Reward calculation clean up for zero gas.

contracts/gateway/EIP20CoGateway.sol

@@ -286,7 +286,7 @@ contract EIP20CoGateway is GatewayBase {
 
         require(
             _messageHash != bytes32(0),
-            "Message hash must not be zero"
+            "Message hash must not be zero."
         );
 
         MessageBus.Message storage message = messages[_messageHash];
@@ -303,7 +303,7 @@ contract EIP20CoGateway is GatewayBase {
         stakeAmount_,
         mintedAmount_,
         rewardAmount_) =
-        progressMintInternal(_messageHash, initialGas, true, bytes32(0));
+        progressMintInternal(_messageHash, initialGas, false, _unlockSecret);
     }
 
     /**
@@ -745,6 +745,7 @@ contract EIP20CoGateway is GatewayBase {
         );
     }
 
+
     /* Public functions */
 
     /**
@@ -1060,6 +1061,7 @@ contract EIP20CoGateway is GatewayBase {
 
     /**
      * @notice This is internal method for process minting contains common logic.
+     *         It doesn't mint reward if reward is 0.
      *
      * @param _messageHash Message hash.
      * @param _initialGas Initial gas during progress process.
@@ -1078,7 +1080,6 @@ contract EIP20CoGateway is GatewayBase {
      *                        from the total amount.
      * @return rewardAmount_ Reward amount that is transferred to facilitator.
      */
-
     function progressMintInternal(
         bytes32 _messageHash,
         uint256 _initialGas,
@@ -1116,11 +1117,13 @@ contract EIP20CoGateway is GatewayBase {
             mintedAmount_
         );
 
-        // Reward beneficiary with the reward amount.
-        UtilityTokenInterface(utilityToken).increaseSupply(
-            msg.sender,
-            rewardAmount_
-        );
+        if(rewardAmount_ > 0) {
+            // Reward beneficiary with the reward amount.
+            UtilityTokenInterface(utilityToken).increaseSupply(
+                msg.sender,
+                rewardAmount_
+            );
+        }
 
         // Delete the mint data.
         delete mints[_messageHash];

contracts/gateway/EIP20Gateway.sol

@@ -892,6 +892,9 @@ contract EIP20Gateway is GatewayBase {
         progressUnstakeInternal(_messageHash, initialGas, bytes32(0), true);
     }
 
+
+    /** External methods */
+
     /**
      * @notice Declare redeem revert intent.
      *         This will set message status to revoked. This method will also

contracts/gateway/UtilityTokenInterface.sol

@@ -61,4 +61,17 @@ contract UtilityTokenInterface {
      */
     function decreaseSupply(uint256 _amount) external returns (bool success_);
 
+    /**
+     * @notice Sets the CoGateway contract address.
+     *
+     * @dev Function requires:
+     *          - It is called by whitelisted workers.
+     *          - coGateway address is set only once.
+     *          - coGateway.utilityToken must match this contract.
+     *
+     * @param _coGateway CoGateway contract address.
+     *
+     */
+    function setCoGateway(address _coGateway) external returns (bool);
+
 }

contracts/test/TestEIP20CoGateway.sol

@@ -70,7 +70,7 @@ contract TestEIP20CoGateway is EIP20CoGateway {
     /* Public Functions */
 
     /**
-     * @notice It is used to set the message.
+     * @notice It is used to set the stake message.
      *
      * @dev This is used for testing purpose.
      *

contracts/test/TestEIP20Gateway.sol

@@ -48,7 +48,7 @@ contract TestEIP20Gateway is EIP20Gateway {
         StateRootInterface _core,
         uint256 _bounty,
         IsMemberInterface _membersManager,
-        address _burner
+        address payable _burner
     )
         EIP20Gateway(
             _token,

contracts/test/gateway/MockUtilityToken.sol

@@ -0,0 +1,66 @@
+pragma solidity ^0.5.0;
+
+// Copyright 2018 OpenST Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// ----------------------------------------------------------------------------
+//
+// http://www.simpletoken.org/
+//
+// ----------------------------------------------------------------------------
+
+import "../../gateway/UtilityToken.sol";
+
+/**
+ * @title MockUtilityToken contract.
+ *
+ * @notice This contract is used to mock certain functions of UtilityToken
+ *         contract.
+ */
+contract MockUtilityToken is UtilityToken {
+
+    /* Constructor */
+
+    /**
+     * @notice Constructor.
+     *
+     * @dev This is used for testing only.
+     *
+     * @param _token Address of branded token.
+     * @param _symbol Symbol of token.
+     * @param _name Name of token.
+     * @param _decimals Decimal of token.
+     * @param _membersManager Address of a contract that manages organization.
+     */
+    constructor(
+        EIP20Interface _token,
+        string memory _symbol,
+        string memory _name,
+        uint8 _decimals,
+        IsMemberInterface _membersManager
+    )
+        public
+        UtilityToken(_token, _symbol, _name, _decimals, _membersManager)
+    {}
+
+    /**
+     * @notice Set the CoGateway address for testing.
+     *
+     * @param _coGatewayAddress CoGateway address.
+     */
+    function setCoGatewayAddress(address _coGatewayAddress) external {
+        coGateway = _coGatewayAddress;
+    }
+
+}

contracts/test/gateway/TestUtilityToken.sol

@@ -29,16 +29,17 @@ import "../../gateway/UtilityToken.sol";
  *         contract.
  */
 contract TestUtilityToken is UtilityToken {
-    
+
     /* Constructor */
 
     /**
      * @dev This is used for testing by mocking certain variables.
      *
      * @param _token Address of branded token.
-     * @param _symbol Symbol of token
-     * @param _name Name of token
-     * @param _decimals Decimal of token
+     * @param _symbol Symbol of token.
+     * @param _name Name of token.
+     * @param _decimals Decimal of token.
+     * @param _membersManager Address of a contract that manages organization.
      */
     constructor(
         EIP20Interface _token,