Refactor ETL into smaller components (#649)

Fixes #666 and #664

unittests/util/MockLoadBalancer.h

@@ -0,0 +1,53 @@
+//------------------------------------------------------------------------------
+/*
+    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 <etl/Source.h>
+
+#include <boost/asio/spawn.hpp>
+#include <boost/json.hpp>
+#include <gmock/gmock.h>
+
+#include "org/xrpl/rpc/v1/xrp_ledger.grpc.pb.h"
+#include <grpcpp/grpcpp.h>
+
+#include <optional>
+
+class MockLoadBalancer
+{
+public:
+    MockLoadBalancer()
+    {
+    }
+
+    MOCK_METHOD(void, loadInitialLedger, (std::uint32_t, bool), ());
+
+    MOCK_METHOD(std::optional<org::xrpl::rpc::v1::GetLedgerResponse>, fetchLedger, (uint32_t, bool, bool), ());
+
+    MOCK_METHOD(bool, shouldPropagateTxnStream, (Source*), (const));
+
+    MOCK_METHOD(boost::json::value, toJson, (), (const));
+
+    MOCK_METHOD(
+        std::optional<boost::json::object>,
+        forwardToRippled,
+        (boost::json::object const&, std::string const&, boost::asio::yield_context&),
+        (const));
+};