diff --git a/binaries/data/mods/public/simulation/components/Attack.js b/binaries/data/mods/public/simulation/components/Attack.js
index 50523da650..6e6b2cfc82 100644
--- a/binaries/data/mods/public/simulation/components/Attack.js
+++ b/binaries/data/mods/public/simulation/components/Attack.js
@@ -440,9 +440,8 @@ Attack.prototype.GetBonusTemplate = function(type)
 	let template = this.template[type];
 	if (!template)
 		template = this.template[type.split(".")[0]].Splash;
-	if (template.Bonuses)
-		return clone(template.Bonuses);
-	return null;
+
+	return template.Bonuses || null;
 };
 
 /**
diff --git a/binaries/data/mods/public/simulation/components/DeathDamage.js b/binaries/data/mods/public/simulation/components/DeathDamage.js
index b145ecc1c2..d1494e8860 100644
--- a/binaries/data/mods/public/simulation/components/DeathDamage.js
+++ b/binaries/data/mods/public/simulation/components/DeathDamage.js
@@ -57,9 +57,7 @@ DeathDamage.prototype.GetDeathDamageStrengths = function()
 
 DeathDamage.prototype.GetBonusTemplate = function()
 {
-	if (this.template.Bonuses)
-		return clone(this.template.Bonuses);
-	return null;
+	return this.template.Bonuses || null;
 };
 
 DeathDamage.prototype.CauseDeathDamage = function()
diff --git a/binaries/data/mods/public/simulation/components/tests/setup.js b/binaries/data/mods/public/simulation/components/tests/setup.js
index 6497991c3e..c7849b8c44 100644
--- a/binaries/data/mods/public/simulation/components/tests/setup.js
+++ b/binaries/data/mods/public/simulation/components/tests/setup.js
@@ -8,23 +8,23 @@ var g_Components = {};
 Engine.RegisterComponentType = function(iid, name, ctor)
 {
 	TS_ASSERT(!g_ComponentTypes[name]);
-	g_ComponentTypes[name] = { iid: iid, ctor: ctor };
+	g_ComponentTypes[name] = { "iid": iid, "ctor": ctor };
 };
 
 Engine.RegisterSystemComponentType = function(iid, name, ctor)
 {
 	TS_ASSERT(!g_ComponentTypes[name]);
-	g_ComponentTypes[name] = { iid: iid, ctor: ctor };
+	g_ComponentTypes[name] = { "iid": iid, "ctor": ctor };
 };
 
 Engine.RegisterInterface = function(name)
 {
-	global["IID_"+name] = g_NewIID++;
+	global["IID_" + name] = g_NewIID++;
 };
 
 Engine.RegisterMessageType = function(name)
 {
-	global["MT_"+name] = g_NewMTID++;
+	global["MT_" + name] = g_NewMTID++;
 };
 
 Engine.QueryInterface = function(ent, iid)
@@ -41,9 +41,9 @@ Engine.RegisterGlobal = function(name, value)
 
 Engine.DestroyEntity = function(ent)
 {
-	for (var cid in g_Components[ent])
+	for (let cid in g_Components[ent])
 	{
-		var cmp = g_Components[ent][cid];
+		let cmp = g_Components[ent][cid];
 		if (cmp && cmp.Deinit)
 			cmp.Deinit();
 	}
@@ -85,9 +85,23 @@ global.DeleteMock = function(ent, iid)
 
 global.ConstructComponent = function(ent, name, template)
 {
-	var cmp = new g_ComponentTypes[name].ctor();
-	cmp.entity = ent;
-	cmp.template = template;
+	let cmp = new g_ComponentTypes[name].ctor();
+
+	Object.defineProperties(cmp, {
+		"entity": {
+			"value": ent,
+			"configurable": false,
+			"enumerable": false,
+			"writable": false
+		},
+		"template": {
+			"value": template && deepfreeze(clone(template)),
+			"configurable": false,
+			"enumerable": false,
+			"writable": false
+		}
+	});
+
 	cmp.Init();
 
