Update ERC721 to latest 1.11.0 from OpenZeppelin-solidity (#11)

* Update ERC721 to latest 1.11.0 from OpenZeppelin-solidity

* Hardcode supported interfaces instead of using lookup table. This avoids shifting storage when extending supports interface.

* Update build artifacts

* Fix linter errors

build/contracts/AddressUtils.json

@@ -507,5 +507,5 @@
   },
   "networks": {},
   "schemaVersion": "2.0.0",
-  "updatedAt": "2018-08-23T17:26:04.150Z"
+  "updatedAt": "2018-08-27T20:45:00.202Z"
 }
\ No newline at end of file

build/contracts/ECRecovery.json

 {
   "contractName": "ECRecovery",
   "abi": [],
-  "bytecode": "0x604c602c600b82828239805160001a60731460008114601c57601e565bfe5b5030600052607381538281f30073000000000000000000000000000000000000000030146080604052600080fd00a165627a7a7230582095f4276bbe910450a81a9f24c9666db9e203894c52a3fdbade54b3b5738e695e0029",
-  "deployedBytecode": "0x73000000000000000000000000000000000000000030146080604052600080fd00a165627a7a7230582095f4276bbe910450a81a9f24c9666db9e203894c52a3fdbade54b3b5738e695e0029",
+  "bytecode": "0x604c602c600b82828239805160001a60731460008114601c57601e565bfe5b5030600052607381538281f30073000000000000000000000000000000000000000030146080604052600080fd00a165627a7a723058205b790ca6c853c7e32fb7ac75e4760a40d639601e5e2dcf7ace2abff11907a7450029",
+  "deployedBytecode": "0x73000000000000000000000000000000000000000030146080604052600080fd00a165627a7a723058205b790ca6c853c7e32fb7ac75e4760a40d639601e5e2dcf7ace2abff11907a7450029",
   "sourceMap": "309:1640:1:-;;132:2:-1;166:7;155:9;146:7;137:37;252:7;246:14;243:1;238:23;232:4;229:33;270:1;265:20;;;;222:63;;265:20;274:9;222:63;;298:9;295:1;288:20;328:4;319:7;311:22;352:7;343;336:24",
   "deployedSourceMap": "309:1640:1:-;;;;;;;;",
   "source": "pragma solidity ^0.4.21;\n\n\n/**\n * @title Eliptic curve signature operations\n *\n * @dev Based on https://gist.github.com/axic/5b33912c6f61ae6fd96d6c4a47afde6d\n *\n * TODO Remove this library once solidity supports passing a signature to ecrecover.\n * See https://github.com/ethereum/solidity/issues/864\n *\n */\n\nlibrary ECRecovery {\n\n  /**\n   * @dev Recover signer address from a message by using their signature\n   * @param hash bytes32 message, the hash is the signed message. What is recovered is the signer address.\n   * @param sig bytes signature, the signature is generated using web3.eth.sign()\n   */\n  function recover(bytes32 hash, bytes sig)\n    internal\n    pure\n    returns (address)\n  {\n    bytes32 r;\n    bytes32 s;\n    uint8 v;\n\n    // Check the signature length\n    if (sig.length != 65) {\n      return (address(0));\n    }\n\n    // Divide the signature in r, s and v variables\n    // ecrecover takes the signature parameters, and the only way to get them\n    // currently is to use assembly.