    bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;
+
+    constructor (string memory name, string memory symbol) public {
+        _name = name;
+        _symbol = symbol;
+
         // register the supported interfaces to conform to ERC721 via ERC165
         _registerInterface(_INTERFACE_ID_ERC721);
+        _registerInterface(_INTERFACE_ID_ERC721_METADATA);
+        _registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
     }
 
     /**
@@ -77,6 +126,83 @@ contract ERC721 is Context, ERC165, IERC721 {
         return owner;
     }
 
+    /**
+     * @dev Gets the token name.
+     * @return string representing the token name
+     */
+    function name() external view override returns (string memory) {
+        return _name;
+    }
+
+    /**
+     * @dev Gets the token symbol.
+     * @return string representing the token symbol
+     */
+    function symbol() external view override returns (string memory) {
+        return _symbol;
+    }
+
+    /**
+     * @dev Returns the URI for a given token ID. May return an empty string.
+     *
+     * If the token's URI is non-empty and a base URI was set (via
+     * {_setBaseURI}), it will be added to the token ID's URI as a prefix.
+     *
+     * Reverts if the token ID does not exist.
+     */
+    function tokenURI(uint256 tokenId) external view override returns (string memory) {
+        require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");
+
+        string memory _tokenURI = _tokenURIs[tokenId];
+
+        // Even if there is a base URI, it is only appended to non-empty token-specific URIs
+        if (bytes(_tokenURI).length == 0) {
+            return "";
+        } else {
+            // abi.encodePacked is being used to concatenate strings
+            return string(abi.encodePacked(_baseURI, _tokenURI));
+        }
+    }
+
+    /**
+    * @dev Returns the base URI set via {_setBaseURI}. This will be
+    * automatically added as a preffix in {tokenURI} to each token's URI, when
+    * they are non-empty.
+    */
+    function baseURI() external view returns (string memory) {
+        return _baseURI;
+    }
+
+    /**
+     * @dev Gets the token ID at a given index of the tokens list of the requested owner.
+     * @param owner address owning the tokens list to be accessed
+     * @param index uint256 representing the index to be accessed of the requested tokens list
+     * @return uint256 token ID at the given index of the tokens list owned by the requested address
+     */
+    function tokenOfOwnerByIndex(address owner, uint256 index) public view override returns (uint256) {
+        require(index < balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
+        return _ownedTokens[owner][index];
+    }
+
+    /**
+     * @dev Gets the total amount of tokens stored by the contract.
+     * @return uint256 representing the total amount of tokens
+     */
+    function totalSupply() public view override returns (uint256) {
+        return _allTokens.length;
+    }
+
+    /**
+     * @dev Gets the token ID at a given index of all the tokens in this contract
+     * Reverts if the index is greater or equal to the total number of tokens.
+     * @param index uint256 representing the index to be accessed of the tokens list
+     * @return uint256 token ID at the given index of the tokens list
+     */
+    function tokenByIndex(uint256 index) public view override returns (uint256) {
+        require(index < totalSupply(), "ERC721Enumerable: global index out of bounds");
+        return _allTokens[index];
+    }
+
     /**
      * @dev Approves another address to transfer the given token ID
      * The zero address indicates there is no approved address.
@@ -260,6 +386,9 @@ contract ERC721 is Context, ERC165, IERC721 {
 
         _beforeTokenTransfer(address(0), to, tokenId);
 
+        _addTokenToOwnerEnumeration(to, tokenId);
+        _addTokenToAllTokensEnumeration(tokenId);
+
         _tokenOwner[tokenId] = to;
         _ownedTokensCount[to].increment();
 
@@ -276,6 +405,17 @@ contract ERC721 is Context, ERC165, IERC721 {
 
         _beforeTokenTransfer(owner, address(0), tokenId);
 
+        // Clear metadata (if any)
+        if (bytes(_tokenURIs[tokenId]).length != 0) {
+            delete _tokenURIs[tokenId];
+        }
+
+        _removeTokenFromOwnerEnumeration(owner, tokenId);
+        // Since tokenId will be deleted, we can clear its slot in _ownedTokensIndex to trigger a gas refund
+        _ownedTokensIndex[tokenId] = 0;
+
+        _removeTokenFromAllTokensEnumeration(tokenId);
+
         // Clear approvals
         _approve(address(0), tokenId);
 
@@ -298,6 +438,9 @@ contract ERC721 is Context, ERC165, IERC721 {
 
         _beforeTokenTransfer(from, to, tokenId);
 
+        _removeTokenFromOwnerEnumeration(from, tokenId);
+        _addTokenToOwnerEnumeration(to, tokenId);
+
         // Clear approvals
         _approve(address(0), tokenId);
 
@@ -309,6 +452,37 @@ contract ERC721 is Context, ERC165, IERC721 {
         emit Transfer(from, to, tokenId);
     }
 
+    /**
+     * @dev Internal function to set the token URI for a given token.
+     *
+     * Reverts if the token ID does not exist.
+     *
+     * TIP: If all token IDs share a prefix (for example, if your URIs look like
+     * `https://api.myproject.com/token/<id>`), use {_setBaseURI} to store
+     * it and save gas.
+     */
+    function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {
+        require(_exists(tokenId), "ERC721Metadata: URI set of nonexistent token");
+        _tokenURIs[tokenId] = _tokenURI;
+    }
+
+    /**
+     * @dev Internal function to set the base URI for all token IDs. It is
+     * automatically added as a prefix to the value returned in {tokenURI}.
+     */
+    function _setBaseURI(string memory baseURI_) internal virtual {
+        _baseURI = baseURI_;
+    }
+
+    /**
+     * @dev Gets the list of token IDs of the requested owner.
+     * @param owner address owning the tokens
+     * @return uint256[] List of token IDs owned by the requested address
+     */
+    function _tokensOfOwner(address owner) internal view returns (uint256[] storage) {
+        return _ownedTokens[owner];
+    }
+
     /**
      * @dev Internal function to invoke {IERC721Receiver-onERC721Received} on a target address.
      * The call is not executed if the target address is not a contract.
@@ -354,6 +528,81 @@ contract ERC721 is Context, ERC165, IERC721 {
         emit Approval(ownerOf(tokenId), to, tokenId);
     }
 
+    /**
+     * @dev Private function to add a token to this extension's ownership-tracking data structures.
+     * @param to address representing the new owner of the given token ID
+     * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
+     */
+    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
+        _ownedTokensIndex[tokenId] = _ownedTokens[to].length;
+        _ownedTokens[to].push(tokenId);
+    }
+
+    /**
+     * @dev Private function to add a token to this extension's token tracking data structures.
+     * @param tokenId uint256 ID of the token to be added to the tokens list
+     */
+    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
+        _allTokensIndex[tokenId] = _allTokens.length;
+        _allTokens.push(tokenId);
+    }
+
+    /**
+     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
+     * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
+     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
+     * This has O(1) time complexity, but alters the order of the _ownedTokens array.
+     * @param from address representing the previous owner of the given token ID
+     * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
+     */
+    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
+        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
+        // then delete the last slot (swap and pop).
+
+        uint256 lastTokenIndex = _ownedTokens[from].length.sub(1);
+        uint256 tokenIndex = _ownedTokensIndex[tokenId];
+
+        // When the token to delete is the last token, the swap operation is unnecessary
+        if (tokenIndex != lastTokenIndex) {
+            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];
+
+            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
+            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
+        }
+
+        // Deletes the contents at the last position of the array
+        _ownedTokens[from].pop();
+
+        // Note that _ownedTokensIndex[tokenId] hasn't been cleared: it still points to the old slot (now occupied by
+        // lastTokenId, or just over the end of the array if the token was the last one).
+    }
+
+    /**
+     * @dev Private function to remove a token from this extension's token tracking data structures.
+     * This has O(1) time complexity, but alters the order of the _allTokens array.
+     * @param tokenId uint256 ID of the token to be removed from the tokens list
+     */
+    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
+        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
+        // then delete the last slot (swap and pop).
+
+        uint256 lastTokenIndex = _allTokens.length.sub(1);
+        uint256 tokenIndex = _allTokensIndex[tokenId];
+
+        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
+        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
+        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
+        uint256 lastTokenId = _allTokens[lastTokenIndex];
+
+        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
+        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
+
+        // Delete the contents at the last position of the array
+        _allTokens.pop();
+
+        _allTokensIndex[tokenId] = 0;
+    }
+
     /**
      * @dev Hook that is called before any token transfer. This includes minting
      * and burning.

contracts/token/ERC721/ERC721Burnable.sol

@@ -7,7 +7,7 @@ import "./ERC721.sol";
  * @title ERC721 Burnable Token
  * @dev ERC721 Token that can be irreversibly burned (destroyed).
  */
-contract ERC721Burnable is Context, ERC721 {
+abstract contract ERC721Burnable is Context, ERC721 {
     /**
      * @dev Burns a specific ERC721 token.
      * @param tokenId uint256 id of the ERC721 token to be burned.