 	if (!g_Components[ent])
diff --git a/binaries/data/mods/public/simulation/components/tests/setup_test.js b/binaries/data/mods/public/simulation/components/tests/setup_test.js
new file mode 100644
index 0000000000..cd90ce7016
--- /dev/null
+++ b/binaries/data/mods/public/simulation/components/tests/setup_test.js
@@ -0,0 +1,24 @@
+Engine.RegisterInterface("TestSetup");
+
+function TestSetup() {};
+TestSetup.prototype.Init = function() {};
+
+Engine.RegisterSystemComponentType(IID_TestSetup, "TestSetup", TestSetup);
+let cmpTestSetup = ConstructComponent(SYSTEM_ENTITY, "TestSetup", { "property": "value" });
+
+function expectException(func)
+{
+	try {
+		func();
+		Engine.TS_FAIL("Missed exception at " + new Error().stack);
+	} catch (e) {}
+}
+
+expectException(() => { cmpTestSetup.template = "replacement forbidden"; });
+expectException(() => { cmpTestSetup.template.property = "modification forbidden"; });
+expectException(() => { cmpTestSetup.template.other_property = "insertion forbidden"; });
+expectException(() => { delete cmpTestSetup.entity; });
+expectException(() => { delete cmpTestSetup.template; });
+expectException(() => { delete cmpTestSetup.template.property; });
+
+TS_ASSERT_UNEVAL_EQUALS(cmpTestSetup.template, { "property": "value" });
diff --git a/binaries/data/mods/public/simulation/components/tests/test_Attack.js b/binaries/data/mods/public/simulation/components/tests/test_Attack.js
index 5e9c82c601..d61979b93f 100644
--- a/binaries/data/mods/public/simulation/components/tests/test_Attack.js
+++ b/binaries/data/mods/public/simulation/components/tests/test_Attack.js
@@ -167,10 +167,6 @@ for (let className of ["Infantry", "Cavalry"])
 	attackComponentTest(className, true, (attacker, cmpAttack, defender) => {
 
 		TS_ASSERT_EQUALS(cmpAttack.GetBonusTemplate("Melee").BonusCav.Multiplier, 2);
-		// Check that we don't leak data
-		let bonus = cmpAttack.GetBonusTemplate("Melee");
-		bonus.BonusCav.Multiplier = 2.7;
-		TS_ASSERT_EQUALS(cmpAttack.GetBonusTemplate("Melee").BonusCav.Multiplier, 2);
 
 		TS_ASSERT(cmpAttack.GetBonusTemplate("Capture") === null);
 
diff --git a/binaries/data/mods/public/simulation/components/tests/test_DeathDamage.js b/binaries/data/mods/public/simulation/components/tests/test_DeathDamage.js
index a0edfeff15..05ab7f14cf 100644
--- a/binaries/data/mods/public/simulation/components/tests/test_DeathDamage.js
+++ b/binaries/data/mods/public/simulation/components/tests/test_DeathDamage.js
@@ -65,8 +65,10 @@ AddMock(deadEnt, IID_Ownership, {
 TS_ASSERT_UNEVAL_EQUALS(cmpDeathDamage.GetDeathDamageStrengths(), modifiedDamage);
 cmpDeathDamage.CauseDeathDamage();
 
+// Test splash damage bonus
 let splashBonus = { "BonusCav": { "Classes": "Cavalry", "Multiplier": 3 } };
-cmpDeathDamage.template.Bonuses = splashBonus;
+template.Bonuses = splashBonus;
+cmpDeathDamage = ConstructComponent(deadEnt, "DeathDamage", template);
 result.splashBonus = splashBonus;
 TS_ASSERT_UNEVAL_EQUALS(cmpDeathDamage.GetDeathDamageStrengths(), modifiedDamage);
 cmpDeathDamage.CauseDeathDamage();
diff --git a/binaries/data/mods/public/simulation/components/tests/test_GarrisonHolder.js b/binaries/data/mods/public/simulation/components/tests/test_GarrisonHolder.js
index f13e30b421..a2082ee0ad 100644
--- a/binaries/data/mods/public/simulation/components/tests/test_GarrisonHolder.js
+++ b/binaries/data/mods/public/simulation/components/tests/test_GarrisonHolder.js
@@ -133,8 +133,6 @@ TS_ASSERT_EQUALS(cmpGarrisonHolder.GetCapacity(), 10);
 TS_ASSERT_EQUALS(cmpGarrisonHolder.GetGarrisonedEntitiesCount(), 0);
 TS_ASSERT_EQUALS(cmpGarrisonHolder.CanPickup(unitToGarrisonId), false);
 
-cmpGarrisonHolder.template.Pickup = true;
-TS_ASSERT_EQUALS(cmpGarrisonHolder.CanPickup(unitToGarrisonId), true);
 TS_ASSERT_EQUALS(cmpGarrisonHolder.CanPickup(enemyUnitId), false);
 TS_ASSERT_EQUALS(cmpGarrisonHolder.IsFull(), false);
 TS_ASSERT_EQUALS(cmpGarrisonHolder.IsAllowedToGarrison(enemyUnitId), false);
diff --git a/source/simulation2/components/tests/test_scripts.h b/source/simulation2/components/tests/test_scripts.h
index 319a91b832..cb31cc6afb 100644
--- a/source/simulation2/components/tests/test_scripts.h
+++ b/source/simulation2/components/tests/test_scripts.h
@@ -66,6 +66,7 @@ public:
 
 		VfsPaths paths;
 		TS_ASSERT_OK(vfs::GetPathnames(g_VFS, L"simulation/components/tests/", L"test_*.js", paths));
+		paths.push_back(VfsPath(L"simulation/components/tests/setup_test.js"));
 		for (const VfsPath& path : paths)
 		{
 			CSimContext context;