diff --git a/modules/app/private/application.cpp b/modules/app/private/application.cpp
index c8ed190..1038001 100644
--- a/modules/app/private/application.cpp
+++ b/modules/app/private/application.cpp
@@ -5,11 +5,6 @@ namespace lt::app {
 
 void Application::game_loop()
 {
-	for (auto &system : m_systems)
-	{
-		system->init();
-	}
-
 	while (true)
 	{
 		for (auto &system : m_systems)
@@ -20,7 +15,12 @@ void Application::game_loop()
 			}
 		}
 
-		for (auto &system : m_systems_to_be_removed)
+		for (auto &system : m_systems_to_be_registered)
+		{
+			m_systems.emplace_back(system)->on_register();
+		}
+
+		for (auto &system : m_systems_to_be_unregistered)
 		{
 			m_systems.erase(
 			    std::remove(m_systems.begin(), m_systems.end(), system),
@@ -42,7 +42,7 @@ void Application::register_system(Ref<app::ISystem> system)
 
 void Application::unregister_system(Ref<app::ISystem> system)
 {
-	m_systems_to_be_removed.emplace_back(std::move(system));
+	m_systems_to_be_unregistered.emplace_back(std::move(system));
 }
 
 } // namespace lt::app
diff --git a/modules/app/public/application.hpp b/modules/app/public/application.hpp
index bc92196..fa4ba7d 100644
--- a/modules/app/public/application.hpp
+++ b/modules/app/public/application.hpp
@@ -35,7 +35,9 @@ protected:
 private:
 	std::vector<Ref<app::ISystem>> m_systems;
 
-	std::vector<Ref<app::ISystem>> m_systems_to_be_removed;
+	std::vector<Ref<app::ISystem>> m_systems_to_be_unregistered;
+
+	std::vector<Ref<app::ISystem>> m_systems_to_be_registered;
 };
 
 
diff --git a/modules/app/public/system.hpp b/modules/app/public/system.hpp
index 9a5b9a3..231fa88 100644
--- a/modules/app/public/system.hpp
+++ b/modules/app/public/system.hpp
@@ -17,7 +17,9 @@ public:
 
 	auto operator=(const ISystem &) -> ISystem & = delete;
 
-	virtual void init() = 0;
+	virtual void on_register() = 0;
+
+	virtual void on_unregister() = 0;
 
 	virtual auto tick() -> bool = 0;
 };
diff --git a/modules/debug/public/assertions.hpp b/modules/debug/public/assertions.hpp
index 7c49594..9d6f195 100644
--- a/modules/debug/public/assertions.hpp
+++ b/modules/debug/public/assertions.hpp
@@ -1,6 +1,8 @@
 #pragma once
 
+#include <format>
 #include <logger/logger.hpp>
+#include <source_location>
 
 namespace lt {
 
@@ -12,15 +14,6 @@ struct FailedAssertion: std::exception
 	}
 };
 
-template<typename Expression_T, typename... Args>
-constexpr void ensure(Expression_T &&expression, std::format_string<Args...> fmt, Args &&...args)
-{
-	if (!static_cast<bool>(expression))
-	{
-		Logger::log(LogLvl::critical, fmt, std::forward<Args>(args)...);
-		throw ::lt::FailedAssertion(__FILE__, __LINE__);
-	}
-}
 
 template<typename Expression_T>
 constexpr void ensure(Expression_T &&expression, const char *message)
diff --git a/modules/ecs/private/scene.cpp b/modules/ecs/private/scene.cpp
index 9a58c1f..49168d5 100644
--- a/modules/ecs/private/scene.cpp
+++ b/modules/ecs/private/scene.cpp
@@ -11,21 +11,6 @@ auto Scene::create_entity(const std::string &name, const TransformComponent &tra
 