contracts/token/ERC721/ERC721Enumerable.sol

@@ -1,175 +0,0 @@
-pragma solidity ^0.6.0;
-
-import "../../GSN/Context.sol";
-import "./IERC721Enumerable.sol";
-import "./ERC721.sol";
-import "../../introspection/ERC165.sol";
-
-/**
- * @title ERC-721 Non-Fungible Token with optional enumeration extension logic
- * @dev See https://eips.ethereum.org/EIPS/eip-721
- */
-contract ERC721Enumerable is Context, ERC165, ERC721, IERC721Enumerable {
-    // Mapping from owner to list of owned token IDs
-    mapping(address => uint256[]) private _ownedTokens;
-
-    // Mapping from token ID to index of the owner tokens list
-    mapping(uint256 => uint256) private _ownedTokensIndex;
-
-    // Array with all token ids, used for enumeration
-    uint256[] private _allTokens;
-
-    // Mapping from token id to position in the allTokens array
-    mapping(uint256 => uint256) private _allTokensIndex;
-
-    /*
-     *     bytes4(keccak256('totalSupply()')) == 0x18160ddd
-     *     bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) == 0x2f745c59
-     *     bytes4(keccak256('tokenByIndex(uint256)')) == 0x4f6ccce7
-     *
-     *     => 0x18160ddd ^ 0x2f745c59 ^ 0x4f6ccce7 == 0x780e9d63
-     */
-    bytes4 private constant _INTERFACE_ID_ERC721_ENUMERABLE = 0x780e9d63;
-
-    /**
-     * @dev Constructor function.
-     */
-    constructor () public {
-        // register the supported interface to conform to ERC721Enumerable via ERC165
-        _registerInterface(_INTERFACE_ID_ERC721_ENUMERABLE);
-    }
-
-    /**
-     * @dev Gets the token ID at a given index of the tokens list of the requested owner.
-     * @param owner address owning the tokens list to be accessed
-     * @param index uint256 representing the index to be accessed of the requested tokens list
-     * @return uint256 token ID at the given index of the tokens list owned by the requested address
-     */
-    function tokenOfOwnerByIndex(address owner, uint256 index) public view override returns (uint256) {
-        require(index < balanceOf(owner), "ERC721Enumerable: owner index out of bounds");
-        return _ownedTokens[owner][index];
-    }
-
-    /**
-     * @dev Gets the total amount of tokens stored by the contract.
-     * @return uint256 representing the total amount of tokens
-     */
-    function totalSupply() public view override returns (uint256) {
-        return _allTokens.length;
-    }
-
-    /**
-     * @dev Gets the token ID at a given index of all the tokens in this contract
-     * Reverts if the index is greater or equal to the total number of tokens.
-     * @param index uint256 representing the index to be accessed of the tokens list
-     * @return uint256 token ID at the given index of the tokens list
-     */
-    function tokenByIndex(uint256 index) public view override returns (uint256) {
-        require(index < totalSupply(), "ERC721Enumerable: global index out of bounds");
-        return _allTokens[index];
-    }
-
-    function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal virtual override {
-        super._beforeTokenTransfer(from, to, tokenId);
-
-        if (from == address(0)) {
-            // When minting
-            _addTokenToOwnerEnumeration(to, tokenId);
-            _addTokenToAllTokensEnumeration(tokenId);
-        } else if (to == address(0)) {
-            // When burning
-            _removeTokenFromOwnerEnumeration(from, tokenId);
-            // Since tokenId will be deleted, we can clear its slot in _ownedTokensIndex to trigger a gas refund
-            _ownedTokensIndex[tokenId] = 0;
-
-            _removeTokenFromAllTokensEnumeration(tokenId);
-        } else {
-            _removeTokenFromOwnerEnumeration(from, tokenId);
-            _addTokenToOwnerEnumeration(to, tokenId);
-        }
-    }
-
-    /**
-     * @dev Gets the list of token IDs of the requested owner.
-     * @param owner address owning the tokens
-     * @return uint256[] List of token IDs owned by the requested address
-     */
-    function _tokensOfOwner(address owner) internal view returns (uint256[] storage) {
-        return _ownedTokens[owner];
-    }
-
-    /**
-     * @dev Private function to add a token to this extension's ownership-tracking data structures.
-     * @param to address representing the new owner of the given token ID
-     * @param tokenId uint256 ID of the token to be added to the tokens list of the given address
-     */
-    function _addTokenToOwnerEnumeration(address to, uint256 tokenId) private {
-        _ownedTokensIndex[tokenId] = _ownedTokens[to].length;
-        _ownedTokens[to].push(tokenId);
-    }
-
-    /**
-     * @dev Private function to add a token to this extension's token tracking data structures.
-     * @param tokenId uint256 ID of the token to be added to the tokens list
-     */
-    function _addTokenToAllTokensEnumeration(uint256 tokenId) private {
-        _allTokensIndex[tokenId] = _allTokens.length;
-        _allTokens.push(tokenId);
-    }
-
-    /**
-     * @dev Private function to remove a token from this extension's ownership-tracking data structures. Note that
-     * while the token is not assigned a new owner, the `_ownedTokensIndex` mapping is _not_ updated: this allows for
-     * gas optimizations e.g. when performing a transfer operation (avoiding double writes).
-     * This has O(1) time complexity, but alters the order of the _ownedTokens array.
-     * @param from address representing the previous owner of the given token ID
-     * @param tokenId uint256 ID of the token to be removed from the tokens list of the given address
-     */
-    function _removeTokenFromOwnerEnumeration(address from, uint256 tokenId) private {
-        // To prevent a gap in from's tokens array, we store the last token in the index of the token to delete, and
-        // then delete the last slot (swap and pop).
-
-        uint256 lastTokenIndex = _ownedTokens[from].length.sub(1);
-        uint256 tokenIndex = _ownedTokensIndex[tokenId];
-
-        // When the token to delete is the last token, the swap operation is unnecessary
-        if (tokenIndex != lastTokenIndex) {
-            uint256 lastTokenId = _ownedTokens[from][lastTokenIndex];
-
-            _ownedTokens[from][tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
-            _ownedTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
-        }
-
-        // Deletes the contents at the last position of the array
-        _ownedTokens[from].pop();
-
-        // Note that _ownedTokensIndex[tokenId] hasn't been cleared: it still points to the old slot (now occupied by
-        // lastTokenId, or just over the end of the array if the token was the last one).
-    }
-
-    /**
-     * @dev Private function to remove a token from this extension's token tracking data structures.
-     * This has O(1) time complexity, but alters the order of the _allTokens array.
-     * @param tokenId uint256 ID of the token to be removed from the tokens list
-     */
-    function _removeTokenFromAllTokensEnumeration(uint256 tokenId) private {
-        // To prevent a gap in the tokens array, we store the last token in the index of the token to delete, and
-        // then delete the last slot (swap and pop).
-
-        uint256 lastTokenIndex = _allTokens.length.sub(1);
-        uint256 tokenIndex = _allTokensIndex[tokenId];
-
-        // When the token to delete is the last token, the swap operation is unnecessary. However, since this occurs so
-        // rarely (when the last minted token is burnt) that we still do the swap here to avoid the gas cost of adding
-        // an 'if' statement (like in _removeTokenFromOwnerEnumeration)
-        uint256 lastTokenId = _allTokens[lastTokenIndex];
-
-        _allTokens[tokenIndex] = lastTokenId; // Move the last token to the slot of the to-delete token
-        _allTokensIndex[lastTokenId] = tokenIndex; // Update the moved token's index
-
-        // Delete the contents at the last position of the array
-        _allTokens.pop();
-
-        _allTokensIndex[tokenId] = 0;
-    }
-}

contracts/token/ERC721/ERC721Full.sol

@@ -1,23 +0,0 @@
-pragma solidity ^0.6.0;
-
-import "./ERC721Enumerable.sol";
-import "./ERC721Metadata.sol";
-
-/**
- * @title Full ERC721 Token
- * @dev This implementation includes all the required and some optional functionality of the ERC721 standard
- * Moreover, it includes approve all functionality using operator terminology.
- *
- * See https://eips.ethereum.org/EIPS/eip-721
- */
-contract ERC721Full is ERC721Enumerable, ERC721Metadata {
-    constructor (string memory name, string memory symbol) public ERC721Metadata(name, symbol) { }
-
-    function _beforeTokenTransfer(address from, address to, uint256 tokenId)
-        virtual
-        override(ERC721Enumerable, ERC721Metadata)
-        internal
-    {
-        super._beforeTokenTransfer(from, to, tokenId);
-    }
-}

contracts/token/ERC721/ERC721Metadata.sol

@@ -1,121 +0,0 @@
-pragma solidity ^0.6.0;
-
-import "../../GSN/Context.sol";
-import "./ERC721.sol";
-import "./IERC721Metadata.sol";
-import "../../introspection/ERC165.sol";
-
-contract ERC721Metadata is Context, ERC165, ERC721, IERC721Metadata {
-    // Token name
-    string private _name;
-
-    // Token symbol
-    string private _symbol;
-
-    // Optional mapping for token URIs
-    mapping(uint256 => string) private _tokenURIs;
-
-    // Base URI
-    string private _baseURI;
-
-    /*
-     *     bytes4(keccak256('name()')) == 0x06fdde03
-     *     bytes4(keccak256('symbol()')) == 0x95d89b41
-     *     bytes4(keccak256('tokenURI(uint256)')) == 0xc87b56dd
-     *
-     *     => 0x06fdde03 ^ 0x95d89b41 ^ 0xc87b56dd == 0x5b5e139f
-     */
-    bytes4 private constant _INTERFACE_ID_ERC721_METADATA = 0x5b5e139f;
-
-    /**
-     * @dev Constructor function
-     */
-    constructor (string memory name, string memory symbol) public {
-        _name = name;
-        _symbol = symbol;
-
-        // register the supported interfaces to conform to ERC721 via ERC165
-        _registerInterface(_INTERFACE_ID_ERC721_METADATA);
-    }
-
-    /**
-     * @dev Gets the token name.
-     * @return string representing the token name
-     */
-    function name() external view override returns (string memory) {
-        return _name;
-    }
-
-    /**
-     * @dev Gets the token symbol.
-     * @return string representing the token symbol
-     */
-    function symbol() external view override returns (string memory) {
-        return _symbol;
-    }
-
-    /**
-     * @dev Returns the URI for a given token ID. May return an empty string.
-     *
-     * If the token's URI is non-empty and a base URI was set (via
-     * {_setBaseURI}), it will be added to the token ID's URI as a prefix.
-     *
-     * Reverts if the token ID does not exist.
-     */
-    function tokenURI(uint256 tokenId) external view override returns (string memory) {
-        require(_exists(tokenId), "ERC721Metadata: URI query for nonexistent token");
-
-        string memory _tokenURI = _tokenURIs[tokenId];
-
-        // Even if there is a base URI, it is only appended to non-empty token-specific URIs
-        if (bytes(_tokenURI).length == 0) {
-            return "";
-        } else {
-            // abi.encodePacked is being used to concatenate strings
-            return string(abi.encodePacked(_baseURI, _tokenURI));
-        }
-    }
-
-    /**
-     * @dev Internal function to set the token URI for a given token.
-     *
-     * Reverts if the token ID does not exist.
-     *
-     * TIP: if all token IDs share a prefix (e.g. if your URIs look like
-     * `http://api.myproject.com/token/<id>`), use {_setBaseURI} to store
-     * it and save gas.
-     */
-    function _setTokenURI(uint256 tokenId, string memory _tokenURI) internal virtual {
-        require(_exists(tokenId), "ERC721Metadata: URI set of nonexistent token");
-        _tokenURIs[tokenId] = _tokenURI;
-    }
-
-    /**
-     * @dev Internal function to set the base URI for all token IDs. It is
-     * automatically added as a prefix to the value returned in {tokenURI}.
-     */
-    function _setBaseURI(string memory baseURI) internal virtual {
-        _baseURI = baseURI;
-    }
-
-    /**
-    * @dev Returns the base URI set via {_setBaseURI}. This will be
-    * automatically added as a preffix in {tokenURI} to each token's URI, when
-    * they are non-empty.
-    */
-    function baseURI() external view returns (string memory) {
-        return _baseURI;
-    }
-
-
-    function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal virtual override {
-        super._beforeTokenTransfer(from, to, tokenId);
-
-        if (to == address(0)) { // When burning tokens
-            // Clear metadata (if any)
-            if (bytes(_tokenURIs[tokenId]).length != 0) {
-                delete _tokenURIs[tokenId];
-            }
-        }
-    }
-}

contracts/token/ERC721/ERC721Pausable.sol

@@ -7,7 +7,7 @@ import "../../utils/Pausable.sol";
  * @title ERC721 Non-Fungible Pausable token
  * @dev ERC721 modified with pausable transfers.
  */
-contract ERC721Pausable is ERC721, Pausable {
+abstract contract ERC721Pausable is ERC721, Pausable {
     function _beforeTokenTransfer(address from, address to, uint256 tokenId) internal virtual override {
         super._beforeTokenTransfer(from, to, tokenId);
 

contracts/token/ERC721/IERC721Full.sol

@@ -1,11 +0,0 @@
-pragma solidity ^0.6.0;
-
-import "./IERC721.sol";
-import "./IERC721Enumerable.sol";
-import "./IERC721Metadata.sol";
-
-/**
- * @title ERC-721 Non-Fungible Token Standard, full implementation interface
- * @dev See https://eips.ethereum.org/EIPS/eip-721
- */
-abstract contract IERC721Full is IERC721, IERC721Enumerable, IERC721Metadata { }

test/GSN/ERC721GSNRecipientMock.test.js

@@ -11,10 +11,12 @@ const ERC721GSNRecipientMock = contract.fromArtifact('ERC721GSNRecipientMock');
 describe('ERC721GSNRecipient (integration)', function () {
   const [ signer, sender ] = accounts;
 