\n    // solium-disable-next-line security/no-inline-assembly\n    assembly {\n      r := mload(add(sig, 32))\n      s := mload(add(sig, 64))\n      v := byte(0, mload(add(sig, 96)))\n    }\n\n    // Version of signature should be 27 or 28, but 0 and 1 are also possible versions\n    if (v < 27) {\n      v += 27;\n    }\n\n    // If the version is correct return the signer address\n    if (v != 27 && v != 28) {\n      return (address(0));\n    } else {\n      // solium-disable-next-line arg-overflow\n      return ecrecover(hash, v, r, s);\n    }\n  }\n\n  /**\n   * toEthSignedMessageHash\n   * @dev prefix a bytes32 value with \"\\x19Ethereum Signed Message:\"\n   * @dev and hash the result\n   */\n  function toEthSignedMessageHash(bytes32 hash)\n    internal\n    pure\n    returns (bytes32)\n  {\n    // 32 is the length in bytes of hash,\n    // enforced by the type signature above\n    return keccak256(\n      \"\\x19Ethereum Signed Message:\\n32\",\n      hash\n    );\n  }\n}\n",
@@ -691,7 +691,7 @@
                             "name": "ecrecover",
                             "nodeType": "Identifier",
                             "overloadedDeclarations": [],
-                            "referencedDeclaration": 4776,
+                            "referencedDeclaration": 4871,
                             "src": "1504:9:1",
                             "typeDescriptions": {
                               "typeIdentifier": "t_function_ecrecover_pure$_t_bytes32_$_t_uint8_$_t_bytes32_$_t_bytes32_$returns$_t_address_$",
@@ -975,7 +975,7 @@
                       "name": "keccak256",
                       "nodeType": "Identifier",
                       "overloadedDeclarations": [],
-                      "referencedDeclaration": 4778,
+                      "referencedDeclaration": 4873,
                       "src": "1873:9:1",
                       "typeDescriptions": {
                         "typeIdentifier": "t_function_sha3_pure$__$returns$_t_bytes32_$",
@@ -1775,7 +1775,7 @@
                             "name": "ecrecover",
                             "nodeType": "Identifier",
                             "overloadedDeclarations": [],
-                            "referencedDeclaration": 4776,
+                            "referencedDeclaration": 4871,
                             "src": "1504:9:1",
                             "typeDescriptions": {
                               "typeIdentifier": "t_function_ecrecover_pure$_t_bytes32_$_t_uint8_$_t_bytes32_$_t_bytes32_$returns$_t_address_$",
@@ -2059,7 +2059,7 @@
                       "name": "keccak256",
                       "nodeType": "Identifier",
                       "overloadedDeclarations": [],
-                      "referencedDeclaration": 4778,
+                      "referencedDeclaration": 4873,
                       "src": "1873:9:1",
                       "typeDescriptions": {
                         "typeIdentifier": "t_function_sha3_pure$__$returns$_t_bytes32_$",
@@ -2177,9 +2177,9 @@
   },
   "compiler": {
     "name": "solc",
-    "version": "0.4.24+commit.e67f0147.Emscripten.clang"
+    "version": "0.4.23+commit.124ca40d.Emscripten.clang"
   },
   "networks": {},
-  "schemaVersion": "2.0.1",
-  "updatedAt": "2018-08-23T14:35:50.612Z"
+  "schemaVersion": "2.0.0",
+  "updatedAt": "2018-08-27T20:45:00.202Z"
 }
\ No newline at end of file

