Move NULL_BYTES to @0xproject/utils

packages/contracts/test/token_registry.ts

@@ -1,6 +1,6 @@
 import { ZeroEx } from '0x.js';
 import { BlockchainLifecycle, devConstants, web3Factory } from '@0xproject/dev-utils';
-import { BigNumber } from '@0xproject/utils';
+import { BigNumber, NULL_BYTES } from '@0xproject/utils';
 import { Web3Wrapper } from '@0xproject/web3-wrapper';
 import * as chai from 'chai';
 import ethUtil = require('ethereumjs-util');
@@ -66,8 +66,8 @@ describe('TokenRegistry', () => {
         name: '',
         symbol: '',
         decimals: 0,
-        ipfsHash: constants.NULL_BYTES,
-        swarmHash: constants.NULL_BYTES,
+        ipfsHash: NULL_BYTES,
+        swarmHash: NULL_BYTES,
     };
 
     describe('addToken', () => {

packages/contracts/util/constants.ts

@@ -4,7 +4,6 @@ const DUMMY_TOKEN_DECIMALS = 18;
 const DUMMY_TOKEN_TOTAL_SUPPLY = 0;
 
 export const constants = {
-    NULL_BYTES: '0x',
     INVALID_OPCODE: 'invalid opcode',
     REVERT: 'revert',
     TESTRPC_NETWORK_ID: 50,