Redeem Pool and Redeemer Proxy unit tests

contracts/gateway/RedeemPool.sol

@@ -361,7 +361,7 @@ contract RedeemPool is Organized, Mutex {
         RedeemerProxy redeemerProxy = redeemerProxies[msg.sender];
         require(
             address(redeemerProxy) != address(0),
-            "Redeem proxy does not exist for the caller."
+            "Redeemer proxy does not exist for the caller."
         );
         // Resetting the proxy address of the redeemer.
         delete redeemerProxies[msg.sender];

contracts/gateway/RedeemerProxy.sol

@@ -162,7 +162,7 @@ contract RedeemerProxy is Mutex {
     {
         require(
             address(_token) != address(0),
-            "The token address may not be address zero."
+            "The token address must not be address zero."
         );
         require(
             _token.transfer(_to, _value),

contracts/test/gateway/MockRedeemerProxy.sol

@@ -0,0 +1,48 @@
+pragma solidity ^0.5.0;
+
+// Copyright 2019 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/
+//
+// ----------------------------------------------------------------------------
+
+/**
+ * @title MockRedeemerProxy is a contract used for unit testing of RedeemPool
+ *        method `destructStakerProxy`.
+ */
+contract MockRedeemerProxy {
+
+    /* Storage */
+
+    /** Flag to assert if self destruct is called. */
+    bool public selfDestruted;
+
+
+    /* Special Functions */
+
+    constructor () public {
+        selfDestruted = false;
+    }
+
+    /**
+     * @notice Mock method called from redeem pool during unit testing of
+     *         `destructRedeemerProxy`.
+     */
+    function selfDestruct() external {
+        selfDestruted = true;
+    }
+}

contracts/test/gateway/SpyEIP20CoGateway.sol

@@ -0,0 +1,90 @@
+pragma solidity ^0.5.0;
+
+// Copyright 2019 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 "./SpyToken.sol";
+
+/**
+ * @title A test double co-gateway where you can check sent values.
+ *
+ * @notice Use this spy if you need to investigate which values were sent to
+ *         the co-gateway.
+ */
+contract SpyEIP20CoGateway {
+
+    SpyToken public utilityToken;
+    uint256 public expectedNonce = 1;
+    uint256 public bounty = 100;
+    uint256 public amount;
+    address public beneficiary;
+    uint256 public gasPrice;
+    uint256 public gasLimit;
+    uint256 public nonce;
+    bytes32 public hashLock;
+
+    constructor() public {
+        utilityToken = new SpyToken();
+    }
+
+    /**
+     *  This method is used for testing. It returns fix nonce.
+     */
+    function getNonce(address) external view returns(uint256) {
+        return expectedNonce;
+    }
+
+    /**
+     * @notice Used for testing of redeem feature. This method spy on co-gateway redeem.
+     *
+     *
+     * @param _amount Redeem amount that will be transferred from redeemer
+     *                account.
+     * @param _beneficiary The address in the origin chain where the value
+     *                     tok ens will be released.
+     * @param _gasPrice Gas price that redeemer is ready to pay to get the
+     *                  redeem process done.
+     * @param _gasLimit Gas limit that redeemer is ready to pay.
+     * @param _nonce Nonce of the redeemer address.
+     * @param _hashLock Hash Lock provided by the facilitator.
+     *
+     * @return messageHash_ Hash of message.
+     */
+    function redeem(
+            uint256 _amount,
+            address _beneficiary,
+            uint256 _gasPrice,
+            uint256 _gasLimit,
+            uint256 _nonce,
+            bytes32 _hashLock
+        )
+        external
+        payable
+        returns(bytes32)
+    {
+        amount = _amount;
+        beneficiary = _beneficiary;
+        gasPrice = _gasPrice;
+        gasLimit = _gasLimit;
+        nonce = _nonce;
+        hashLock = _hashLock;
+        return bytes32('1');
+    }
+}