build/contracts/MerkleProof.json

 {
   "contractName": "MerkleProof",
   "abi": [],
-  "bytecode": "0x604c602c600b82828239805160001a60731460008114601c57601e565bfe5b5030600052607381538281f30073000000000000000000000000000000000000000030146080604052600080fd00a165627a7a72305820ccc41da397538bcd62e42f28e2999ceae0d28d7b83d6c3bfbda80241383dc2fc0029",
-  "deployedBytecode": "0x73000000000000000000000000000000000000000030146080604052600080fd00a165627a7a72305820ccc41da397538bcd62e42f28e2999ceae0d28d7b83d6c3bfbda80241383dc2fc0029",
+  "bytecode": "0x604c602c600b82828239805160001a60731460008114601c57601e565bfe5b5030600052607381538281f30073000000000000000000000000000000000000000030146080604052600080fd00a165627a7a72305820de3b6f14f81089bc425ad158bc3ccc2cf37c3fb8768224f30fc867a34dbc88ef0029",
+  "deployedBytecode": "0x73000000000000000000000000000000000000000030146080604052600080fd00a165627a7a72305820de3b6f14f81089bc425ad158bc3ccc2cf37c3fb8768224f30fc867a34dbc88ef0029",
   "sourceMap": "189:1052:2:-;;132:2:-1;166:7;155:9;146:7;137:37;252:7;246:14;243:1;238:23;232:4;229:33;270:1;265:20;;;;222:63;;265:20;274:9;222:63;;298:9;295:1;288:20;328:4;319:7;311:22;352:7;343;336:24",
   "deployedSourceMap": "189:1052:2:-;;;;;;;;",
   "source": "pragma solidity ^0.4.21;\n\n\n/*\n * @title MerkleProof\n * @dev Merkle proof verification\n * @note Based on https://github.com/ameensol/merkle-tree-solidity/blob/master/src/MerkleProof.sol\n */\nlibrary MerkleProof {\n  /*\n   * @dev Verifies a Merkle proof proving the existence of a leaf in a Merkle tree. Assumes that each pair of leaves\n   * and each pair of pre-images is sorted.\n   * @param _proof Merkle proof containing sibling hashes on the branch from the leaf to the root of the Merkle tree\n   * @param _root Merkle root\n   * @param _leaf Leaf of Merkle tree\n   */\n  function verifyProof(bytes32[] _proof, bytes32 _root, bytes32 _leaf) internal pure returns (bool) {\n    bytes32 computedHash = _leaf;\n\n    for (uint256 i = 0; i < _proof.length; i++) {\n      bytes32 proofElement = _proof[i];\n\n      if (computedHash < proofElement) {\n        // Hash(current computed hash + current element of the proof)\n        computedHash = keccak256(computedHash, proofElement);\n      } else {\n        // Hash(current element of the proof + current computed hash)\n        computedHash = keccak256(proofElement, computedHash);\n      }\n    }\n\n    // Check if the computed hash (root) is equal to the provided root\n    return computedHash == _root;\n  }\n}\n",
@@ -297,7 +297,7 @@
                                     "name": "keccak256",
                                     "nodeType": "Identifier",
                                     "overloadedDeclarations": [],
-                                    "referencedDeclaration": 4778,
+                                    "referencedDeclaration": 4873,
                                     "src": "1077:9:2",
                                     "typeDescriptions": {
                                       "typeIdentifier": "t_function_sha3_pure$__$returns$_t_bytes32_$",
@@ -406,7 +406,7 @@
                                     "name": "keccak256",
                                     "nodeType": "Identifier",
                                     "overloadedDeclarations": [],
-                                    "referencedDeclaration": 4778,
+                                    "referencedDeclaration": 4873,
                                     "src": "930:9:2",
                                     "typeDescriptions": {
                                       "typeIdentifier": "t_function_sha3_pure$__$returns$_t_bytes32_$",
@@ -1088,7 +1088,7 @@
                                     "name": "keccak256",
                                     "nodeType": "Identifier",
                                     "overloadedDeclarations": [],
-                                    "referencedDeclaration": 4778,
+                                    "referencedDeclaration": 4873,
                                     "src": "1077:9:2",
                                     "typeDescriptions": {
                                       "typeIdentifier": "t_function_sha3_pure$__$returns$_t_bytes32_$",
@@ -1197,7 +1197,7 @@
                                     "name": "keccak256",
                                     "nodeType": "Identifier",
                                     "overloadedDeclarations": [],
-                                    "referencedDeclaration": 4778,
+                                    "referencedDeclaration": 4873,
                                     "src": "930:9:2",
                                     "typeDescriptions": {
                                       "typeIdentifier": "t_function_sha3_pure$__$returns$_t_bytes32_$",
@@ -1591,9 +1591,9 @@
   },
   "compiler": {
     "name": "solc",
-    "version": "0.4.24+commit.e67f0147.Emscripten.clang"
+    "version": "0.4.23+commit.124ca40d.Emscripten.clang"
   },
   "networks": {},
-  "schemaVersion": "2.0.1",
-  "updatedAt": "2018-08-23T14:35:50.612Z"
+  "schemaVersion": "2.0.0",
+  "updatedAt": "2018-08-27T20:45:00.202Z"
 }
\ No newline at end of file

contracts/introspection/ERC165.sol

+pragma solidity ^0.4.21;
+
+
+/**
+ * @title ERC165
+ * @dev https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
+ */
+interface ERC165 {
+
+  /**
+   * @notice Query if a contract implements an interface
+   * @param _interfaceId The interface identifier, as specified in ERC-165
+   * @dev Interface identification is specified in ERC-165. This function
+   * uses less than 30,000 gas.
+   */
+  function supportsInterface(bytes4 _interfaceId)
+    external
+    view
+    returns (bool);
+}

