MixinStakeStorage unit tests

contracts/staking/contracts/test/TestMixinStakeStorage.sol

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+/*
+
+  Copyright 2019 ZeroEx Intl.
+
+  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.
+
+*/
+
+pragma solidity ^0.5.9;
+pragma experimental ABIEncoderV2;
+
+import "../src/interfaces/IStructs.sol";
+import "../src/stake/MixinStakeStorage.sol";
+
+
+contract TestMixinStakeStorage is
+    MixinStakeStorage
+{
+    mapping (uint256 => IStructs.StoredBalance) public testBalances;
+
+    function setCurrentEpoch(uint256 newEpoch)
+        external
+    {
+        currentEpoch = newEpoch;
+    }
+
+    function moveStake(
+        uint256 fromIndex,
+        uint256 toIndex,
+        uint256 amount
+    )
+        external
+    {
+        return _moveStake(
+            testBalances[fromIndex],
+            testBalances[toIndex],
+            amount
+        );
+    }
+
+    function increaseCurrentAndNextBalance(uint256 index, uint256 amount)
+        external
+    {
+        return _increaseCurrentAndNextBalance(testBalances[index], amount);
+    }
+
+    function decreaseCurrentAndNextBalance(uint256 index, uint256 amount)
+        external
+    {
+        _decreaseCurrentAndNextBalance(testBalances[index], amount);
+    }
+
+    function increaseNextBalance(uint256 index, uint256 amount)
+        external
+    {
+        _increaseNextBalance(testBalances[index], amount);
+    }
+
+    function decreaseNextBalance(uint256 index, uint256 amount)
+        external
+    {
+        _decreaseNextBalance(testBalances[index], amount);
+    }
+
+    function loadSyncedBalance(uint256 index)
+        external
+        returns (IStructs.StoredBalance memory balance)
+    {
+        return _loadSyncedBalance(testBalances[index]);
+    }
+
+    function loadUnsyncedBalance(uint256 index)
+        external
+        view
+        returns (IStructs.StoredBalance memory balance)
+    {
+        return _loadUnsyncedBalance(testBalances[index]);
+    }
+
+    function setStoredBalance(
+        IStructs.StoredBalance memory balance,
+        uint256 index
+    )
+        public
+    {
+        testBalances[index] = balance;
+    }
+}