 auto Scene::get_entity_by_tag(const std::string &tag) -> Entity
 {
-	// TagComponent tagComp(tag);
-	// entt::entity entity = entt::to_entity(m_registry, tagComp);
-	auto entity = Entity {};
-
-	m_registry.view<TagComponent>().each([&](TagComponent &tagComp) {
-		// if (tagComp.tag == tag)
-		// 	entity = entity(entt::to_entity(m_registry, tagComp), this);
-	});
-
-	if (entity.is_valid())
-	{
-		return entity;
-	}
-
-	ensure(false, "Scene::get_entity_by_tag: failed to find entity by tag: {}", tag);
 	return {};
 }
 
diff --git a/modules/ecs/public/scene.hpp b/modules/ecs/public/scene.hpp
index 311f702..2d8bf7c 100644
--- a/modules/ecs/public/scene.hpp
+++ b/modules/ecs/public/scene.hpp
@@ -19,6 +19,12 @@ public:
 		return m_registry.group(entt::get<T...>);
 	}
 
+	template<typename T>
+	auto view()
+	{
+		return m_registry.view<T>();
+	}
+
 	auto create_entity(
 	    const std::string &name,
 	    const TransformComponent &transform = TransformComponent()
@@ -31,6 +37,7 @@ public:
 		return m_registry;
 	}
 
+
 private:
 	friend class Entity;
 
diff --git a/modules/math/public/algebra.hpp b/modules/math/public/algebra.hpp
index 895bd67..af2ed26 100644
--- a/modules/math/public/algebra.hpp
+++ b/modules/math/public/algebra.hpp
@@ -4,7 +4,6 @@
 
 namespace lt::math {
 
-
 /**
  * let...
  * a = h / w ==> for aspect ratio adjustment
diff --git a/modules/mirror/private/entrypoint/mirror.cpp b/modules/mirror/private/entrypoint/mirror.cpp
index 624df57..3254ce6 100644
--- a/modules/mirror/private/entrypoint/mirror.cpp
+++ b/modules/mirror/private/entrypoint/mirror.cpp
@@ -22,23 +22,26 @@ public:
 		setup_window_system();
 		register_systems();
 
-		m_window_system->add_event_listener([&](const surface::System::Event &event) {
-			const auto visitor = overloads {
-				[&](const lt::surface::KeyPressedEvent &event) {
-				    std::cout << "key pressed: " << event.to_string() << std::endl;
+		m_window_system->add_event_listener(
+		    m_window,
+		    [&](const surface::SurfaceComponent::Event &event) {
+			    const auto visitor = overloads {
+				    [&](const lt::surface::KeyPressedEvent &event) {
+				        std::cout << "key pressed: " << event.to_string() << std::endl;
 
-				    if (event.get_key() == 81)
-				    {
-					    unregister_system(m_window_system);
-					    log_inf("Quitting...");
-				    }
-				    return true;
-				},
-				[](const auto &) { return false; },
-			};
+				        if (event.get_key() == 81)
+				        {
+					        unregister_system(m_window_system);
+					        log_inf("Quitting...");
+				        }
+				        return true;
+				    },
+				    [](const auto &) { return false; },
+			    };
 
-			return std::visit(visitor, event);
-		});
+			    return std::visit(visitor, event);
+		    }
+		);
 	}
 
 	void setup_window_system()
diff --git a/modules/surface/CMakeLists.txt b/modules/surface/CMakeLists.txt
index 9ec4c27..30e9f5e 100644
--- a/modules/surface/CMakeLists.txt
+++ b/modules/surface/CMakeLists.txt
@@ -1,5 +1,5 @@
 if (NOT WIN32)
-    add_library_module(surface system.cpp linux/system.cpp)
+    add_library_module(surface linux/system.cpp)
 else()
 endif()
 