contracts/introspection/ERC165Support.sol

+pragma solidity ^0.4.21;
+
+import "./ERC165.sol";
+
+/**
+ * @title ERC165Support
+ * @dev Implements ERC165 returning true for ERC165 interface identifier
+ */
+contract ERC165Support is ERC165 {
+
+  bytes4 internal constant InterfaceId_ERC165 = 0x01ffc9a7;
+  /**
+   * 0x01ffc9a7 ===
+   *   bytes4(keccak256('supportsInterface(bytes4)'))
+   */
+
+  function supportsInterface(bytes4 _interfaceId)
+    external
+    view
+    returns (bool) 
+  {
+    return _supportsInterface(_interfaceId);
+  }
+
+  function _supportsInterface(bytes4 _interfaceId)
+    internal
+    view
+    returns (bool) 
+  {
+    return _interfaceId == InterfaceId_ERC165;
+  }
+}

contracts/mocks/ERC721ReceiverMock.sol

@@ -7,15 +7,22 @@ contract ERC721ReceiverMock is ERC721Receiver {
   bytes4 retval;
   bool reverts;
 
-  event Received(address _address, uint256 _tokenId, bytes _data, uint256 _gas);
+  event Received(
+    address _operator,
+    address _from,
+    uint256 _tokenId,
+    bytes _data,
+    uint256 _gas
+  );
 
-  function ERC721ReceiverMock(bytes4 _retval, bool _reverts) public {
+  constructor(bytes4 _retval, bool _reverts) public {
     retval = _retval;
     reverts = _reverts;
   }
 
   function onERC721Received(
-    address _address,
+    address _operator,
+    address _from,
     uint256 _tokenId,
     bytes _data
   )
@@ -24,7 +31,8 @@ contract ERC721ReceiverMock is ERC721Receiver {
   {
     require(!reverts);
     emit Received(
-      _address,
+      _operator,
+      _from,
       _tokenId,
       _data,
       gasleft() // msg.gas was deprecated in solidityv0.4.21

contracts/mocks/ERC721TokenMock.sol

@@ -9,7 +9,7 @@ import "../token/ERC721/ERC721Token.sol";
  * and a public setter for metadata URI
  */
 contract ERC721TokenMock is ERC721Token {
-  function ERC721TokenMock(string name, string symbol) public {
+  constructor(string name, string symbol) public {
     ERC721Token.initialize(name, symbol);
   }
 

contracts/token/ERC721/ERC721.sol

@@ -9,7 +9,14 @@ import "./ERC721Basic.sol";
  */
 contract ERC721Enumerable is ERC721Basic {
   function totalSupply() public view returns (uint256);
-  function tokenOfOwnerByIndex(address _owner, uint256 _index) public view returns (uint256 _tokenId);
+  function tokenOfOwnerByIndex(
+    address _owner,
+    uint256 _index
+  )
+    public
+    view
+    returns (uint256 _tokenId);
+
   function tokenByIndex(uint256 _index) public view returns (uint256);
 }
 
@@ -19,8 +26,8 @@ contract ERC721Enumerable is ERC721Basic {
  * @dev See https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
  */
 contract ERC721Metadata is ERC721Basic {
-  function name() public view returns (string _name);
-  function symbol() public view returns (string _symbol);
+  function name() external view returns (string _name);
+  function symbol() external view returns (string _symbol);
   function tokenURI(uint256 _tokenId) public view returns (string);
 }
 

contracts/token/ERC721/ERC721Basic.sol

 pragma solidity ^0.4.21;
 
+import "../../introspection/ERC165.sol";
+
 
 /**
  * @title ERC721 Non-Fungible Token Standard basic interface
  * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
  */
-contract ERC721Basic {
-  event Transfer(address indexed _from, address indexed _to, uint256 indexed _tokenId);
-  event Approval(address indexed _owner, address indexed _approved, uint256 indexed _tokenId);
-  event ApprovalForAll(address indexed _owner, address indexed _operator, bool _approved);
+contract ERC721Basic is ERC165 {
+  event Transfer(
+    address indexed _from,
+    address indexed _to,
+    uint256 indexed _tokenId
+  );
+  event Approval(
+    address indexed _owner,
+    address indexed _approved,
+    uint256 indexed _tokenId
+  );
+  event ApprovalForAll(
+    address indexed _owner,
+    address indexed _operator,
+    bool _approved
+  );
 
