Add error if shuffle function doesnt return an expected result

lib/errors/spec.js

@@ -63,6 +63,9 @@ module.exports = [{
   }, {
     name: 'NeedMoreInfo',
     message: '{0}'
+  }, {
+    name: 'InvalidSorting',
+    message: 'The sorting function provided did not return the change output as one of the array elements'
   }, {
     name: 'InvalidOutputAmountSum',
     message: '{0}'

lib/transaction/transaction.js

@@ -831,9 +831,13 @@ Transaction.prototype.sortOutputs = function(sortingFunction) {
 
 Transaction.prototype._newOutputOrder = function(newOutputs) {
   var changeIndex = 0;
-  while (this.outputs[this._changeIndex] !== newOutputs[changeIndex]) {
+  var length = this.outputs.length;
+  while (changeIndex < length && this.outputs[this._changeIndex] !== newOutputs[changeIndex]) {
     changeIndex++;
   }
+  if (changeIndex === length) {
+    throw new errors.Transaction.InvalidSorting();
+  }
   this.outputs = newOutputs;
   this._changeIndex = changeIndex;
   return this;

test/transaction/transaction.js

@@ -665,6 +665,16 @@ describe('Transaction', function() {
 
       _.shuffle.restore();
     });
+
+    it('fails if the provided function does not work as expected', function() {
+      var sorting = function(array) {
+        return [];
+      };
+      expect(function() {
+        transaction.sortOutputs(sorting);
+      }).to.throw(errors.Transaction.InvalidSorting);
+    });
+
   });
 });