test: Add unit test coverage for Init and Shutdown code

Currently this code is not called in unit tests. Calling should make it
possible to write tests for things like IPC exceptions being thrown during
shutdown.

src/test/CMakeLists.txt

@@ -64,6 +64,7 @@ add_executable(test_bitcoin
   net_peer_eviction_tests.cpp
   net_tests.cpp
   netbase_tests.cpp
+  node_init_tests.cpp
   node_warnings_tests.cpp
   orphanage_tests.cpp
   pcp_tests.cpp

src/test/node_init_tests.cpp

@@ -0,0 +1,51 @@
+// Copyright (c) 2025 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <init.h>
+#include <interfaces/init.h>
+#include <rpc/server.h>
+
+#include <boost/test/unit_test.hpp>
+#include <test/util/setup_common.h>
+
+using node::NodeContext;
+
+BOOST_FIXTURE_TEST_SUITE(node_init_tests, BasicTestingSetup)
+
+//! Custom implementation of interfaces::Init for testing.
+class TestInit : public interfaces::Init
+{
+public:
+    TestInit(NodeContext& node) : m_node(node)
+    {
+        InitContext(m_node);
+        m_node.init = this;
+    }
+    std::unique_ptr<interfaces::Chain> makeChain() override { return interfaces::MakeChain(m_node); }
+    std::unique_ptr<interfaces::WalletLoader> makeWalletLoader(interfaces::Chain& chain) override
+    {
+        return MakeWalletLoader(chain, *Assert(m_node.args));
+    }
+    NodeContext& m_node;
+};
+
+BOOST_AUTO_TEST_CASE(init_test)
+{
+    // Clear state set by BasicTestingSetup that AppInitMain assumes is unset.
+    LogInstance().DisconnectTestLogger();
+    m_node.args->SetConfigFilePath({});
+
+    // Prevent the test from trying to listen on ports 8332 and 8333.
+    m_node.args->ForceSetArg("-server", "0");
+    m_node.args->ForceSetArg("-listen", "0");
+
+    // Run through initialization and shutdown code.
+    TestInit init{m_node};
+    BOOST_CHECK(AppInitInterfaces(m_node));
+    BOOST_CHECK(AppInitMain(m_node));
+    Interrupt(m_node);
+    Shutdown(m_node);
+}
+
+BOOST_AUTO_TEST_SUITE_END()

src/test/util/setup_common.cpp

@@ -115,6 +115,14 @@ BasicTestingSetup::BasicTestingSetup(const ChainType chainType, TestOpts opts)
     if (!EnableFuzzDeterminism()) {
         SeedRandomForTest(SeedRand::FIXED_SEED);
     }
+
+    // Reset globals
+    fDiscover = true;
+    fListen = true;
+    SetRPCWarmupStarting();
+    g_reachable_nets.Reset();
+    ClearLocal();
+
     m_node.shutdown_signal = &m_interrupt;
     m_node.shutdown_request = [this]{ return m_interrupt(); };
     m_node.args = &gArgs;
@@ -214,7 +222,10 @@ BasicTestingSetup::~BasicTestingSetup()
     } else {
         fs::remove_all(m_path_root);
     }
+    // Clear all arguments except for -datadir, which GUI tests currently rely
+    // on to be set even after the testing setup is destroyed.
     gArgs.ClearArgs();
+    gArgs.ForceSetArg("-datadir", fs::PathToString(m_path_root));
 }
 
 ChainTestingSetup::ChainTestingSetup(const ChainType chainType, TestOpts opts)