   function balanceOf(address _owner) public view returns (uint256 _balance);
   function ownerOf(uint256 _tokenId) public view returns (address _owner);
   function exists(uint256 _tokenId) public view returns (bool _exists);
 
   function approve(address _to, uint256 _tokenId) public;
-  function getApproved(uint256 _tokenId) public view returns (address _operator);
+  function getApproved(uint256 _tokenId)
+    public view returns (address _operator);
 
   function setApprovalForAll(address _operator, bool _approved) public;
-  function isApprovedForAll(address _owner, address _operator) public view returns (bool);
+  function isApprovedForAll(address _owner, address _operator)
+    public view returns (bool);
 
   function transferFrom(address _from, address _to, uint256 _tokenId) public;
-  function safeTransferFrom(address _from, address _to, uint256 _tokenId) public;
+  function safeTransferFrom(address _from, address _to, uint256 _tokenId)
+    public;
+
   function safeTransferFrom(
     address _from,
     address _to,

contracts/token/ERC721/ERC721Holder.sol

@@ -4,7 +4,7 @@ import "./ERC721Receiver.sol";
 
 
 contract ERC721Holder is ERC721Receiver {
-  function onERC721Received(address, uint256, bytes) public returns(bytes4) {
+  function onERC721Received(address, address, uint256, bytes) public returns(bytes4) {
     return ERC721_RECEIVED;
   }
 }

contracts/token/ERC721/ERC721Receiver.sol

@@ -9,22 +9,30 @@ pragma solidity ^0.4.21;
 contract ERC721Receiver {
   /**
    * @dev Magic value to be returned upon successful reception of an NFT
-   *  Equals to `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`,
+   *  Equals to `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`,
    *  which can be also obtained as `ERC721Receiver(0).onERC721Received.selector`
    */
-  bytes4 constant ERC721_RECEIVED = 0xf0b9e5ba;
+  bytes4 internal constant ERC721_RECEIVED = 0x150b7a02;
 
   /**
    * @notice Handle the receipt of an NFT
    * @dev The ERC721 smart contract calls this function on the recipient
    * after a `safetransfer`. This function MAY throw to revert and reject the
-   *  transfer. This function MUST use 50,000 gas or less. Return of other
-   *  than the magic value MUST result in the transaction being reverted.
+   * transfer. Return of other than the magic value MUST result in the 
+   * transaction being reverted.
    * Note: the contract address is always the message sender.
-   * @param _from The sending address
+   * @param _operator The address which called `safeTransferFrom` function
+   * @param _from The address which previously owned the token
    * @param _tokenId The NFT identifier which is being transfered
    * @param _data Additional data with no specified format
-   * @return `bytes4(keccak256("onERC721Received(address,uint256,bytes)"))`
+   * @return `bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))`
    */
-  function onERC721Received(address _from, uint256 _tokenId, bytes _data) public returns(bytes4);
+  function onERC721Received(
+    address _operator,
+    address _from,
+    uint256 _tokenId,
+    bytes _data
+  )
+    public
+    returns(bytes4);
 }

contracts/token/ERC721/ERC721Token.sol

@@ -2,6 +2,7 @@ pragma solidity ^0.4.21;
 
 import "./ERC721.sol";
 import "./ERC721BasicToken.sol";
+import "../../introspection/ERC165.sol";
 import "zos-lib/contracts/migrations/Migratable.sol";
 
 
@@ -11,7 +12,24 @@ import "zos-lib/contracts/migrations/Migratable.sol";
  * Moreover, it includes approve all functionality using operator terminology
  * @dev see https://github.com/ethereum/EIPs/blob/master/EIPS/eip-721.md
  */
-contract ERC721Token is Migratable, ERC721, ERC721BasicToken {
+contract ERC721Token is Migratable, ERC165Support, ERC721BasicToken, ERC721 {
+
+  bytes4 private constant InterfaceId_ERC721Enumerable = 0x780e9d63;
+  /**
+   * 0x780e9d63 ===
+   *   bytes4(keccak256('totalSupply()')) ^
+   *   bytes4(keccak256('tokenOfOwnerByIndex(address,uint256)')) ^
+   *   bytes4(keccak256('tokenByIndex(uint256)'))
+   */
+
+  bytes4 private constant InterfaceId_ERC721Metadata = 0x5b5e139f;
+  /**
+   * 0x5b5e139f ===
+   *   bytes4(keccak256('name()')) ^
+   *   bytes4(keccak256('symbol()')) ^
+   *   bytes4(keccak256('tokenURI(uint256)'))
+   */
+
   // Token name
   string internal name_;
 