+  const name = 'Non Fungible Token';
+  const symbol = 'NFT';
   const tokenId = '42';
 
   beforeEach(async function () {
-    this.token = await ERC721GSNRecipientMock.new(signer);
+    this.token = await ERC721GSNRecipientMock.new(name, symbol, signer);
   });
 
   async function testMintToken (token, from, tokenId, options = {}) {

test/token/ERC721/ERC721.behavior.js

@@ -1,628 +0,0 @@
-const { contract } = require('@openzeppelin/test-environment');
-const { BN, constants, expectEvent, expectRevert } = require('@openzeppelin/test-helpers');
-const { expect } = require('chai');
-const { ZERO_ADDRESS } = constants;
-const { shouldSupportInterfaces } = require('../../introspection/SupportsInterface.behavior');
-
-const ERC721Mock = contract.fromArtifact('ERC721Mock');
-const ERC721ReceiverMock = contract.fromArtifact('ERC721ReceiverMock');
-
-function shouldBehaveLikeERC721 (
-  [owner, approved, anotherApproved, operator, other]
-) {
-  const firstTokenId = new BN(1);
-  const secondTokenId = new BN(2);
-  const unknownTokenId = new BN(3);
-  const RECEIVER_MAGIC_VALUE = '0x150b7a02';
-
-  describe('like an ERC721', function () {
-    beforeEach(async function () {
-      await this.token.mint(owner, firstTokenId);
-      await this.token.mint(owner, secondTokenId);
-      this.toWhom = other; // default to anyone for toWhom in context-dependent tests
-    });
-
-    describe('balanceOf', function () {
-      context('when the given address owns some tokens', function () {
-        it('returns the amount of tokens owned by the given address', async function () {
-          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('2');
-        });
-      });
-
-      context('when the given address does not own any tokens', function () {
-        it('returns 0', async function () {
-          expect(await this.token.balanceOf(other)).to.be.bignumber.equal('0');
-        });
-      });
-
-      context('when querying the zero address', function () {
-        it('throws', async function () {
-          await expectRevert(
-            this.token.balanceOf(ZERO_ADDRESS), 'ERC721: balance query for the zero address'
-          );
-        });
-      });
-    });
-
-    describe('ownerOf', function () {
-      context('when the given token ID was tracked by this token', function () {
-        const tokenId = firstTokenId;
-
-        it('returns the owner of the given token ID', async function () {
-          expect(await this.token.ownerOf(tokenId)).to.be.equal(owner);
-        });
-      });
-
-      context('when the given token ID was not tracked by this token', function () {
-        const tokenId = unknownTokenId;
-
-        it('reverts', async function () {
-          await expectRevert(
-            this.token.ownerOf(tokenId), 'ERC721: owner query for nonexistent token'
-          );
-        });
-      });
-    });
-
-    describe('transfers', function () {
-      const tokenId = firstTokenId;
-      const data = '0x42';
-
-      let logs = null;
-
-      beforeEach(async function () {
-        await this.token.approve(approved, tokenId, { from: owner });
-        await this.token.setApprovalForAll(operator, true, { from: owner });
-      });
-
-      const transferWasSuccessful = function ({ owner, tokenId, approved }) {
-        it('transfers the ownership of the given token ID to the given address', async function () {
-          expect(await this.token.ownerOf(tokenId)).to.be.equal(this.toWhom);
-        });
-
-        it('clears the approval for the token ID', async function () {
-          expect(await this.token.getApproved(tokenId)).to.be.equal(ZERO_ADDRESS);
-        });
-
-        if (approved) {
-          it('emit only a transfer event', async function () {
-            expectEvent.inLogs(logs, 'Transfer', {
-              from: owner,
-              to: this.toWhom,
-              tokenId: tokenId,
-            });
-          });
-        } else {
-          it('emits only a transfer event', async function () {
-            expectEvent.inLogs(logs, 'Transfer', {
-              from: owner,
-              to: this.toWhom,
-              tokenId: tokenId,
-            });
-          });
-        }
-
-        it('adjusts owners balances', async function () {
-          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('1');
-        });
-
-        it('adjusts owners tokens by index', async function () {
-          if (!this.token.tokenOfOwnerByIndex) return;
-
-          expect(await this.token.tokenOfOwnerByIndex(this.toWhom, 0)).to.be.bignumber.equal(tokenId);
-
-          expect(await this.token.tokenOfOwnerByIndex(owner, 0)).to.be.bignumber.not.equal(tokenId);
-        });
-      };
-
-      const shouldTransferTokensByUsers = function (transferFunction) {
-        context('when called by the owner', function () {
-          beforeEach(async function () {
-            ({ logs } = await transferFunction.call(this, owner, this.toWhom, tokenId, { from: owner }));
-          });
-          transferWasSuccessful({ owner, tokenId, approved });
-        });
-
-        context('when called by the approved individual', function () {
-          beforeEach(async function () {
-            ({ logs } = await transferFunction.call(this, owner, this.toWhom, tokenId, { from: approved }));
-          });
-          transferWasSuccessful({ owner, tokenId, approved });
-        });
-
-        context('when called by the operator', function () {
-          beforeEach(async function () {
-            ({ logs } = await transferFunction.call(this, owner, this.toWhom, tokenId, { from: operator }));
-          });
-          transferWasSuccessful({ owner, tokenId, approved });
-        });
-
-        context('when called by the owner without an approved user', function () {
-          beforeEach(async function () {
-            await this.token.approve(ZERO_ADDRESS, tokenId, { from: owner });
-            ({ logs } = await transferFunction.call(this, owner, this.toWhom, tokenId, { from: operator }));
-          });
-          transferWasSuccessful({ owner, tokenId, approved: null });
-        });
-
-        context('when sent to the owner', function () {
-          beforeEach(async function () {
-            ({ logs } = await transferFunction.call(this, owner, owner, tokenId, { from: owner }));
-          });
-
-          it('keeps ownership of the token', async function () {
-            expect(await this.token.ownerOf(tokenId)).to.be.equal(owner);
-          });
-
-          it('clears the approval for the token ID', async function () {
-            expect(await this.token.getApproved(tokenId)).to.be.equal(ZERO_ADDRESS);
-          });
-
-          it('emits only a transfer event', async function () {
-            expectEvent.inLogs(logs, 'Transfer', {
-              from: owner,
-              to: owner,
-              tokenId: tokenId,
-            });
-          });
-
-          it('keeps the owner balance', async function () {
-            expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('2');
-          });
-
-          it('keeps same tokens by index', async function () {
-            if (!this.token.tokenOfOwnerByIndex) return;
-            const tokensListed = await Promise.all(
-              [0, 1].map(i => this.token.tokenOfOwnerByIndex(owner, i))
-            );
-            expect(tokensListed.map(t => t.toNumber())).to.have.members(
-              [firstTokenId.toNumber(), secondTokenId.toNumber()]
-            );
-          });
-        });
-
-        context('when the address of the previous owner is incorrect', function () {
-          it('reverts', async function () {
-            await expectRevert(
-              transferFunction.call(this, other, other, tokenId, { from: owner }),
-              'ERC721: transfer of token that is not own'
-            );
-          });
-        });
-
-        context('when the sender is not authorized for the token id', function () {
-          it('reverts', async function () {
-            await expectRevert(
-              transferFunction.call(this, owner, other, tokenId, { from: other }),
-              'ERC721: transfer caller is not owner nor approved'
-            );
-          });
-        });
-
-        context('when the given token ID does not exist', function () {
-          it('reverts', async function () {
-            await expectRevert(
-              transferFunction.call(this, owner, other, unknownTokenId, { from: owner }),
-              'ERC721: operator query for nonexistent token'
-            );
-          });
-        });
-
-        context('when the address to transfer the token to is the zero address', function () {
-          it('reverts', async function () {
-            await expectRevert(
-              transferFunction.call(this, owner, ZERO_ADDRESS, tokenId, { from: owner }),
-              'ERC721: transfer to the zero address'
-            );
-          });
-        });
-      };
-
-      describe('via transferFrom', function () {
-        shouldTransferTokensByUsers(function (from, to, tokenId, opts) {
-          return this.token.transferFrom(from, to, tokenId, opts);
-        });
-      });
-
-      describe('via safeTransferFrom', function () {
-        const safeTransferFromWithData = function (from, to, tokenId, opts) {
-          return this.token.methods['safeTransferFrom(address,address,uint256,bytes)'](from, to, tokenId, data, opts);
-        };
-
-        const safeTransferFromWithoutData = function (from, to, tokenId, opts) {
-          return this.token.methods['safeTransferFrom(address,address,uint256)'](from, to, tokenId, opts);
-        };
-
-        const shouldTransferSafely = function (transferFun, data) {
-          describe('to a user account', function () {
-            shouldTransferTokensByUsers(transferFun);
-          });
-
-          describe('to a valid receiver contract', function () {
-            beforeEach(async function () {
-              this.receiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, false);
-              this.toWhom = this.receiver.address;
-            });
-
-            shouldTransferTokensByUsers(transferFun);
-
-            it('should call onERC721Received', async function () {
-              const receipt = await transferFun.call(this, owner, this.receiver.address, tokenId, { from: owner });
-
-              await expectEvent.inTransaction(receipt.tx, ERC721ReceiverMock, 'Received', {
-                operator: owner,
-                from: owner,
-                tokenId: tokenId,
-                data: data,
-              });
-            });
-
-            it('should call onERC721Received from approved', async function () {
-              const receipt = await transferFun.call(this, owner, this.receiver.address, tokenId, { from: approved });
-
-              await expectEvent.inTransaction(receipt.tx, ERC721ReceiverMock, 'Received', {
-                operator: approved,
-                from: owner,
-                tokenId: tokenId,
-                data: data,
-              });
-            });
-
-            describe('with an invalid token id', function () {
-              it('reverts', async function () {
-                await expectRevert(
-                  transferFun.call(
-                    this,
-                    owner,
-                    this.receiver.address,
-                    unknownTokenId,
-                    { from: owner },
-                  ),
-                  'ERC721: operator query for nonexistent token'
-                );
-              });
-            });
-          });
-        };
-
-        describe('with data', function () {
-          shouldTransferSafely(safeTransferFromWithData, data);
-        });
-
-        describe('without data', function () {
-          shouldTransferSafely(safeTransferFromWithoutData, null);
-        });
-
-        describe('to a receiver contract returning unexpected value', function () {
-          it('reverts', async function () {
-            const invalidReceiver = await ERC721ReceiverMock.new('0x42', false);
-            await expectRevert(
-              this.token.safeTransferFrom(owner, invalidReceiver.address, tokenId, { from: owner }),
-              'ERC721: transfer to non ERC721Receiver implementer'
-            );
