added a test helper with common constants (#1400)

* signing prefix added

* Minor improvement

* Tests changed

* Successfully tested

* Minor improvements

* Minor improvements

* Revert "Dangling commas are now required. (#1359)"

This reverts commit a6889776f4.

* updates

* fixes #1206

(cherry picked from commit 58a42443df)

test/token/ERC721/ERC721PausedToken.behavior.js

@@ -1,5 +1,6 @@
 const { assertRevert } = require('../../helpers/assertRevert');
 const { sendTransaction } = require('../../helpers/sendTransaction');
+const { ZERO_ADDRESS } = require('../../helpers/constants');
 
 const BigNumber = web3.BigNumber;
 
@@ -11,7 +12,6 @@ function shouldBehaveLikeERC721PausedToken (owner, [recipient, operator]) {
   const firstTokenId = 1;
   const mintedTokens = 1;
   const mockData = '0x42';
-  const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
 
   describe('like a paused ERC721', function () {
     beforeEach(async function () {