@@ -19,7 +37,7 @@ contract ERC721Token is Migratable, ERC721, ERC721BasicToken {
   string internal symbol_;
 
   // Mapping from owner to list of owned token IDs
-  mapping (address => uint256[]) internal ownedTokens;
+  mapping(address => uint256[]) internal ownedTokens;
 
   // Mapping from token ID to index of the owner tokens list
   mapping(uint256 => uint256) internal ownedTokensIndex;
@@ -41,11 +59,20 @@ contract ERC721Token is Migratable, ERC721, ERC721BasicToken {
     symbol_ = _symbol;
   }
 
+  function _supportsInterface(bytes4 _interfaceId)
+    internal
+    view
+    returns (bool)
+  {
+    return super._supportsInterface(_interfaceId) || 
+      _interfaceId == InterfaceId_ERC721Enumerable || _interfaceId == InterfaceId_ERC721Metadata;
+  }
+
   /**
    * @dev Gets the token name
    * @return string representing the token name
    */
-  function name() public view returns (string) {
+  function name() external view returns (string) {
     return name_;
   }
 
@@ -53,13 +80,13 @@ contract ERC721Token is Migratable, ERC721, ERC721BasicToken {
    * @dev Gets the token symbol
    * @return string representing the token symbol
    */
-  function symbol() public view returns (string) {
+  function symbol() external view returns (string) {
     return symbol_;
   }
 
   /**
    * @dev Returns an URI for a given token ID
-   * @dev Throws if the token ID does not exist. May return an empty string.
+   * Throws if the token ID does not exist. May return an empty string.
    * @param _tokenId uint256 ID of the token to query
    */
   function tokenURI(uint256 _tokenId) public view returns (string) {
@@ -73,7 +100,14 @@ contract ERC721Token is Migratable, ERC721, ERC721BasicToken {
    * @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 returns (uint256) {
+  function tokenOfOwnerByIndex(
+    address _owner,
+    uint256 _index
+  )
+    public
+    view
+    returns (uint256)
+  {
     require(_index < balanceOf(_owner));
     return ownedTokens[_owner][_index];
   }
@@ -88,7 +122,7 @@ contract ERC721Token is Migratable, ERC721, ERC721BasicToken {
 
   /**
    * @dev Gets the token ID at a given index of all the tokens in this contract
-   * @dev Reverts if the index is greater or equal to the total number of tokens
+   * 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
    */
@@ -99,7 +133,7 @@ contract ERC721Token is Migratable, ERC721, ERC721BasicToken {
 
   /**
    * @dev Internal function to set the token URI for a given token
-   * @dev Reverts if the token ID does not exist
+   * Reverts if the token ID does not exist
    * @param _tokenId uint256 ID of the token to set its URI
    * @param _uri string URI to assign
    */
@@ -145,7 +179,7 @@ contract ERC721Token is Migratable, ERC721, ERC721BasicToken {
 
   /**
    * @dev Internal function to mint a new token
-   * @dev Reverts if the given token ID already exists
+   * Reverts if the given token ID already exists
    * @param _to address the beneficiary that will own the minted token
    * @param _tokenId uint256 ID of the token to be minted by the msg.sender
    */
@@ -158,7 +192,7 @@ contract ERC721Token is Migratable, ERC721, ERC721BasicToken {
 