@@ -11,3 +11,6 @@ target_link_libraries(surface PUBLIC
     logger 
     lt_debug
 )
+
+add_test_module(surface system.test.cpp)
+target_link_libraries(surface_tests PRIVATE glfw)
diff --git a/modules/surface/private/linux/system.cpp b/modules/surface/private/linux/system.cpp
index 2e8e315..542bb9e 100644
--- a/modules/surface/private/linux/system.cpp
+++ b/modules/surface/private/linux/system.cpp
@@ -1,11 +1,13 @@
+#define GLFW_EXPOSE_NATIVE_X11
 #include <GLFW/glfw3.h>
+#include <GLFW/glfw3native.h>
 #include <surface/system.hpp>
 
 namespace lt::surface {
 
-void handle_event(GLFWwindow *window, const System::Event &event)
+void handle_event(GLFWwindow *window, const SurfaceComponent::Event &event)
 {
-	auto &callbacks = *static_cast<std::vector<System::EventCallback> *>(
+	auto &callbacks = *static_cast<std::vector<SurfaceComponent::EventCallback> *>(
 	    glfwGetWindowUserPointer(window)
 	);
 
@@ -90,6 +92,50 @@ void bind_glfw_events(GLFWwindow *handle)
 	});
 }
 
+System::System(Ref<ecs::Registry> registry): m_registry(std::move(registry))
+{
+	ensure(m_registry, "Failed to initialize surface system: null registry");
+	ensure(
+	    m_registry->view<SurfaceComponent>().size() == 0,
+	    "Failed to initialize surface system: registry has surface component(s)"
+	);
+
+	m_registry->get_entt_registry()
+	    .on_construct<SurfaceComponent>()
+	    .connect<&System::on_surface_construct>(this);
+
+	m_registry->get_entt_registry()
+	    .on_update<SurfaceComponent>()
+	    .connect<&System::on_surface_update>(this);
+
+	m_registry->get_entt_registry()
+	    .on_destroy<SurfaceComponent>()
+	    .connect<&System::on_surface_destroy>(this);
+}
+
+System::~System()
+{
+	m_registry->get_entt_registry()
+	    .on_construct<SurfaceComponent>()
+	    .disconnect<&System::on_surface_construct>(this);
+
+	m_registry->get_entt_registry()
+	    .on_update<SurfaceComponent>()
+	    .connect<&System::on_surface_update>(this);
+
+	m_registry->get_entt_registry()
+	    .on_destroy<SurfaceComponent>()
+	    .disconnect<&System::on_surface_destroy>(this);
+
+
+	m_registry->view<SurfaceComponent>().each([&](const entt::entity entity, SurfaceComponent &) {
+		std::cout << "REMOVED SURFACE COMPONENT ON DESTRUCTION" << std::endl;
+		m_registry->get_entt_registry().remove<SurfaceComponent>(entity);
+	});
+
+	glfwTerminate();
+}
+
 void System::on_surface_construct(entt::registry &registry, entt::entity entity)
 {
 	ensure(glfwInit(), "Failed to initialize 'glfw'");
@@ -111,10 +157,17 @@ void System::on_surface_construct(entt::registry &registry, entt::entity entity)
 	);
 	ensure(surface.m_glfw_handle, "Failed to create 'GLFWwindow'");
 
-	glfwSetWindowUserPointer(surface.m_glfw_handle, &m_event_callbacks);
+	glfwSetWindowUserPointer(surface.m_glfw_handle, &surface.m_event_callbacks);
+	surface.m_native_handle = glfwGetX11Window(surface.m_glfw_handle);
 	bind_glfw_events(surface.m_glfw_handle);
 }
 
+void System::on_surface_update(entt::registry &registry, entt::entity entity)
+{
+	auto &surface = registry.get<SurfaceComponent>(entity);
+	glfwSetWindowUserPointer(surface.m_glfw_handle, &surface.m_event_callbacks);
+}
+
 void System::on_surface_destroy(entt::registry &registry, entt::entity entity)
 {
 	auto &surface = registry.get<SurfaceComponent>(entity);
@@ -170,29 +223,17 @@ void System::set_visibility(ecs::Entity surface_entity, bool visible)
 	}
 }
 
