diff --git a/src/unittest/test_serveractiveobjectmgr.cpp b/src/unittest/test_serveractiveobjectmgr.cpp
index 85cfd119fff3..9e75f7f19033 100644
--- a/src/unittest/test_serveractiveobjectmgr.cpp
+++ b/src/unittest/test_serveractiveobjectmgr.cpp
@@ -19,8 +19,12 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 #include "activeobjectmgr.h"
 #include "catch.h"
+#include "irrTypes.h"
+#include "irr_aabb3d.h"
 #include "mock_serveractiveobject.h"
 #include <algorithm>
+#include <iterator>
+#include <random>
 #include <utility>
 
 #include "server/activeobjectmgr.h"
@@ -28,6 +32,7 @@ with this program; if not, write to the Free Software Foundation, Inc.,
 
 class TestServerActiveObjectMgr {
 	server::ActiveObjectMgr saomgr;
+	std::vector<u16> ids;
 
 public:
 
@@ -36,15 +41,30 @@ class TestServerActiveObjectMgr {
 	}
 
 	bool registerObject(std::unique_ptr<ServerActiveObject> obj) {
-		return saomgr.registerObject(std::move(obj));
+		auto *ptr = obj.get();
+		if (!saomgr.registerObject(std::move(obj)))
+			return false;
+		ids.push_back(ptr->getId());
+		return true;
 	}
 
 	void removeObject(u16 id) {
+		const auto it = std::find(ids.begin(), ids.end(), id);
+		REQUIRE(it != ids.end());
+		ids.erase(it);
 		saomgr.removeObject(id);
 	}
 
+	void updatePos(u16 id, const v3f &pos) {
+		auto *obj = saomgr.getActiveObject(id);
+		REQUIRE(obj != nullptr);
+		obj->setPos(pos);
+		saomgr.updatePos(pos, id); // HACK work around m_env == nullptr
+	}
+
 	void clear() {
 		saomgr.clear();
+		ids.clear();
 	}
 
 	ServerActiveObject *getActiveObject(u16 id) {
@@ -60,6 +80,82 @@ class TestServerActiveObjectMgr {
 	void getAddedActiveObjectsAroundPos(T&& arg) {
 		saomgr.getAddedActiveObjectsAroundPos(std::forward(arg));
 	}
+
+	// Testing
+
+	bool empty() {
+		return ids.empty();
+	}
+
+	template<class T>
+	u16 randomId(T &random) {
+		REQUIRE(!ids.empty());
+		std::uniform_int_distribution<u16> index(0, ids.size() - 1);
+		return ids[index(random)];
+	}
+
+	void getObjectsInsideRadiusNaive(const v3f &pos, float radius,
+			std::vector<ServerActiveObject *> &result) 
+	{
+		for (const auto &[id, obj] : saomgr.m_active_objects.iter()) {
+			if (obj->getBasePosition().getDistanceFromSQ(pos) <= radius * radius) {
+				result.push_back(obj.get());
+			}
+		}
+	}
+
+	void getObjectsInAreaNaive(const aabb3f &box,
+			std::vector<ServerActiveObject *> &result) 
+	{
+		for (const auto &[id, obj] : saomgr.m_active_objects.iter()) {
+			if (box.isPointInside(obj->getBasePosition())) {
+				result.push_back(obj.get());
+			}
+		}
+	}
+
+	constexpr static auto compare_by_id = [](auto *sao1, auto *sao2) -> bool {
+		return sao1->getId() < sao2->getId();
+	};
+
+	static void sortById(std::vector<ServerActiveObject *> &saos) {
+		std::sort(saos.begin(), saos.end(), compare_by_id);
+	}
+
+	void compareObjects(std::vector<ServerActiveObject *> &actual,
+			std::vector<ServerActiveObject *> &expected)
+	{
+		std::vector<ServerActiveObject *> unexpected, missing;
+		sortById(actual);
+		sortById(expected);
+
+		std::set_difference(actual.begin(), actual.end(),
+			expected.begin(), expected.end(),
+			std::back_inserter(unexpected), compare_by_id);
+
+		assert(unexpected.empty());
+
+		std::set_difference(expected.begin(), expected.end(),
+			actual.begin(), actual.end(),
+			std::back_inserter(missing), compare_by_id);
+		assert(missing.empty());
+	}
+
+	void compareObjectsInsideRadius(const v3f &pos, float radius)
+	{
+		std::vector<ServerActiveObject *> actual, expected;
+		saomgr.getObjectsInsideRadius(pos, radius, actual, nullptr);
+		getObjectsInsideRadiusNaive(pos, radius, expected);
+		compareObjects(actual, expected);
+	}
+
+	void compareObjectsInArea(const aabb3f &box)
+	{
+		std::vector<ServerActiveObject *> actual, expected;
+		saomgr.getObjectsInArea(box, actual, nullptr);
+		getObjectsInAreaNaive(box, expected);
+		compareObjects(actual, expected);
+	}
 };
 
 
@@ -190,4 +286,54 @@ TEST_CASE("server active object manager")
 
 		saomgr.clear();
 	}
+
+	SECTION("spatial index") {
+		TestServerActiveObjectMgr saomgr;
+		std::mt19937 gen(0xABCDEF);
+    	std::uniform_int_distribution<s32> coordinate(-1000, 1000);
+		const auto random_pos = [&]() {
+			return v3f(coordinate(gen), coordinate(gen), coordinate(gen));
+		};
+
+		std::uniform_int_distribution<u32> percent(0, 99);
+		const auto modify = [&](u32 p_insert, u32 p_delete, u32 p_update) {
+            const auto p = percent(gen);
+			if (p < p_insert) {
+				saomgr.registerObject(std::make_unique<MockServerActiveObject>(nullptr, random_pos()));
+			} else if (p < p_insert + p_delete) {
+				if (!saomgr.empty())
+					saomgr.removeObject(saomgr.randomId(gen));
+			} else if (p < p_insert + p_delete + p_update) {
+				if (!saomgr.empty())
+					saomgr.updatePos(saomgr.randomId(gen), random_pos());
+			}
+		};
+
+		const auto test_queries = [&]() {
+			std::uniform_real_distribution<f32> radius(0, 100);
+			saomgr.compareObjectsInsideRadius(random_pos(), radius(gen));
+
+			aabb3f box(random_pos(), random_pos());
+			box.repair();
+			saomgr.compareObjectsInArea(box);
+		};
+
+		// Grow: Insertion twice as likely as deletion
+		for (u32 i = 0; i < 3000; ++i) {
+			modify(50, 25, 25);
+			test_queries();
+		}
+
+		// Stagnate: Insertion and deletion equally likely
+		for (u32 i = 0; i < 3000; ++i) {
+			modify(25, 25, 50);
+			test_queries();
+		}
+
+		// Shrink: Deletion twice as likely as insertion
+		while (!saomgr.empty()) {
+			modify(25, 50, 25);
+			test_queries();
+		}
+	}
 }
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