完善mock和测试

git-svn-id: http://code.alibabatech.com/svn/druid/trunk@827 b9813039-fb51-4c41-a8b9-e21c2acb5095

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

@@ -0,0 +1,12 @@
+package com.alibaba.druid.mock;
+
+import java.sql.SQLException;
+
+public class MockConnectionClosedException extends SQLException {
+
+    private static final long serialVersionUID = 1L;
+
+    public MockConnectionClosedException() {
+        super();
+    }
+}