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

test/token/ERC20/ERC20.test.js

@@ -1,5 +1,6 @@
 const { assertRevert } = require('../../helpers/assertRevert');
 const expectEvent = require('../../helpers/expectEvent');
+const { ZERO_ADDRESS } = require('../../helpers/constants');
 
 const ERC20Mock = artifacts.require('ERC20Mock');
 
@@ -10,8 +11,6 @@ require('chai')
   .should();
 
 contract('ERC20', function ([_, owner, recipient, anotherAccount]) {
-  const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
-
   beforeEach(async function () {
     this.token = await ERC20Mock.new(owner, 100);
   });

test/token/ERC20/TokenVesting.test.js

@@ -2,6 +2,7 @@ const { expectThrow } = require('../../helpers/expectThrow');
 const { EVMRevert } = require('../../helpers/EVMRevert');
 const time = require('../../helpers/time');
 const { ethGetBlock } = require('../../helpers/web3');
+const { ZERO_ADDRESS } = require('../../helpers/constants');
 
 const BigNumber = web3.BigNumber;
 
@@ -14,7 +15,6 @@ const TokenVesting = artifacts.require('TokenVesting');
 
 contract('TokenVesting', function ([_, owner, beneficiary]) {
   const amount = new BigNumber(1000);
-  const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
 
   beforeEach(async function () {
     // +1 minute so it starts after contract instantiation

test/token/ERC20/behaviors/ERC20Burnable.behavior.js

@@ -1,8 +1,8 @@
 const { assertRevert } = require('../../../helpers/assertRevert');
 const expectEvent = require('../../../helpers/expectEvent');
+const { ZERO_ADDRESS } = require('../../../helpers/constants');
 
 const BigNumber = web3.BigNumber;
-const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
 
 require('chai')
   .use(require('chai-bignumber')(BigNumber))

test/token/ERC20/behaviors/ERC20Mintable.behavior.js

@@ -1,5 +1,6 @@
 const { assertRevert } = require('../../../helpers/assertRevert');
 const expectEvent = require('../../../helpers/expectEvent');
+const { ZERO_ADDRESS } = require('../../../helpers/constants');
 
 const BigNumber = web3.BigNumber;
 
@@ -8,8 +9,6 @@ require('chai')
   .should();
 
 function shouldBehaveLikeERC20Mintable (minter, [anyone]) {
-  const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
-
   describe('as a mintable token', function () {
     describe('mint', function () {
       const amount = 100;

test/token/ERC721/ERC721.behavior.js

@@ -1,6 +1,7 @@
 const expectEvent = require('../../helpers/expectEvent');
 const { shouldSupportInterfaces } = require('../../introspection/SupportsInterface.behavior');
 const { assertRevert } = require('../../helpers/assertRevert');
+const { ZERO_ADDRESS } = require('../../helpers/constants');
 const { decodeLogs } = require('../../helpers/decodeLogs');
 const { sendTransaction } = require('../../helpers/sendTransaction');
 
@@ -19,7 +20,6 @@ function shouldBehaveLikeERC721 (
   const firstTokenId = 1;
   const secondTokenId = 2;
   const unknownTokenId = 3;
-  const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
   const RECEIVER_MAGIC_VALUE = '0x150b7a02';
 
   describe('like an ERC721', function () {

test/token/ERC721/ERC721MintBurn.behavior.js

@@ -1,5 +1,6 @@
 const { assertRevert } = require('../../helpers/assertRevert');
 const expectEvent = require('../../helpers/expectEvent');
+const { ZERO_ADDRESS } = require('../../helpers/constants');
 const BigNumber = web3.BigNumber;
 
 require('chai')
@@ -15,7 +16,6 @@ function shouldBehaveLikeMintAndBurnERC721 (
   const secondTokenId = 2;
   const thirdTokenId = 3;
   const unknownTokenId = 4;
-  const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
   const MOCK_URI = 'https://example.com';
 
   describe('like a mintable and burnable ERC721', function () {

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 () {