+void System::add_event_listener(
+    ecs::Entity surface_entity,
+    SurfaceComponent::EventCallback callback
+)
+{
+	auto &surface = surface_entity.get_component<SurfaceComponent>();
+	surface.m_event_callbacks.emplace_back(std::move(callback));
+}
+
 } // namespace lt::surface
 
 namespace lt {
 
-// void System::on_event(const Event &event)
-// {
-// 	switch (event.get_event_type())
-// 	{
-// 	/* closed */
-// 	case EventType::WindowClosed: b_Closed = true; break;
-//
-// 	/* resized */
-// 	case EventType::WindowResized:
-// 		on_surface_resize(dynamic_cast<const WindowResizedEvent &>(event));
-// 		break;
-//
-// 	default: break;
-// 	}
-// }
-//
-// void System::on_surface_resize(const WindowResizedEvent &event)
-// {
-// 	m_properties.size = event.get_size();
-// }
-
 } // namespace lt
diff --git a/modules/surface/private/system.cpp b/modules/surface/private/system.cpp
deleted file mode 100644
index 56fc395..0000000
--- a/modules/surface/private/system.cpp
+++ /dev/null
@@ -1,27 +0,0 @@
-#include <surface/system.hpp>
-
-namespace lt::surface {
-
-System::System(Ref<ecs::Registry> registry): m_registry(std::move(registry))
-{
-	m_registry->get_entt_registry()
-	    .on_construct<SurfaceComponent>()
-	    .connect<&System::on_surface_construct>(this);
-
-	m_registry->get_entt_registry()
-	    .on_destroy<SurfaceComponent>()
-	    .connect<&System::on_surface_destroy>(this);
-}
-
-System::~System()
-{
-	m_registry->get_entt_registry()
-	    .on_construct<SurfaceComponent>()
-	    .disconnect<&System::on_surface_construct>(this);
-
-	m_registry->get_entt_registry()
-	    .on_destroy<SurfaceComponent>()
-	    .disconnect<&System::on_surface_destroy>(this);
-}
-
-} // namespace lt::surface
diff --git a/modules/surface/private/system.test.cpp b/modules/surface/private/system.test.cpp
index e69de29..31cdcbd 100644
--- a/modules/surface/private/system.test.cpp
+++ b/modules/surface/private/system.test.cpp
@@ -0,0 +1,151 @@
+#include <surface/system.hpp>
+#include <test/test.hpp>
+
+using namespace lt;
+using std::ignore;
+using surface::SurfaceComponent;
+using surface::System;
+using test::Case;
+using test::expect_eq;
+using test::expect_ne;
+using test::expect_not_nullptr;
+using test::expect_throw;
+using test::Suite;
+
+constexpr auto title = "TestWindow";
+constexpr auto width = 800u;
+constexpr auto height = 600u;
+constexpr auto vsync = true;
+constexpr auto visible = false;
+
+class Fixture
+{
+public:
+	[[nodiscard]] auto registry() -> Ref<ecs::Registry>
+	{
+		return m_registry;
+	}
+
+	auto add_surface_component() -> SurfaceComponent &
+	{
+		auto entity = m_registry->create_entity("");
+		return entity.add_component<SurfaceComponent>(SurfaceComponent::CreateInfo {
+		    .title = title,
+		    .size = { width, height },
+		    .vsync = vsync,
+		    .visible = visible,
+		});
+	}
+
+	void check_values(const SurfaceComponent &component)
+	{
+		expect_ne(std::get<SurfaceComponent::X11NativeHandle>(component.get_native_handle()), 0);
+		expect_eq(component.get_size().x, width);
+		expect_eq(component.get_size().y, height);
+		expect_eq(component.get_title(), title);
+		expect_eq(component.is_vsync(), vsync);
+		expect_eq(component.is_visible(), visible);
+	}
+
+private:
+	Ref<ecs::Registry> m_registry = create_ref<ecs::Registry>();
+};
+
+Suite raii = [] {
+	Case { "happy path won't throw" } = [] {
+		auto fixture = Fixture {};
+		ignore = System { fixture.registry() };
+	};
+
+	Case { "many won't throw" } = [] {
+		auto fixture = Fixture {};
+		for (auto idx : std::views::iota(0, 100'001))
+		{
+			ignore = System { fixture.registry() };
+		}
+	};
+
+	Case { "unhappy path throws" } = [] {
+		expect_throw([] { ignore = System { {} }; });
+
+		auto fixture = Fixture {};
+		fixture.add_surface_component();
+		expect_throw([&] { ignore = System { { fixture.registry() } }; });
+	};
+
+	Case { "post construct has correct state" } = [] {
+		auto fixture = Fixture {};
+		auto system = System { fixture.registry() };
+		expect_eq(fixture.registry()->view<SurfaceComponent>()->size(), 0);
+	};
+};
+
+Suite system_events = [] {
+	Case { "on_register won't throw" } = [] {
+		auto fixture = Fixture {};
+		auto system = System { fixture.registry() };
+
+		system.on_register();
+		expect_eq(fixture.registry()->view<SurfaceComponent>().size(), 0);
+	};
+
+	Case { "on_unregister won't throw" } = [] {
+		auto fixture = Fixture {};
+		auto system = System { fixture.registry() };
+		system.on_register();
+
+		system.on_unregister();
+		expect_eq(fixture.registry()->view<SurfaceComponent>().size(), 0);
+	};
+};
+
+Suite registry_events = [] {
+	Case { "on_construct<SurfaceComponent> initializes component" } = [] {
+		auto fixture = Fixture {};
+		auto system = System { fixture.registry() };
+
+		const auto &component = fixture.add_surface_component();
+		expect_eq(fixture.registry()->view<SurfaceComponent>().size(), 1);
+		fixture.check_values(component);
+	};
+
+	Case { "on_destrroy<SurfaceComponent> cleans up component" } = [] {
+		auto fixture = Fixture {};
+		auto system = create_scope<System>(fixture.registry());
+
+		const auto &component = fixture.add_surface_component();
+		expect_eq(fixture.registry()->view<SurfaceComponent>().size(), 1);
+		fixture.check_values(component);
+
+		system.reset();
+		expect_eq(fixture.registry()->view<SurfaceComponent>().size(), 0);
+	};
+};
+
+Suite tick = [] {
+	Case { "ticking on empty registry won't throw" } = [] {
+		auto fixture = Fixture {};
+		System { fixture.registry() }.tick();
+	};
+
+	Case { "ticking on non-empty registry won't throw" } = [] {
+		auto fixture = Fixture {};
+		auto system = System { fixture.registry() };
+
+		fixture.add_surface_component();
+		system.tick();
+	};
+
+	Case { "ticking on chaotic registry won't throw" } = [] {
+	}
+};
+
+Suite property_setters = [] {
+
+};
+
+Suite listeners = [] {
+};
+
+Suite fuzzy = [] {
+};
diff --git a/modules/surface/public/components.hpp b/modules/surface/public/components.hpp
index dba6b6e..798edab 100644
--- a/modules/surface/public/components.hpp
+++ b/modules/surface/public/components.hpp
@@ -1,16 +1,52 @@
 #pragma once
 
