Start the serializationtest at a specivic turn

This enables to only test critical game sections.

binaries/system/readme.txt

@@ -77,7 +77,7 @@ Advanced / diagnostic:
 -ooslog             dumps simulation state in binary and ASCII representations each turn,
                     files created in sim_log within the game's log folder. NOTE: game will
                     run much slower with this option!
--serializationtest  checks simulation state each turn for serialization errors; on test
+-serializationtest=N checks simulation state for serialization errors starting at turn N; on test
                     failure, error is displayed and logs created in oos_log within the
                     game's log folder. NOTE: game will run much slower with this option!
 -rejointest=N       simulates a rejoin and checks simulation state each turn for serialization

source/main.cpp

@@ -659,8 +659,15 @@ static void RunGameOrAtlas(const std::span<const char* const> argv)
 		{
 			CReplayPlayer replay;
 			replay.Load(replayFile);
+			const int serializationTestTurn{[&] {
+				if (!args.Has("serializationtest"))
+					return -1;
+
+				const CStr str{args.Get("serializationtest")};
+				return str.empty() ? 0 : str.ToInt();
+			}()};
 			replay.Replay(
-				args.Has("serializationtest"),
+				serializationTestTurn,
 				args.Has("rejointest") ? args.Get("rejointest").ToInt() : -1,
 				args.Has("ooslog"),
 				!args.Has("hashtest-full") || args.Get("hashtest-full") == "true",

source/ps/GameSetup/Config.cpp

@@ -1,4 +1,4 @@
-/* Copyright (C) 2025 Wildfire Games.
+/* Copyright (C) 2026 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -91,7 +91,10 @@ static void ProcessCommandLineArgs(const CmdLineArgs& args)
 		g_ConfigDB.SetValueString(CFG_COMMAND, "ooslog", "true");
 
 	if (args.Has("serializationtest"))
-		g_ConfigDB.SetValueString(CFG_COMMAND, "serializationtest", "true");
+	{
+		const CStr str{args.Get("serializationtest")};
+		g_ConfigDB.SetValueString(CFG_COMMAND, "serializationtest", str.empty() ? "0" : str);
+	}
 
 	if (args.Has("rejointest"))
 		g_ConfigDB.SetValueString(CFG_COMMAND, "rejointest", args.Get("rejointest"));

source/ps/Replay.cpp

@@ -191,7 +191,8 @@ void CheckReplayMods(const std::vector<Mod::ModData>& replayMods)
 }
 } // anonymous namespace
 
-void CReplayPlayer::Replay(const bool serializationtest, const int rejointestturn, const bool ooslog, const bool testHashFull, const bool testHashQuick)
+void CReplayPlayer::Replay(const int serializationtestturn, const int rejointestturn, const bool ooslog,
+	const bool testHashFull, const bool testHashQuick)
 {
 	ENSURE(m_Stream);
 
@@ -249,12 +250,15 @@ void CReplayPlayer::Replay(const bool serializationtest, const int rejointesttur
 				MountMods(Paths(g_CmdLineArgs), g_Mods.GetEnabledMods());
 			}
 
-			if (serializationtest && rejointestturn >= 0)
+			if (serializationtestturn >= 0 && rejointestturn >= 0)
 				LOGERROR("serializationtest and rejointest can't be activ at the same time.");
 
 			SimulationDebugOptions debugOption{};
-			if (serializationtest)
-				debugOption.test = SimulationDebugOptions::SerializationTest{};
+			if (serializationtestturn >= 0)
+			{
+				debugOption.test =
+					SimulationDebugOptions::SerializationTest{serializationtestturn};
+			}
 			if (rejointestturn >= 0)
 				debugOption.test = SimulationDebugOptions::RejoinTest{rejointestturn};
 			if (ooslog)

source/ps/Replay.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2025 Wildfire Games.
+/* Copyright (C) 2026 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -114,7 +114,8 @@ public:
 	~CReplayPlayer();
 
 	void Load(const OsPath& path);
-	void Replay(const bool serializationtest, const int rejointestturn, const bool ooslog, const bool testHashFull, const bool testHashQuick);
+	void Replay(const int serializationtestturn, const int rejointestturn, const bool ooslog,
+		const bool testHashFull, const bool testHashQuick);
 