-          });
-        });
-
-        describe('to a receiver contract that throws', function () {
-          it('reverts', async function () {
-            const revertingReceiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, true);
-            await expectRevert(
-              this.token.safeTransferFrom(owner, revertingReceiver.address, tokenId, { from: owner }),
-              'ERC721ReceiverMock: reverting'
-            );
-          });
-        });
-
-        describe('to a contract that does not implement the required function', function () {
-          it('reverts', async function () {
-            const nonReceiver = this.token;
-            await expectRevert(
-              this.token.safeTransferFrom(owner, nonReceiver.address, tokenId, { from: owner }),
-              'ERC721: transfer to non ERC721Receiver implementer'
-            );
-          });
-        });
-      });
-    });
-
-    describe('safe mint', function () {
-      const fourthTokenId = new BN(4);
-      const tokenId = fourthTokenId;
-      const data = '0x42';
-
-      beforeEach(async function () {
-        this.ERC721Mock = await ERC721Mock.new();
-      });
-
-      describe('via safeMint', function () { // regular minting is tested in ERC721Mintable.test.js and others
-        it('should call onERC721Received — with data', async function () {
-          this.receiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, false);
-          const receipt = await this.ERC721Mock.safeMint(this.receiver.address, tokenId, data);
-
-          await expectEvent.inTransaction(receipt.tx, ERC721ReceiverMock, 'Received', {
-            from: ZERO_ADDRESS,
-            tokenId: tokenId,
-            data: data,
-          });
-        });
-
-        it('should call onERC721Received — without data', async function () {
-          this.receiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, false);
-          const receipt = await this.ERC721Mock.safeMint(this.receiver.address, tokenId);
-
-          await expectEvent.inTransaction(receipt.tx, ERC721ReceiverMock, 'Received', {
-            from: ZERO_ADDRESS,
-            tokenId: tokenId,
-          });
-        });
-
-        context('to a receiver contract returning unexpected value', function () {
-          it('reverts', async function () {
-            const invalidReceiver = await ERC721ReceiverMock.new('0x42', false);
-            await expectRevert(
-              this.ERC721Mock.safeMint(invalidReceiver.address, tokenId),
-              'ERC721: transfer to non ERC721Receiver implementer'
-            );
-          });
-        });
-
-        context('to a receiver contract that throws', function () {
-          it('reverts', async function () {
-            const revertingReceiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, true);
-            await expectRevert(
-              this.ERC721Mock.safeMint(revertingReceiver.address, tokenId),
-              'ERC721ReceiverMock: reverting'
-            );
-          });
-        });
-
-        context('to a contract that does not implement the required function', function () {
-          it('reverts', async function () {
-            const nonReceiver = this.token;
-            await expectRevert(
-              this.ERC721Mock.safeMint(nonReceiver.address, tokenId),
-              'ERC721: transfer to non ERC721Receiver implementer'
-            );
-          });
-        });
-      });
-    });
-
-    describe('approve', function () {
-      const tokenId = firstTokenId;
-
-      let logs = null;
-
-      const itClearsApproval = function () {
-        it('clears approval for the token', async function () {
-          expect(await this.token.getApproved(tokenId)).to.be.equal(ZERO_ADDRESS);
-        });
-      };
-
-      const itApproves = function (address) {
-        it('sets the approval for the target address', async function () {
-          expect(await this.token.getApproved(tokenId)).to.be.equal(address);
-        });
-      };
-
-      const itEmitsApprovalEvent = function (address) {
-        it('emits an approval event', async function () {
-          expectEvent.inLogs(logs, 'Approval', {
-            owner: owner,
-            approved: address,
-            tokenId: tokenId,
-          });
-        });
-      };
-
-      context('when clearing approval', function () {
-        context('when there was no prior approval', function () {
-          beforeEach(async function () {
-            ({ logs } = await this.token.approve(ZERO_ADDRESS, tokenId, { from: owner }));
-          });
-
-          itClearsApproval();
-          itEmitsApprovalEvent(ZERO_ADDRESS);
-        });
-
-        context('when there was a prior approval', function () {
-          beforeEach(async function () {
-            await this.token.approve(approved, tokenId, { from: owner });
-            ({ logs } = await this.token.approve(ZERO_ADDRESS, tokenId, { from: owner }));
-          });
-
-          itClearsApproval();
-          itEmitsApprovalEvent(ZERO_ADDRESS);
-        });
-      });
-
-      context('when approving a non-zero address', function () {
-        context('when there was no prior approval', function () {
-          beforeEach(async function () {
-            ({ logs } = await this.token.approve(approved, tokenId, { from: owner }));
-          });
-
-          itApproves(approved);
-          itEmitsApprovalEvent(approved);
-        });
-
-        context('when there was a prior approval to the same address', function () {
-          beforeEach(async function () {
-            await this.token.approve(approved, tokenId, { from: owner });
-            ({ logs } = await this.token.approve(approved, tokenId, { from: owner }));
-          });
-
-          itApproves(approved);
-          itEmitsApprovalEvent(approved);
-        });
-
-        context('when there was a prior approval to a different address', function () {
-          beforeEach(async function () {
-            await this.token.approve(anotherApproved, tokenId, { from: owner });
-            ({ logs } = await this.token.approve(anotherApproved, tokenId, { from: owner }));
-          });
-
-          itApproves(anotherApproved);
-          itEmitsApprovalEvent(anotherApproved);
-        });
-      });
-
-      context('when the address that receives the approval is the owner', function () {
-        it('reverts', async function () {
-          await expectRevert(
-            this.token.approve(owner, tokenId, { from: owner }), 'ERC721: approval to current owner'
-          );
-        });
-      });
-
-      context('when the sender does not own the given token ID', function () {
-        it('reverts', async function () {
-          await expectRevert(this.token.approve(approved, tokenId, { from: other }),
-            'ERC721: approve caller is not owner nor approved');
-        });
-      });
-
-      context('when the sender is approved for the given token ID', function () {
-        it('reverts', async function () {
-          await this.token.approve(approved, tokenId, { from: owner });
-          await expectRevert(this.token.approve(anotherApproved, tokenId, { from: approved }),
-            'ERC721: approve caller is not owner nor approved for all');
-        });
-      });
-
-      context('when the sender is an operator', function () {
-        beforeEach(async function () {
-          await this.token.setApprovalForAll(operator, true, { from: owner });
-          ({ logs } = await this.token.approve(approved, tokenId, { from: operator }));
-        });
-
-        itApproves(approved);
-        itEmitsApprovalEvent(approved);
-      });
-
-      context('when the given token ID does not exist', function () {
-        it('reverts', async function () {
-          await expectRevert(this.token.approve(approved, unknownTokenId, { from: operator }),
-            'ERC721: owner query for nonexistent token');
-        });
-      });
-    });
-
-    describe('setApprovalForAll', function () {
-      context('when the operator willing to approve is not the owner', function () {
-        context('when there is no operator approval set by the sender', function () {
-          it('approves the operator', async function () {
-            await this.token.setApprovalForAll(operator, true, { from: owner });
-
-            expect(await this.token.isApprovedForAll(owner, operator)).to.equal(true);
-          });
-
-          it('emits an approval event', async function () {
-            const { logs } = await this.token.setApprovalForAll(operator, true, { from: owner });
-
-            expectEvent.inLogs(logs, 'ApprovalForAll', {
-              owner: owner,
-              operator: operator,
-              approved: true,
-            });
-          });
-        });
-
-        context('when the operator was set as not approved', function () {
-          beforeEach(async function () {
-            await this.token.setApprovalForAll(operator, false, { from: owner });
-          });
-
-          it('approves the operator', async function () {
-            await this.token.setApprovalForAll(operator, true, { from: owner });
-
-            expect(await this.token.isApprovedForAll(owner, operator)).to.equal(true);
-          });
-
-          it('emits an approval event', async function () {
-            const { logs } = await this.token.setApprovalForAll(operator, true, { from: owner });
-
-            expectEvent.inLogs(logs, 'ApprovalForAll', {
-              owner: owner,
-              operator: operator,
-              approved: true,
-            });
-          });
-
-          it('can unset the operator approval', async function () {
-            await this.token.setApprovalForAll(operator, false, { from: owner });
-
-            expect(await this.token.isApprovedForAll(owner, operator)).to.equal(false);
-          });
-        });
-
-        context('when the operator was already approved', function () {
-          beforeEach(async function () {
-            await this.token.setApprovalForAll(operator, true, { from: owner });
-          });
-
-          it('keeps the approval to the given address', async function () {
-            await this.token.setApprovalForAll(operator, true, { from: owner });
-
-            expect(await this.token.isApprovedForAll(owner, operator)).to.equal(true);
-          });
-
-          it('emits an approval event', async function () {
-            const { logs } = await this.token.setApprovalForAll(operator, true, { from: owner });
-
-            expectEvent.inLogs(logs, 'ApprovalForAll', {
-              owner: owner,
-              operator: operator,
-              approved: true,
-            });
-          });
-        });
-      });
-
-      context('when the operator is the owner', function () {
-        it('reverts', async function () {
-          await expectRevert(this.token.setApprovalForAll(owner, true, { from: owner }),
-            'ERC721: approve to caller');
-        });
-      });
-    });
-
-    describe('getApproved', async function () {
-      context('when token is not minted', async function () {
-        it('reverts', async function () {
-          await expectRevert(
-            this.token.getApproved(unknownTokenId),
-            'ERC721: approved query for nonexistent token'
-          );
-        });
-      });
-
-      context('when token has been minted ', async function () {
-        it('should return the zero address', async function () {
-          expect(await this.token.getApproved(firstTokenId)).to.be.equal(
-            ZERO_ADDRESS
-          );
-        });
-
-        context('when account has been approved', async function () {
-          beforeEach(async function () {
-            await this.token.approve(approved, firstTokenId, { from: owner });
-          });
-
-          it('should return approved account', async function () {
-            expect(await this.token.getApproved(firstTokenId)).to.be.equal(approved);
-          });
-        });
-      });
-    });
-
-    shouldSupportInterfaces([
-      'ERC165',
-      'ERC721',
-    ]);
-  });
-}
-
-module.exports = {
-  shouldBehaveLikeERC721,
-};

test/token/ERC721/ERC721.test.js

@@ -5,82 +5,894 @@ const { ZERO_ADDRESS } = constants;
 
 const { expect } = require('chai');
 
