完善mock和测试

git-svn-id: http://code.alibabatech.com/svn/druid/trunk@791 b9813039-fb51-4c41-a8b9-e21c2acb5095

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

@@ -346,6 +346,10 @@ public class MockResultSet implements ResultSet {
 
     @Override
     public ResultSetMetaData getMetaData() throws SQLException {
+        if (closed) {
+            throw new SQLException("resultSet closed");
+        }
+        
         return metaData;
     }