 private:
 	std::istream* m_Stream;

source/simulation2/Simulation2.cpp

@@ -82,10 +82,14 @@ public:
 		m_MapSettings{cx.GetGeneralJSContext()},
 		// Tests won't have config initialised
 		m_EnableOOSLog{debugOptions.oosLog || CConfigDB::GetIfInitialised("ooslog", false)},
-		m_EnableSerializationTest{
-			std::holds_alternative<SimulationDebugOptions::SerializationTest>(debugOptions.test) ||
-			CConfigDB::GetIfInitialised("serializationtest", false)},
 		// Handle bogus values of the arg
+		m_SerializationTestTurn{[&]
+		{
+			const auto* serializationTestOption{
+				std::get_if<SimulationDebugOptions::SerializationTest>(&debugOptions.test)};
+			return serializationTestOption ? serializationTestOption->turn :
+				std::max(CConfigDB::GetIfInitialised("serializationtest", -1), -1);
+		}()},
 		m_RejoinTestTurn{[&]() -> std::optional<int>
 		{
 			const auto* rejoinTestOption{
@@ -164,6 +168,8 @@ public:
 
 	// Functions and data for the serialization test mode: (see Update() for relevant comments)
 
+	std::optional<int> m_SerializationTestTurn;
+	bool m_TestingSerialization{false};
 	bool m_EnableSerializationTest{false};
 	std::optional<int> m_RejoinTestTurn;
 	bool m_TestingRejoin{false};
@@ -392,12 +398,16 @@ void CSimulation2Impl::Update(int turnLength, const std::vector<SimulationComman
 	SerializationTestState primaryStateBefore;
 	const ScriptInterface& scriptInterface = m_ComponentManager.GetScriptInterface();
 
+	const bool startSerializationTest = m_SerializationTestTurn.has_value() &&
+		std::cmp_equal(m_SerializationTestTurn.value(), m_TurnNumber);
+	if (startSerializationTest)
+		m_TestingSerialization = true;
 	const bool startRejoinTest = m_RejoinTestTurn.has_value() &&
 		static_cast<int64_t>(m_RejoinTestTurn.value()) == m_TurnNumber;
 	if (startRejoinTest)
 		m_TestingRejoin = true;
 
-	if (m_EnableSerializationTest || m_TestingRejoin)
+	if (m_TestingSerialization || m_TestingRejoin)
 	{
 		ENSURE(m_ComponentManager.SerializeState(primaryStateBefore.state));
 		if (serializationTestDebugDump)
@@ -408,8 +418,10 @@ void CSimulation2Impl::Update(int turnLength, const std::vector<SimulationComman
 
 	UpdateComponents(m_SimContext, turnLengthFixed, commands);
 
-	if (m_EnableSerializationTest || startRejoinTest)
+	if (m_TestingSerialization || startRejoinTest)
 	{
+		if (startSerializationTest)
+			debug_printf("Starting serializationtest\n");
 		if (startRejoinTest)
 			debug_printf("Initializing the secondary simulation\n");
 
@@ -469,7 +481,7 @@ void CSimulation2Impl::Update(int turnLength, const std::vector<SimulationComman
 		ENSURE(m_SecondaryComponentManager->DeserializeState(primaryStateBefore.state));
 	}
 
-	if (m_EnableSerializationTest || m_TestingRejoin)
+	if (m_TestingSerialization || m_TestingRejoin)
 	{
 		SerializationTestState secondaryStateBefore;
 		ENSURE(m_SecondaryComponentManager->SerializeState(secondaryStateBefore.state));

source/simulation2/system/DebugOptions.h

@@ -1,4 +1,4 @@
-/* Copyright (C) 2025 Wildfire Games.
+/* Copyright (C) 2026 Wildfire Games.
  * This file is part of 0 A.D.
  *
  * 0 A.D. is free software: you can redistribute it and/or modify
@@ -22,7 +22,10 @@
 
 struct SimulationDebugOptions
 {
-	struct SerializationTest {};
+	struct SerializationTest
+	{
+		int turn;
+	};
 	struct RejoinTest
 	{
 		int turn;