-const { shouldBehaveLikeERC721 } = require('./ERC721.behavior');
+const { shouldSupportInterfaces } = require('../../introspection/SupportsInterface.behavior');
+
 const ERC721Mock = contract.fromArtifact('ERC721Mock');
+const ERC721ReceiverMock = contract.fromArtifact('ERC721ReceiverMock');
 
 describe('ERC721', function () {
-  const [ owner ] = accounts;
+  const [owner, newOwner, approved, anotherApproved, operator, other] = accounts;
+
+  const name = 'Non Fungible Token';
+  const symbol = 'NFT';
+
+  const firstTokenId = new BN('5042');
+  const secondTokenId = new BN('79217');
+  const nonExistentTokenId = new BN('13');
+
+  const RECEIVER_MAGIC_VALUE = '0x150b7a02';
 
   beforeEach(async function () {
-    this.token = await ERC721Mock.new();
+    this.token = await ERC721Mock.new(name, symbol);
   });
 
-  shouldBehaveLikeERC721(accounts);
+  shouldSupportInterfaces([
+    'ERC165',
+    'ERC721',
+    'ERC721Enumerable',
+    'ERC721Metadata',
+  ]);
+
+  describe('metadata', function () {
+    it('has a name', async function () {
+      expect(await this.token.name()).to.be.equal(name);
+    });
+
+    it('has a symbol', async function () {
+      expect(await this.token.symbol()).to.be.equal(symbol);
+    });
+
+    describe('token URI', function () {
+      beforeEach(async function () {
+        await this.token.mint(owner, firstTokenId);
+      });
+
+      const baseURI = 'https://api.com/v1/';
+      const sampleUri = 'mock://mytoken';
 
-  describe('internal functions', function () {
-    const tokenId = new BN('5042');
+      it('it is empty by default', async function () {
+        expect(await this.token.tokenURI(firstTokenId)).to.be.equal('');
+      });
 
-    describe('_mint(address, uint256)', function () {
-      it('reverts with a null destination address', async function () {
+      it('reverts when queried for non existent token id', async function () {
         await expectRevert(
-          this.token.mint(ZERO_ADDRESS, tokenId), 'ERC721: mint to the zero address'
+          this.token.tokenURI(nonExistentTokenId), 'ERC721Metadata: URI query for nonexistent token'
         );
       });
 
-      context('with minted token', async function () {
-        beforeEach(async function () {
-          ({ logs: this.logs } = await this.token.mint(owner, tokenId));
+      it('can be set for a token id', async function () {
+        await this.token.setTokenURI(firstTokenId, sampleUri);
+        expect(await this.token.tokenURI(firstTokenId)).to.be.equal(sampleUri);
+      });
+
+      it('reverts when setting for non existent token id', async function () {
+        await expectRevert(
+          this.token.setTokenURI(nonExistentTokenId, sampleUri), 'ERC721Metadata: URI set of nonexistent token'
+        );
+      });
+
+      it('base URI can be set', async function () {
+        await this.token.setBaseURI(baseURI);
+        expect(await this.token.baseURI()).to.equal(baseURI);
+      });
+
+      it('base URI is added as a prefix to the token URI', async function () {
+        await this.token.setBaseURI(baseURI);
+        await this.token.setTokenURI(firstTokenId, sampleUri);
+
+        expect(await this.token.tokenURI(firstTokenId)).to.be.equal(baseURI + sampleUri);
+      });
+
+      it('token URI can be changed by changing the base URI', async function () {
+        await this.token.setBaseURI(baseURI);
+        await this.token.setTokenURI(firstTokenId, sampleUri);
+
+        const newBaseURI = 'https://api.com/v2/';
+        await this.token.setBaseURI(newBaseURI);
+        expect(await this.token.tokenURI(firstTokenId)).to.be.equal(newBaseURI + sampleUri);
+      });
+
+      it('token URI is empty for tokens with no URI but with base URI', async function () {
+        await this.token.setBaseURI(baseURI);
+
+        expect(await this.token.tokenURI(firstTokenId)).to.be.equal('');
+      });
+
+      it('tokens with URI can be burnt ', async function () {
+        await this.token.setTokenURI(firstTokenId, sampleUri);
+
+        await this.token.burn(firstTokenId, { from: owner });
+
+        expect(await this.token.exists(firstTokenId)).to.equal(false);
+        await expectRevert(
+          this.token.tokenURI(firstTokenId), 'ERC721Metadata: URI query for nonexistent token'
+        );
+      });
+    });
+  });
+
+  context('with minted tokens', function () {
+    beforeEach(async function () {
+      await this.token.mint(owner, firstTokenId);
+      await this.token.mint(owner, secondTokenId);
+      this.toWhom = other; // default to other for toWhom in context-dependent tests
+    });
+
+    describe('balanceOf', function () {
+      context('when the given address owns some tokens', function () {
+        it('returns the amount of tokens owned by the given address', async function () {
+          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('2');
         });
+      });
 
-        it('emits a Transfer event', function () {
-          expectEvent.inLogs(this.logs, 'Transfer', { from: ZERO_ADDRESS, to: owner, tokenId });
+      context('when the given address does not own any tokens', function () {
+        it('returns 0', async function () {
+          expect(await this.token.balanceOf(other)).to.be.bignumber.equal('0');
         });
+      });
 
-        it('creates the token', async function () {
-          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('1');
-          expect(await this.token.ownerOf(tokenId)).to.equal(owner);
+      context('when querying the zero address', function () {
+        it('throws', async function () {
+          await expectRevert(
+            this.token.balanceOf(ZERO_ADDRESS), 'ERC721: balance query for the zero address'
+          );
         });
+      });
+    });
+
+    describe('ownerOf', function () {
+      context('when the given token ID was tracked by this token', function () {
+        const tokenId = firstTokenId;
 
-        it('reverts when adding a token id that already exists', async function () {
-          await expectRevert(this.token.mint(owner, tokenId), 'ERC721: token already minted');
+        it('returns the owner of the given token ID', async function () {
+          expect(await this.token.ownerOf(tokenId)).to.be.equal(owner);
+        });
+      });
+
+      context('when the given token ID was not tracked by this token', function () {
+        const tokenId = nonExistentTokenId;
+
+        it('reverts', async function () {
+          await expectRevert(
+            this.token.ownerOf(tokenId), 'ERC721: owner query for nonexistent token'
+          );
         });
       });
     });
 
-    describe('_burn', function () {
-      it('reverts when burning a non-existent token id', async function () {
-        await expectRevert(
-          this.token.burn(tokenId), 'ERC721: owner query for nonexistent token'
-        );
+    describe('transfers', function () {
+      const tokenId = firstTokenId;
+      const data = '0x42';
+
+      let logs = null;
+
+      beforeEach(async function () {
+        await this.token.approve(approved, tokenId, { from: owner });
+        await this.token.setApprovalForAll(operator, true, { from: owner });
       });
 
-      context('with minted token', function () {
-        beforeEach(async function () {
-          await this.token.mint(owner, tokenId);
+      const transferWasSuccessful = function ({ owner, tokenId, approved }) {
+        it('transfers the ownership of the given token ID to the given address', async function () {
+          expect(await this.token.ownerOf(tokenId)).to.be.equal(this.toWhom);
+        });
+
+        it('clears the approval for the token ID', async function () {
+          expect(await this.token.getApproved(tokenId)).to.be.equal(ZERO_ADDRESS);
         });
 
-        context('with burnt token', function () {
+        if (approved) {
+          it('emit only a transfer event', async function () {
+            expectEvent.inLogs(logs, 'Transfer', {
+              from: owner,
+              to: this.toWhom,
+              tokenId: tokenId,
+            });
+          });
+        } else {
+          it('emits only a transfer event', async function () {
+            expectEvent.inLogs(logs, 'Transfer', {
+              from: owner,
+              to: this.toWhom,
+              tokenId: tokenId,
+            });
+          });
+        }
+
+        it('adjusts owners balances', async function () {
+          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('1');
+        });
+
+        it('adjusts owners tokens by index', async function () {
+          if (!this.token.tokenOfOwnerByIndex) return;
+
+          expect(await this.token.tokenOfOwnerByIndex(this.toWhom, 0)).to.be.bignumber.equal(tokenId);
+
+          expect(await this.token.tokenOfOwnerByIndex(owner, 0)).to.be.bignumber.not.equal(tokenId);
+        });
+      };
+
+      const shouldTransferTokensByUsers = function (transferFunction) {
+        context('when called by the owner', function () {
           beforeEach(async function () {
-            ({ logs: this.logs } = await this.token.burn(tokenId));
+            ({ logs } = await transferFunction.call(this, owner, this.toWhom, tokenId, { from: owner }));
           });
+          transferWasSuccessful({ owner, tokenId, approved });
+        });
 
-          it('emits a Transfer event', function () {
-            expectEvent.inLogs(this.logs, 'Transfer', { from: owner, to: ZERO_ADDRESS, tokenId });
+        context('when called by the approved individual', function () {
+          beforeEach(async function () {
+            ({ logs } = await transferFunction.call(this, owner, this.toWhom, tokenId, { from: approved }));
           });
+          transferWasSuccessful({ owner, tokenId, approved });
+        });
 
