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/access/roles/PublicRole.behavior.js

@@ -1,4 +1,5 @@
 const { assertRevert } = require('../../helpers/assertRevert');
+const { ZERO_ADDRESS } = require('../../helpers/constants');
 const expectEvent = require('../../helpers/expectEvent');
 
 require('chai')
@@ -10,7 +11,6 @@ function capitalize (str) {
 
 function shouldBehaveLikePublicRole (authorized, otherAuthorized, [anyone], rolename) {
   rolename = capitalize(rolename);
-  const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
 
   describe('should behave like public role', function () {
     beforeEach('check preconditions', async function () {