convert Crowdsale to initializers

contracts/crowdsale/Crowdsale.sol

@@ -1,5 +1,6 @@
 pragma solidity ^0.4.24;
 
+import "../Initializable.sol";
 import "../token/ERC20/IERC20.sol";
 import "../math/SafeMath.sol";
 import "../token/ERC20/SafeERC20.sol";
@@ -17,7 +18,7 @@ import "../token/ERC20/SafeERC20.sol";
  * the methods to add functionality. Consider using 'super' where appropriate to concatenate
  * behavior.
  */
-contract Crowdsale {
+contract Crowdsale is Initializable {
   using SafeMath for uint256;
   using SafeERC20 for IERC20;
 
@@ -50,6 +51,9 @@ contract Crowdsale {
     uint256 amount
   );
 
+  constructor(uint256 rate, address wallet, IERC20 token) public {
+  }
+
   /**
    * @param rate Number of token units a buyer gets per wei
    * @dev The rate is the conversion between wei and the smallest and indivisible
@@ -58,7 +62,7 @@ contract Crowdsale {
    * @param wallet Address where collected funds will be forwarded to
    * @param token Address of the token being sold
    */
-  constructor(uint256 rate, address wallet, IERC20 token) public {
+  function initialize(uint256 rate, address wallet, IERC20 token) public initializer {
     require(rate > 0);
     require(wallet != address(0));
     require(token != address(0));

contracts/mocks/CrowdsaleMock.sol

@@ -0,0 +1,11 @@
+pragma solidity ^0.4.24;
+
+import "../Initializable.sol";
+import "../crowdsale/Crowdsale.sol";
+
+
+contract CrowdsaleMock is Initializable, Crowdsale {
+  constructor(uint256 rate, address wallet, IERC20 token) public Crowdsale(rate, wallet, token) {
+    Crowdsale.initialize(rate, wallet, token);
+  }
+}

test/crowdsale/Crowdsale.test.js

@@ -8,8 +8,8 @@ const should = require('chai')
   .use(require('chai-bignumber')(BigNumber))
   .should();
 
-const Crowdsale = artifacts.require('Crowdsale');
-const SimpleToken = artifacts.require('SimpleToken');
+const Crowdsale = artifacts.require('CrowdsaleMock');
+const SimpleToken = artifacts.require('SimpleTokenMock');
 
 contract('Crowdsale', function ([_, investor, wallet, purchaser]) {
   const rate = new BigNumber(1);