Add Unittests for subscription module (#488)

Fix #492

unittests/util/MockWsBase.h

@@ -0,0 +1,48 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2023, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#pragma once
+
+#include <webserver/WsBase.h>
+
+struct MockSession : public WsBase
+{
+    std::string message;
+    void
+    send(std::shared_ptr<Message> msg_type) override
+    {
+        message += std::string(msg_type->data());
+    }
+    MockSession(util::TagDecoratorFactory const& factory) : WsBase(factory)
+    {
+    }
+};
+
+struct MockDeadSession : public WsBase
+{
+    void
+    send(std::shared_ptr<Message> msg_type) override
+    {
+        // err happen, the session should remove from subscribers
+        ec_.assign(2, boost::system::system_category());
+    }
+    MockDeadSession(util::TagDecoratorFactory const& factory) : WsBase(factory)
+    {
+    }
+};