   /**
    * @dev Internal function to burn a specific token
-   * @dev Reverts if the token does not exist
+   * Reverts if the token does not exist
    * @param _owner owner of the token to burn
    * @param _tokenId uint256 ID of the token being burned by the msg.sender
    */

test/helpers/makeInterfaceId.js

+import { soliditySha3 } from 'web3-utils';
+
+const INTERFACE_ID_LENGTH = 4;
+
+export default (interfaces = []) => {
+  const interfaceIdBuffer = interfaces
+    .map(methodSignature => soliditySha3(methodSignature)) // keccak256
+    .map(h =>
+      Buffer
+        .from(h.substring(2), 'hex')
+        .slice(0, 4) // bytes4()
+    )
+    .reduce((memo, bytes) => {
+      for (let i = 0; i < INTERFACE_ID_LENGTH; i++) {
+        memo[i] = memo[i] ^ bytes[i]; // xor
+      }
+      return memo;
+    }, Buffer.alloc(INTERFACE_ID_LENGTH));
+
+  return `0x${interfaceIdBuffer.toString('hex')}`;
+};

test/introspection/SupportsInterface.behavior.js

+import makeInterfaceId from '../helpers/makeInterfaceId';
+
+const INTERFACE_IDS = {
+  ERC165: makeInterfaceId([
+    'supportsInterface(bytes4)',
+  ]),
+  ERC721: makeInterfaceId([
+    'balanceOf(address)',
+    'ownerOf(uint256)',
+    'approve(address,uint256)',
+    'getApproved(uint256)',
+    'setApprovalForAll(address,bool)',
+    'isApprovedForAll(address,address)',
+    'transferFrom(address,address,uint256)',
+    'safeTransferFrom(address,address,uint256)',
+    'safeTransferFrom(address,address,uint256,bytes)',
+  ]),
+  ERC721Enumerable: makeInterfaceId([
+    'totalSupply()',
+    'tokenOfOwnerByIndex(address,uint256)',
+    'tokenByIndex(uint256)',
+  ]),
+  ERC721Metadata: makeInterfaceId([
+    'name()',
+    'symbol()',
+    'tokenURI(uint256)',
+  ]),
+  ERC721Exists: makeInterfaceId([
+    'exists(uint256)',
+  ]),
+};
+
+export default function (interfaces = []) {
+  describe('ERC165\'s supportsInterface(bytes4)', function () {
+    beforeEach(function () {
+      this.thing = this.mock || this.token;
+    });
+
+    for (let k of interfaces) {
+      const interfaceId = INTERFACE_IDS[k];
+      describe(k, function () {
+        it('should use less than 30k gas', async function () {
+          const gasEstimate = await this.thing.supportsInterface.estimateGas(interfaceId);
+          gasEstimate.should.be.lte(30000);
+        });
+
+        it('is supported', async function () {
+          const isSupported = await this.thing.supportsInterface(interfaceId);
+          isSupported.should.eq(true);
+        });
+      });
+    }
+  });
+}

test/token/ERC721/ERC721MintBurn.behaviour.js

@@ -99,17 +99,6 @@ export default function shouldMintAndBurnERC721Token (accounts) {
           const approvedAccount = await this.token.getApproved(tokenId);
           approvedAccount.should.be.equal(ZERO_ADDRESS);
         });
-
-        it('emits an approval event', async function () {
-          logs.length.should.be.equal(2);
-
-          logs[0].event.should.be.eq('Approval');
-          logs[0].args._owner.should.be.equal(sender);
-          logs[0].args._approved.should.be.equal(ZERO_ADDRESS);
-          logs[0].args._tokenId.should.be.bignumber.equal(tokenId);
-
-          logs[1].event.should.be.eq('Transfer');
-        });
       });
 
       describe('when the given token ID was not tracked by this contract', function () {

test/token/ERC721/ERC721Token.test.js

 import assertRevert from '../../helpers/assertRevert';
 import shouldBehaveLikeERC721BasicToken from './ERC721BasicToken.behaviour';
 import shouldMintAndBurnERC721Token from './ERC721MintBurn.behaviour';
+import shouldSupportInterfaces from '../../introspection/SupportsInterface.behavior';
 import _ from 'lodash';
 
 const BigNumber = web3.BigNumber;
@@ -196,4 +197,12 @@ contract('ERC721Token', function (accounts) {
       });
     });
   });
+
+  shouldSupportInterfaces([
+    'ERC165',
+    'ERC721',
+    'ERC721Exists',
+    'ERC721Enumerable',
+    'ERC721Metadata',
+  ]);
 });