-          it('deletes the token', async function () {
-            expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('0');
+        context('when called by the operator', function () {
+          beforeEach(async function () {
+            ({ logs } = await transferFunction.call(this, owner, this.toWhom, tokenId, { from: operator }));
+          });
+          transferWasSuccessful({ owner, tokenId, approved });
+        });
+
+        context('when called by the owner without an approved user', function () {
+          beforeEach(async function () {
+            await this.token.approve(ZERO_ADDRESS, tokenId, { from: owner });
+            ({ logs } = await transferFunction.call(this, owner, this.toWhom, tokenId, { from: operator }));
+          });
+          transferWasSuccessful({ owner, tokenId, approved: null });
+        });
+
+        context('when sent to the owner', function () {
+          beforeEach(async function () {
+            ({ logs } = await transferFunction.call(this, owner, owner, tokenId, { from: owner }));
+          });
+
+          it('keeps ownership of the token', async function () {
+            expect(await this.token.ownerOf(tokenId)).to.be.equal(owner);
+          });
+
+          it('clears the approval for the token ID', async function () {
+            expect(await this.token.getApproved(tokenId)).to.be.equal(ZERO_ADDRESS);
+          });
+
+          it('emits only a transfer event', async function () {
+            expectEvent.inLogs(logs, 'Transfer', {
+              from: owner,
+              to: owner,
+              tokenId: tokenId,
+            });
+          });
+
+          it('keeps the owner balance', async function () {
+            expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('2');
+          });
+
+          it('keeps same tokens by index', async function () {
+            if (!this.token.tokenOfOwnerByIndex) return;
+            const tokensListed = await Promise.all(
+              [0, 1].map(i => this.token.tokenOfOwnerByIndex(owner, i))
+            );
+            expect(tokensListed.map(t => t.toNumber())).to.have.members(
+              [firstTokenId.toNumber(), secondTokenId.toNumber()]
+            );
+          });
+        });
+
+        context('when the address of the previous owner is incorrect', function () {
+          it('reverts', async function () {
+            await expectRevert(
+              transferFunction.call(this, other, other, tokenId, { from: owner }),
+              'ERC721: transfer of token that is not own'
+            );
+          });
+        });
+
+        context('when the sender is not authorized for the token id', function () {
+          it('reverts', async function () {
+            await expectRevert(
+              transferFunction.call(this, owner, other, tokenId, { from: other }),
+              'ERC721: transfer caller is not owner nor approved'
+            );
+          });
+        });
+
+        context('when the given token ID does not exist', function () {
+          it('reverts', async function () {
+            await expectRevert(
+              transferFunction.call(this, owner, other, nonExistentTokenId, { from: owner }),
+              'ERC721: operator query for nonexistent token'
+            );
+          });
+        });
+
+        context('when the address to transfer the token to is the zero address', function () {
+          it('reverts', async function () {
+            await expectRevert(
+              transferFunction.call(this, owner, ZERO_ADDRESS, tokenId, { from: owner }),
+              'ERC721: transfer to the zero address'
+            );
+          });
+        });
+      };
+
+      describe('via transferFrom', function () {
+        shouldTransferTokensByUsers(function (from, to, tokenId, opts) {
+          return this.token.transferFrom(from, to, tokenId, opts);
+        });
+      });
+
+      describe('via safeTransferFrom', function () {
+        const safeTransferFromWithData = function (from, to, tokenId, opts) {
+          return this.token.methods['safeTransferFrom(address,address,uint256,bytes)'](from, to, tokenId, data, opts);
+        };
+
+        const safeTransferFromWithoutData = function (from, to, tokenId, opts) {
+          return this.token.methods['safeTransferFrom(address,address,uint256)'](from, to, tokenId, opts);
+        };
+
+        const shouldTransferSafely = function (transferFun, data) {
+          describe('to a user account', function () {
+            shouldTransferTokensByUsers(transferFun);
+          });
+
+          describe('to a valid receiver contract', function () {
+            beforeEach(async function () {
+              this.receiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, false);
+              this.toWhom = this.receiver.address;
+            });
+
+            shouldTransferTokensByUsers(transferFun);
+
+            it('should call onERC721Received', async function () {
+              const receipt = await transferFun.call(this, owner, this.receiver.address, tokenId, { from: owner });
+
+              await expectEvent.inTransaction(receipt.tx, ERC721ReceiverMock, 'Received', {
+                operator: owner,
+                from: owner,
+                tokenId: tokenId,
+                data: data,
+              });
+            });
+
+            it('should call onERC721Received from approved', async function () {
+              const receipt = await transferFun.call(this, owner, this.receiver.address, tokenId, { from: approved });
+
+              await expectEvent.inTransaction(receipt.tx, ERC721ReceiverMock, 'Received', {
+                operator: approved,
+                from: owner,
+                tokenId: tokenId,
+                data: data,
+              });
+            });
+
+            describe('with an invalid token id', function () {
+              it('reverts', async function () {
+                await expectRevert(
+                  transferFun.call(
+                    this,
+                    owner,
+                    this.receiver.address,
+                    nonExistentTokenId,
+                    { from: owner },
+                  ),
+                  'ERC721: operator query for nonexistent token'
+                );
+              });
+            });
+          });
+        };
+
+        describe('with data', function () {
+          shouldTransferSafely(safeTransferFromWithData, data);
+        });
+
+        describe('without data', function () {
+          shouldTransferSafely(safeTransferFromWithoutData, null);
+        });
+
+        describe('to a receiver contract returning unexpected value', function () {
+          it('reverts', async function () {
+            const invalidReceiver = await ERC721ReceiverMock.new('0x42', false);
             await expectRevert(
-              this.token.ownerOf(tokenId), 'ERC721: owner query for nonexistent token'
+              this.token.safeTransferFrom(owner, invalidReceiver.address, tokenId, { from: owner }),
+              'ERC721: transfer to non ERC721Receiver implementer'
             );
           });
+        });
 
