完善mock和测试

git-svn-id: http://code.alibabatech.com/svn/druid/trunk@808 b9813039-fb51-4c41-a8b9-e21c2acb5095

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

@@ -70,6 +70,10 @@ public class MockCallableStatement extends MockPreparedStatement implements Call
 
     @Override
     public boolean wasNull() throws SQLException {
+        if (closed) {
+            throw new SQLException();
+        }
+        
         return wasNull;
     }