Improves Ownable events (OpenZeppelin#1397)

* signing prefix added

* Minor improvement

* Tests changed

* Successfully tested

* Minor improvements

* Minor improvements

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

This reverts commit a688977.

* updates

* fixes OpenZeppelin#1392

* event tests added

* constructor event added

(cherry picked from commit af42c39)

contracts/ownership/Ownable.sol

@@ -9,8 +9,6 @@ pragma solidity ^0.4.24;
 contract Ownable {
   address private _owner;
 
-
-  event OwnershipRenounced(address indexed previousOwner);
   event OwnershipTransferred(
     address indexed previousOwner,
     address indexed newOwner
@@ -23,6 +21,7 @@ contract Ownable {
    */
   constructor() public {
     _owner = msg.sender;
+    emit OwnershipTransferred(address(0), _owner);
   }
 
   /**
@@ -54,7 +53,7 @@ contract Ownable {
    * modifier anymore.
    */
   function renounceOwnership() public onlyOwner {
-    emit OwnershipRenounced(_owner);
+    emit OwnershipTransferred(_owner, address(0));
     _owner = address(0);
   }
 

test/ownership/Ownable.behavior.js

@@ -1,5 +1,6 @@
 const { expectThrow } = require('../helpers/expectThrow');
 const { EVMRevert } = require('../helpers/EVMRevert');
+const expectEvent = require('../helpers/expectEvent');
 
 const ZERO_ADDRESS = '0x0000000000000000000000000000000000000000';
 
@@ -14,7 +15,8 @@ function shouldBehaveLikeOwnable (owner, [anyone]) {
 
     it('changes owner after transfer', async function () {
       (await this.ownable.isOwner({ from: anyone })).should.be.equal(false);
-      await this.ownable.transferOwnership(anyone, { from: owner });
+      const { logs } = await this.ownable.transferOwnership(anyone, { from: owner });
+      expectEvent.inLogs(logs, 'OwnershipTransferred');
 
       (await this.ownable.owner()).should.equal(anyone);
       (await this.ownable.isOwner({ from: anyone })).should.be.equal(true);
@@ -29,7 +31,9 @@ function shouldBehaveLikeOwnable (owner, [anyone]) {
     });
 
     it('loses owner after renouncement', async function () {
-      await this.ownable.renounceOwnership({ from: owner });
+      const { logs } = await this.ownable.renounceOwnership({ from: owner });
+      expectEvent.inLogs(logs, 'OwnershipTransferred');
+
       (await this.ownable.owner()).should.equal(ZERO_ADDRESS);
     });