guardedArrayReplace fix & simple tests

contracts/common/ArrayUtils.sol

@@ -29,7 +29,7 @@ library ArrayUtils {
     {
         byte[8] memory bitmasks = [byte(2 ** 7), byte(2 ** 6), byte(2 ** 5), byte(2 ** 4), byte(2 ** 3), byte(2 ** 2), byte(2 ** 1), byte(2 ** 0)];
         require(array.length == desired.length);
-        require(mask.length == array.length / 8);
+        require(mask.length >= array.length / 8);
         for (uint i = 0; i < array.length; i++ ) {
             /* 1-bit means value can be changed. */
             bool masked = (mask[i / 8] & bitmasks[i % 8]) == 0;

contracts/exchange/Exchange.sol

@@ -105,6 +105,14 @@ contract Exchange is LazyBank, ReentrancyGuarded {
     event OrderBidOn      (bytes32 hash, address indexed bidder, uint amount, uint timestamp);
     event OrdersMatched   (Order buy, Order sell);
 
+    function guardedArrayReplace(bytes array, bytes desired, bytes mask)
+        public
+        pure
+        returns (bytes)
+    {
+        return ArrayUtils.guardedArrayReplace(array, desired, mask);
+    }
+
     function chargeFee(address from, address to, uint amount)
         internal
     {

test/wyvern-exchange.js

@@ -63,6 +63,26 @@ const hashOrder = (order) => {
 */
 
 contract('WyvernExchange', (accounts) => {
+  it('should allow simple array replacement', () => {
+    return WyvernExchange
+      .deployed()
+      .then(exchangeInstance => {
+        return exchangeInstance.guardedArrayReplace.call('0xff', '0x00', '0xff').then(res => {
+          assert.equal(res, '0x00', 'Array was not properly replaced!')
+        })
+      })
+  })
+
+  it('should disallow array replacement', () => {
+    return WyvernExchange
+      .deployed()
+      .then(exchangeInstance => {
+        return exchangeInstance.guardedArrayReplace.call('0xff', '0x00', '0x00').then(res => {
+          assert.equal(res, '0xff', 'Array replacement was not disallowed!')
+        })
+      })
+  })
+
   const makeOrder = (exchange) => ({
     exchange: exchange,
     maker: accounts[0],