完善mock和测试

git-svn-id: http://code.alibabatech.com/svn/druid/trunk@789 b9813039-fb51-4c41-a8b9-e21c2acb5095

src/main/java/com/alibaba/druid/mock/MockResultSet.java

@@ -404,7 +404,9 @@ public class MockResultSet implements ResultSet {
 
     @Override
     public boolean isAfterLast() throws SQLException {
-
+        if (closed) {
+            throw new SQLException();
+        }
         return false;
     }