convert TokenVesting to initializers

contracts/drafts/TokenVesting.sol

@@ -2,6 +2,7 @@
 
 pragma solidity ^0.4.24;
 
+import "../Initializable.sol";
 import "../token/ERC20/SafeERC20.sol";
 import "../ownership/Ownable.sol";
 import "../math/SafeMath.sol";
@@ -13,7 +14,7 @@ import "../math/SafeMath.sol";
  * typical vesting scheme, with a cliff and vesting period. Optionally revocable by the
  * owner.
  */
-contract TokenVesting is Ownable {
+contract TokenVesting is Initializable, Ownable {
   using SafeMath for uint256;
   using SafeERC20 for IERC20;
 
@@ -42,7 +43,7 @@ contract TokenVesting is Ownable {
    * @param duration duration in seconds of the period in which the tokens will vest
    * @param revocable whether the vesting is revocable or not
    */
-  constructor(
+  function initialize(
     address beneficiary,
     uint256 start,
     uint256 cliffDuration,
@@ -50,7 +51,10 @@ contract TokenVesting is Ownable {
     bool revocable
   )
     public
+    initializer
   {
+    Ownable.initialize();
+
     require(beneficiary != address(0));
     require(cliffDuration <= duration);
 

contracts/mocks/TokenVestingMock.sol

@@ -0,0 +1,22 @@
+pragma solidity ^0.4.24;
+
+import "../Initializable.sol";
+import "../drafts/TokenVesting.sol";
+
+contract TokenVestingMock is Initializable, TokenVesting {
+  constructor(
+    address beneficiary,
+    uint256 start,
+    uint256 cliffDuration,
+    uint256 duration,
+    bool revocable
+  ) public {
+    TokenVesting.initialize(
+      beneficiary,
+      start,
+      cliffDuration,
+      duration,
+      revocable
+    );
+  }
+}

test/token/ERC20/TokenVesting.test.js

@@ -10,8 +10,8 @@ require('chai')
   .use(require('chai-bignumber')(BigNumber))
   .should();
 
-const ERC20Mintable = artifacts.require('ERC20Mintable');
-const TokenVesting = artifacts.require('TokenVesting');
+const ERC20Mintable = artifacts.require('ERC20MintableMock');
+const TokenVesting = artifacts.require('TokenVestingMock');
 
 contract('TokenVesting', function ([_, owner, beneficiary]) {
   const amount = new BigNumber(1000);