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/ownership/Ownable.behavior.js

@@ -1,8 +1,7 @@
 const { expectThrow } = require('../helpers/expectThrow');
 const { EVMRevert } = require('../helpers/EVMRevert');
 const expectEvent = require('../helpers/expectEvent');
-
-const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
+const { ZERO_ADDRESS } = require('../helpers/constants');
 
 require('chai')
   .should();