-          it('reverts when burning a token id that has been deleted', async function () {
+        describe('to a receiver contract that throws', function () {
+          it('reverts', async function () {
+            const revertingReceiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, true);
             await expectRevert(
-              this.token.burn(tokenId), 'ERC721: owner query for nonexistent token'
+              this.token.safeTransferFrom(owner, revertingReceiver.address, tokenId, { from: owner }),
+              'ERC721ReceiverMock: reverting'
             );
           });
         });
+
+        describe('to a contract that does not implement the required function', function () {
+          it('reverts', async function () {
+            const nonReceiver = this.token;
+            await expectRevert(
+              this.token.safeTransferFrom(owner, nonReceiver.address, tokenId, { from: owner }),
+              'ERC721: transfer to non ERC721Receiver implementer'
+            );
+          });
+        });
+      });
+    });
+
+    describe('safe mint', function () {
+      const fourthTokenId = new BN(4);
+      const tokenId = fourthTokenId;
+      const data = '0x42';
+
+      describe('via safeMint', function () { // regular minting is tested in ERC721Mintable.test.js and others
+        it('should call onERC721Received — with data', async function () {
+          this.receiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, false);
+          const receipt = await this.token.safeMint(this.receiver.address, tokenId, data);
+
+          await expectEvent.inTransaction(receipt.tx, ERC721ReceiverMock, 'Received', {
+            from: ZERO_ADDRESS,
+            tokenId: tokenId,
+            data: data,
+          });
+        });
+
+        it('should call onERC721Received — without data', async function () {
+          this.receiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, false);
+          const receipt = await this.token.safeMint(this.receiver.address, tokenId);
+
+          await expectEvent.inTransaction(receipt.tx, ERC721ReceiverMock, 'Received', {
+            from: ZERO_ADDRESS,
+            tokenId: tokenId,
+          });
+        });
+
+        context('to a receiver contract returning unexpected value', function () {
+          it('reverts', async function () {
+            const invalidReceiver = await ERC721ReceiverMock.new('0x42', false);
+            await expectRevert(
+              this.token.safeMint(invalidReceiver.address, tokenId),
+              'ERC721: transfer to non ERC721Receiver implementer'
+            );
+          });
+        });
+
+        context('to a receiver contract that throws', function () {
+          it('reverts', async function () {
+            const revertingReceiver = await ERC721ReceiverMock.new(RECEIVER_MAGIC_VALUE, true);
+            await expectRevert(
+              this.token.safeMint(revertingReceiver.address, tokenId),
+              'ERC721ReceiverMock: reverting'
+            );
+          });
+        });
+
+        context('to a contract that does not implement the required function', function () {
+          it('reverts', async function () {
+            const nonReceiver = this.token;
+            await expectRevert(
+              this.token.safeMint(nonReceiver.address, tokenId),
+              'ERC721: transfer to non ERC721Receiver implementer'
+            );
+          });
+        });
+      });
+    });
+
+    describe('approve', function () {
+      const tokenId = firstTokenId;
+
+      let logs = null;
+
+      const itClearsApproval = function () {
+        it('clears approval for the token', async function () {
+          expect(await this.token.getApproved(tokenId)).to.be.equal(ZERO_ADDRESS);
+        });
+      };
+
+      const itApproves = function (address) {
+        it('sets the approval for the target address', async function () {
+          expect(await this.token.getApproved(tokenId)).to.be.equal(address);
+        });
+      };
+
+      const itEmitsApprovalEvent = function (address) {
+        it('emits an approval event', async function () {
+          expectEvent.inLogs(logs, 'Approval', {
+            owner: owner,
+            approved: address,
+            tokenId: tokenId,
+          });
+        });
+      };
+
+      context('when clearing approval', function () {
+        context('when there was no prior approval', function () {
+          beforeEach(async function () {
+            ({ logs } = await this.token.approve(ZERO_ADDRESS, tokenId, { from: owner }));
+          });
+
+          itClearsApproval();
+          itEmitsApprovalEvent(ZERO_ADDRESS);
+        });
+
+        context('when there was a prior approval', function () {
+          beforeEach(async function () {
+            await this.token.approve(approved, tokenId, { from: owner });
+            ({ logs } = await this.token.approve(ZERO_ADDRESS, tokenId, { from: owner }));
+          });
+
+          itClearsApproval();
+          itEmitsApprovalEvent(ZERO_ADDRESS);
+        });
+      });
+
+      context('when approving a non-zero address', function () {
+        context('when there was no prior approval', function () {
+          beforeEach(async function () {
+            ({ logs } = await this.token.approve(approved, tokenId, { from: owner }));
+          });
+
+          itApproves(approved);
+          itEmitsApprovalEvent(approved);
+        });
+
+        context('when there was a prior approval to the same address', function () {
+          beforeEach(async function () {
+            await this.token.approve(approved, tokenId, { from: owner });
+            ({ logs } = await this.token.approve(approved, tokenId, { from: owner }));
+          });
+
+          itApproves(approved);
+          itEmitsApprovalEvent(approved);
+        });
+
+        context('when there was a prior approval to a different address', function () {
+          beforeEach(async function () {
+            await this.token.approve(anotherApproved, tokenId, { from: owner });
+            ({ logs } = await this.token.approve(anotherApproved, tokenId, { from: owner }));
+          });
+
+          itApproves(anotherApproved);
+          itEmitsApprovalEvent(anotherApproved);
+        });
+      });
+
+      context('when the address that receives the approval is the owner', function () {
+        it('reverts', async function () {
+          await expectRevert(
+            this.token.approve(owner, tokenId, { from: owner }), 'ERC721: approval to current owner'
+          );
+        });
+      });
+
+      context('when the sender does not own the given token ID', function () {
+        it('reverts', async function () {
+          await expectRevert(this.token.approve(approved, tokenId, { from: other }),
+            'ERC721: approve caller is not owner nor approved');
+        });
+      });
+
+      context('when the sender is approved for the given token ID', function () {
+        it('reverts', async function () {
+          await this.token.approve(approved, tokenId, { from: owner });
+          await expectRevert(this.token.approve(anotherApproved, tokenId, { from: approved }),
+            'ERC721: approve caller is not owner nor approved for all');
+        });
+      });
+
+      context('when the sender is an operator', function () {
+        beforeEach(async function () {
+          await this.token.setApprovalForAll(operator, true, { from: owner });
+          ({ logs } = await this.token.approve(approved, tokenId, { from: operator }));
+        });
+
+        itApproves(approved);
+        itEmitsApprovalEvent(approved);
+      });
+
+      context('when the given token ID does not exist', function () {
+        it('reverts', async function () {
+          await expectRevert(this.token.approve(approved, nonExistentTokenId, { from: operator }),
+            'ERC721: owner query for nonexistent token');
+        });
+      });
+    });
+
+    describe('setApprovalForAll', function () {
+      context('when the operator willing to approve is not the owner', function () {
+        context('when there is no operator approval set by the sender', function () {
+          it('approves the operator', async function () {
+            await this.token.setApprovalForAll(operator, true, { from: owner });
+
+            expect(await this.token.isApprovedForAll(owner, operator)).to.equal(true);
+          });
+
+          it('emits an approval event', async function () {
+            const { logs } = await this.token.setApprovalForAll(operator, true, { from: owner });
+
+            expectEvent.inLogs(logs, 'ApprovalForAll', {
+              owner: owner,
+              operator: operator,
+              approved: true,
+            });
+          });
+        });
+
+        context('when the operator was set as not approved', function () {
+          beforeEach(async function () {
+            await this.token.setApprovalForAll(operator, false, { from: owner });
+          });
+
+          it('approves the operator', async function () {
+            await this.token.setApprovalForAll(operator, true, { from: owner });
+
+            expect(await this.token.isApprovedForAll(owner, operator)).to.equal(true);
+          });
+
+          it('emits an approval event', async function () {
+            const { logs } = await this.token.setApprovalForAll(operator, true, { from: owner });
+
+            expectEvent.inLogs(logs, 'ApprovalForAll', {
+              owner: owner,
+              operator: operator,
+              approved: true,
+            });
+          });
+
+          it('can unset the operator approval', async function () {
+            await this.token.setApprovalForAll(operator, false, { from: owner });
+
+            expect(await this.token.isApprovedForAll(owner, operator)).to.equal(false);
+          });
+        });
+
+        context('when the operator was already approved', function () {
+          beforeEach(async function () {
+            await this.token.setApprovalForAll(operator, true, { from: owner });
+          });
+
+          it('keeps the approval to the given address', async function () {
+            await this.token.setApprovalForAll(operator, true, { from: owner });
+
+            expect(await this.token.isApprovedForAll(owner, operator)).to.equal(true);
+          });
+
+          it('emits an approval event', async function () {
+            const { logs } = await this.token.setApprovalForAll(operator, true, { from: owner });
+
+            expectEvent.inLogs(logs, 'ApprovalForAll', {
+              owner: owner,
+              operator: operator,
+              approved: true,
+            });
+          });
+        });
+      });
+
+      context('when the operator is the owner', function () {
+        it('reverts', async function () {
+          await expectRevert(this.token.setApprovalForAll(owner, true, { from: owner }),
+            'ERC721: approve to caller');
+        });
+      });
+    });
+
+    describe('getApproved', async function () {
+      context('when token is not minted', async function () {
+        it('reverts', async function () {
+          await expectRevert(
+            this.token.getApproved(nonExistentTokenId),
+            'ERC721: approved query for nonexistent token'
+          );
+        });
+      });
+
+      context('when token has been minted ', async function () {
+        it('should return the zero address', async function () {
+          expect(await this.token.getApproved(firstTokenId)).to.be.equal(
+            ZERO_ADDRESS
+          );
+        });
+
+        context('when account has been approved', async function () {
+          beforeEach(async function () {
+            await this.token.approve(approved, firstTokenId, { from: owner });
+          });
+
+          it('should return approved account', async function () {
+            expect(await this.token.getApproved(firstTokenId)).to.be.equal(approved);
+          });
+        });
+      });
+    });
+
+    describe('tokensOfOwner', function () {
+      it('returns total tokens of owner', async function () {
+        const tokenIds = await this.token.tokensOfOwner(owner);
+        expect(tokenIds.length).to.equal(2);
+        expect(tokenIds[0]).to.be.bignumber.equal(firstTokenId);
+        expect(tokenIds[1]).to.be.bignumber.equal(secondTokenId);
+      });
+    });
+
+    describe('totalSupply', function () {
+      it('returns total token supply', async function () {
+        expect(await this.token.totalSupply()).to.be.bignumber.equal('2');
+      });
+    });
+
+    describe('tokenOfOwnerByIndex', function () {
+      describe('when the given index is lower than the amount of tokens owned by the given address', function () {
+        it('returns the token ID placed at the given index', async function () {
+          expect(await this.token.tokenOfOwnerByIndex(owner, 0)).to.be.bignumber.equal(firstTokenId);
+        });
+      });
+
+      describe('when the index is greater than or equal to the total tokens owned by the given address', function () {
+        it('reverts', async function () {
+          await expectRevert(
+            this.token.tokenOfOwnerByIndex(owner, 2), 'ERC721Enumerable: owner index out of bounds'
+          );
+        });
+      });
+
+      describe('when the given address does not own any token', function () {
+        it('reverts', async function () {
+          await expectRevert(
+            this.token.tokenOfOwnerByIndex(other, 0), 'ERC721Enumerable: owner index out of bounds'
+          );
+        });
+      });
+
+      describe('after transferring all tokens to another user', function () {
+        beforeEach(async function () {
+          await this.token.transferFrom(owner, other, firstTokenId, { from: owner });
+          await this.token.transferFrom(owner, other, secondTokenId, { from: owner });
+        });
+
+        it('returns correct token IDs for target', async function () {
+          expect(await this.token.balanceOf(other)).to.be.bignumber.equal('2');
+          const tokensListed = await Promise.all(
+            [0, 1].map(i => this.token.tokenOfOwnerByIndex(other, i))
+          );
+          expect(tokensListed.map(t => t.toNumber())).to.have.members([firstTokenId.toNumber(),
+            secondTokenId.toNumber()]);
+        });
+
+        it('returns empty collection for original owner', async function () {
+          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('0');
+          await expectRevert(
+            this.token.tokenOfOwnerByIndex(owner, 0), 'ERC721Enumerable: owner index out of bounds'
+          );
+        });
+      });
+    });
+
+    describe('tokenByIndex', function () {
+      it('should return all tokens', async function () {
+        const tokensListed = await Promise.all(
+          [0, 1].map(i => this.token.tokenByIndex(i))
+        );
+        expect(tokensListed.map(t => t.toNumber())).to.have.members([firstTokenId.toNumber(),
+          secondTokenId.toNumber()]);
+      });
+
+      it('should revert if index is greater than supply', async function () {
+        await expectRevert(
+          this.token.tokenByIndex(2), 'ERC721Enumerable: global index out of bounds'
+        );
+      });
+
+      [firstTokenId, secondTokenId].forEach(function (tokenId) {
+        it(`should return all tokens after burning token ${tokenId} and minting new tokens`, async function () {
+          const newTokenId = new BN(300);
+          const anotherNewTokenId = new BN(400);
+
+          await this.token.burn(tokenId, { from: owner });
+          await this.token.mint(newOwner, newTokenId);
+          await this.token.mint(newOwner, anotherNewTokenId);
+
+          expect(await this.token.totalSupply()).to.be.bignumber.equal('3');
+
+          const tokensListed = await Promise.all(
+            [0, 1, 2].map(i => this.token.tokenByIndex(i))
+          );
+          const expectedTokens = [firstTokenId, secondTokenId, newTokenId, anotherNewTokenId].filter(
+            x => (x !== tokenId)
+          );
+          expect(tokensListed.map(t => t.toNumber())).to.have.members(expectedTokens.map(t => t.toNumber()));
+        });
+      });
+    });
+  });
+
+  describe('_mint(address, uint256)', function () {
+    it('reverts with a null destination address', async function () {
+      await expectRevert(
+        this.token.mint(ZERO_ADDRESS, firstTokenId), 'ERC721: mint to the zero address'
+      );
+    });
+
+    context('with minted token', async function () {
+      beforeEach(async function () {
+        ({ logs: this.logs } = await this.token.mint(owner, firstTokenId));
+      });
+
+      it('emits a Transfer event', function () {
+        expectEvent.inLogs(this.logs, 'Transfer', { from: ZERO_ADDRESS, to: owner, tokenId: firstTokenId });
+      });
+
+      it('creates the token', async function () {
+        expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('1');
+        expect(await this.token.ownerOf(firstTokenId)).to.equal(owner);
+      });
+
+      it('adjusts owner tokens by index', async function () {
+        expect(await this.token.tokenOfOwnerByIndex(owner, 0)).to.be.bignumber.equal(firstTokenId);
+      });
+
+      it('adjusts all tokens list', async function () {
+        expect(await this.token.tokenByIndex(0)).to.be.bignumber.equal(firstTokenId);
+      });
+
+      it('reverts when adding a token id that already exists', async function () {
+        await expectRevert(this.token.mint(owner, firstTokenId), 'ERC721: token already minted');
+      });
+    });
+  });
+
+  describe('_burn', function () {
+    it('reverts when burning a non-existent token id', async function () {
+      await expectRevert(
+        this.token.burn(firstTokenId), 'ERC721: owner query for nonexistent token'
+      );
+    });
+
+    context('with minted tokens', function () {
+      beforeEach(async function () {
+        await this.token.mint(owner, firstTokenId);
+        await this.token.mint(owner, secondTokenId);
+      });
+
+      context('with burnt token', function () {
+        beforeEach(async function () {
+          ({ logs: this.logs } = await this.token.burn(firstTokenId));
+        });
+
+        it('emits a Transfer event', function () {
+          expectEvent.inLogs(this.logs, 'Transfer', { from: owner, to: ZERO_ADDRESS, tokenId: firstTokenId });
+        });
+
+        it('deletes the token', async function () {
+          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('1');
+          await expectRevert(
+            this.token.ownerOf(firstTokenId), 'ERC721: owner query for nonexistent token'
+          );
+        });
+
+        it('removes that token from the token list of the owner', async function () {
+          expect(await this.token.tokenOfOwnerByIndex(owner, 0)).to.be.bignumber.equal(secondTokenId);
+        });
+
+        it('adjusts all tokens list', async function () {
+          expect(await this.token.tokenByIndex(0)).to.be.bignumber.equal(secondTokenId);
+        });
+
+        it('burns all tokens', async function () {
+          await this.token.burn(secondTokenId, { from: owner });
+          expect(await this.token.totalSupply()).to.be.bignumber.equal('0');
+          await expectRevert(
+            this.token.tokenByIndex(0), 'ERC721Enumerable: global index out of bounds'
+          );
+        });
+
+        it('reverts when burning a token id that has been deleted', async function () {
+          await expectRevert(
+            this.token.burn(firstTokenId), 'ERC721: owner query for nonexistent token'
+          );
+        });
       });
     });
   });

test/token/ERC721/ERC721Burnable.test.js

@@ -14,8 +14,11 @@ describe('ERC721Burnable', function () {
   const secondTokenId = new BN(2);
   const unknownTokenId = new BN(3);
 
+  const name = 'Non Fungible Token';
+  const symbol = 'NFT';
+
   beforeEach(async function () {
-    this.token = await ERC721BurnableMock.new();
+    this.token = await ERC721BurnableMock.new(name, symbol);
   });
 
   describe('like a burnable ERC721', function () {

test/token/ERC721/ERC721Full.test.js

@@ -1,249 +0,0 @@
-const { accounts, contract } = require('@openzeppelin/test-environment');
-
-const { BN, expectRevert } = require('@openzeppelin/test-helpers');
-const { expect } = require('chai');
-
-const { shouldBehaveLikeERC721 } = require('./ERC721.behavior');
-const { shouldSupportInterfaces } = require('../../introspection/SupportsInterface.behavior');
-
-const ERC721FullMock = contract.fromArtifact('ERC721FullMock');
-
-describe('ERC721Full', function () {
-  const [owner, newOwner, other ] = accounts;
-
-  const name = 'Non Fungible Token';
-  const symbol = 'NFT';
-  const firstTokenId = new BN(100);
-  const secondTokenId = new BN(200);
-  const thirdTokenId = new BN(300);
-  const nonExistentTokenId = new BN(999);
-
-  beforeEach(async function () {
-    this.token = await ERC721FullMock.new(name, symbol);
-  });
-
-  describe('like a full ERC721', function () {
-    beforeEach(async function () {
-      await this.token.mint(owner, firstTokenId);
-      await this.token.mint(owner, secondTokenId);
-    });
-
-    describe('mint', function () {
-      beforeEach(async function () {
-        await this.token.mint(newOwner, thirdTokenId);
-      });
-
-      it('adjusts owner tokens by index', async function () {
-        expect(await this.token.tokenOfOwnerByIndex(newOwner, 0)).to.be.bignumber.equal(thirdTokenId);
-      });
-
-      it('adjusts all tokens list', async function () {
-        expect(await this.token.tokenByIndex(2)).to.be.bignumber.equal(thirdTokenId);
-      });
-    });
-
-    describe('burn', function () {
-      beforeEach(async function () {
-        await this.token.burn(firstTokenId, { from: owner });
-      });
-
-      it('removes that token from the token list of the owner', async function () {
-        expect(await this.token.tokenOfOwnerByIndex(owner, 0)).to.be.bignumber.equal(secondTokenId);
-      });
-
-      it('adjusts all tokens list', async function () {
-        expect(await this.token.tokenByIndex(0)).to.be.bignumber.equal(secondTokenId);
-      });
-
-      it('burns all tokens', async function () {
-        await this.token.burn(secondTokenId, { from: owner });
-        expect(await this.token.totalSupply()).to.be.bignumber.equal('0');
-        await expectRevert(
-          this.token.tokenByIndex(0), 'ERC721Enumerable: global index out of bounds'
-        );
-      });
-    });
-
-    describe('metadata', function () {
-      it('has a name', async function () {
-        expect(await this.token.name()).to.be.equal(name);
-      });
-
-      it('has a symbol', async function () {
-        expect(await this.token.symbol()).to.be.equal(symbol);
-      });
-
-      describe('token URI', function () {
-        const baseURI = 'https://api.com/v1/';
-        const sampleUri = 'mock://mytoken';
-
-        it('it is empty by default', async function () {
-          expect(await this.token.tokenURI(firstTokenId)).to.be.equal('');
-        });
-
-        it('reverts when queried for non existent token id', async function () {
-          await expectRevert(
-            this.token.tokenURI(nonExistentTokenId), 'ERC721Metadata: URI query for nonexistent token'
-          );
-        });
-
-        it('can be set for a token id', async function () {
-          await this.token.setTokenURI(firstTokenId, sampleUri);
-          expect(await this.token.tokenURI(firstTokenId)).to.be.equal(sampleUri);
-        });
-
-        it('reverts when setting for non existent token id', async function () {
-          await expectRevert(
-            this.token.setTokenURI(nonExistentTokenId, sampleUri), 'ERC721Metadata: URI set of nonexistent token'
-          );
-        });
-
-        it('base URI can be set', async function () {
-          await this.token.setBaseURI(baseURI);
-          expect(await this.token.baseURI()).to.equal(baseURI);
-        });
-
-        it('base URI is added as a prefix to the token URI', async function () {
-          await this.token.setBaseURI(baseURI);
-          await this.token.setTokenURI(firstTokenId, sampleUri);
-
-          expect(await this.token.tokenURI(firstTokenId)).to.be.equal(baseURI + sampleUri);
-        });
-
-        it('token URI can be changed by changing the base URI', async function () {
-          await this.token.setBaseURI(baseURI);
-          await this.token.setTokenURI(firstTokenId, sampleUri);
-
-          const newBaseURI = 'https://api.com/v2/';
-          await this.token.setBaseURI(newBaseURI);
-          expect(await this.token.tokenURI(firstTokenId)).to.be.equal(newBaseURI + sampleUri);
-        });
-
-        it('token URI is empty for tokens with no URI but with base URI', async function () {
-          await this.token.setBaseURI(baseURI);
-
-          expect(await this.token.tokenURI(firstTokenId)).to.be.equal('');
-        });
-
-        it('tokens with URI can be burnt ', async function () {
-          await this.token.setTokenURI(firstTokenId, sampleUri);
-
-          await this.token.burn(firstTokenId, { from: owner });
-
-          expect(await this.token.exists(firstTokenId)).to.equal(false);
-          await expectRevert(
-            this.token.tokenURI(firstTokenId), 'ERC721Metadata: URI query for nonexistent token'
-          );
-        });
-      });
-    });
-
-    describe('tokensOfOwner', function () {
-      it('returns total tokens of owner', async function () {
-        const tokenIds = await this.token.tokensOfOwner(owner);
-        expect(tokenIds.length).to.equal(2);
-        expect(tokenIds[0]).to.be.bignumber.equal(firstTokenId);
-        expect(tokenIds[1]).to.be.bignumber.equal(secondTokenId);
-      });
-    });
-
-    describe('totalSupply', function () {
-      it('returns total token supply', async function () {
-        expect(await this.token.totalSupply()).to.be.bignumber.equal('2');
-      });
-    });
-
-    describe('tokenOfOwnerByIndex', function () {
-      describe('when the given index is lower than the amount of tokens owned by the given address', function () {
-        it('returns the token ID placed at the given index', async function () {
-          expect(await this.token.tokenOfOwnerByIndex(owner, 0)).to.be.bignumber.equal(firstTokenId);
-        });
-      });
-
-      describe('when the index is greater than or equal to the total tokens owned by the given address', function () {
-        it('reverts', async function () {
-          await expectRevert(
-            this.token.tokenOfOwnerByIndex(owner, 2), 'ERC721Enumerable: owner index out of bounds'
-          );
-        });
-      });
-
-      describe('when the given address does not own any token', function () {
-        it('reverts', async function () {
-          await expectRevert(
-            this.token.tokenOfOwnerByIndex(other, 0), 'ERC721Enumerable: owner index out of bounds'
-          );
-        });
-      });
-
-      describe('after transferring all tokens to another user', function () {
-        beforeEach(async function () {
-          await this.token.transferFrom(owner, other, firstTokenId, { from: owner });
-          await this.token.transferFrom(owner, other, secondTokenId, { from: owner });
-        });
-
-        it('returns correct token IDs for target', async function () {
-          expect(await this.token.balanceOf(other)).to.be.bignumber.equal('2');
-          const tokensListed = await Promise.all(
-            [0, 1].map(i => this.token.tokenOfOwnerByIndex(other, i))
-          );
-          expect(tokensListed.map(t => t.toNumber())).to.have.members([firstTokenId.toNumber(),
-            secondTokenId.toNumber()]);
-        });
-
-        it('returns empty collection for original owner', async function () {
-          expect(await this.token.balanceOf(owner)).to.be.bignumber.equal('0');
-          await expectRevert(
-            this.token.tokenOfOwnerByIndex(owner, 0), 'ERC721Enumerable: owner index out of bounds'
-          );
-        });
-      });
-    });
-
-    describe('tokenByIndex', function () {
-      it('should return all tokens', async function () {
-        const tokensListed = await Promise.all(
-          [0, 1].map(i => this.token.tokenByIndex(i))
-        );
-        expect(tokensListed.map(t => t.toNumber())).to.have.members([firstTokenId.toNumber(),
-          secondTokenId.toNumber()]);
-      });
-
-      it('should revert if index is greater than supply', async function () {
-        await expectRevert(
-          this.token.tokenByIndex(2), 'ERC721Enumerable: global index out of bounds'
-        );
-      });
-
-      [firstTokenId, secondTokenId].forEach(function (tokenId) {
-        it(`should return all tokens after burning token ${tokenId} and minting new tokens`, async function () {
-          const newTokenId = new BN(300);
-          const anotherNewTokenId = new BN(400);
-
-          await this.token.burn(tokenId, { from: owner });
-          await this.token.mint(newOwner, newTokenId);
-          await this.token.mint(newOwner, anotherNewTokenId);
-
-          expect(await this.token.totalSupply()).to.be.bignumber.equal('3');
-
-          const tokensListed = await Promise.all(
-            [0, 1, 2].map(i => this.token.tokenByIndex(i))
-          );
-          const expectedTokens = [firstTokenId, secondTokenId, newTokenId, anotherNewTokenId].filter(
-            x => (x !== tokenId)
-          );
-          expect(tokensListed.map(t => t.toNumber())).to.have.members(expectedTokens.map(t => t.toNumber()));
-        });
-      });
-    });
-  });
-
-  shouldBehaveLikeERC721(accounts);
-
-  shouldSupportInterfaces([
-    'ERC165',
-    'ERC721',
-    'ERC721Enumerable',
-    'ERC721Metadata',
-  ]);
-});

test/token/ERC721/ERC721Holder.test.js

@@ -10,8 +10,11 @@ const ERC721Mock = contract.fromArtifact('ERC721Mock');
 describe('ERC721Holder', function () {
   const [ owner ] = accounts;
 
+  const name = 'Non Fungible Token';
+  const symbol = 'NFT';
+
   it('receives an ERC721 token', async function () {
-    const token = await ERC721Mock.new();
+    const token = await ERC721Mock.new(name, symbol);
     const tokenId = new BN(1);
     await token.mint(owner, tokenId);
 

test/token/ERC721/ERC721Pausable.test.js

@@ -5,19 +5,16 @@ const { ZERO_ADDRESS } = constants;
 
 const { expect } = require('chai');
 
-const { shouldBehaveLikeERC721 } = require('./ERC721.behavior');
-
 const ERC721PausableMock = contract.fromArtifact('ERC721PausableMock');
 
 describe('ERC721Pausable', function () {
   const [ owner, receiver, operator ] = accounts;
 
-  beforeEach(async function () {
-    this.token = await ERC721PausableMock.new();
-  });
+  const name = 'Non Fungible Token';
+  const symbol = 'NFT';
 
-  context('when token is not paused yet', function () {
-    shouldBehaveLikeERC721(accounts);
+  beforeEach(async function () {
+    this.token = await ERC721PausableMock.new(name, symbol);
   });
 
   context('when token is paused', function () {