 #include <math/vec2.hpp>
+#include <surface/events/keyboard.hpp>
+#include <surface/events/mouse.hpp>
+#include <surface/events/surface.hpp>
+#include <variant>
 
 struct GLFWwindow;
 
 namespace lt::surface {
 
+/** Represents a platform's surface (eg. a Window).
+ *
+ * @note Read-only component, should only be modified through a system.
+ */
 class SurfaceComponent
 {
 public:
 	friend class System;
 
+	using Event = std::variant<
+	    // surface events
+	    ClosedEvent,
+	    MovedEvent,
+	    ResizedEvent,
+	    LostFocusEvent,
+	    GainFocusEvent,
+
+	    // keyboard events
+	    KeyPressedEvent,
+	    KeyRepeatEvent,
+	    KeyReleasedEvent,
+	    KeySetCharEvent,
+
+	    // mouse events
+	    MouseMovedEvent,
+	    WheelScrolledEvent,
+	    ButtonPressedEvent,
+	    ButtonReleasedEvent>;
+
+	using EventCallback = std::function<bool(const Event &)>;
+
+	using WindowsNativeHandle = void *;
+
+	using X11NativeHandle = unsigned long;
+
+	using NativeHandle = std::variant<WindowsNativeHandle, X11NativeHandle>;
+
 	struct CreateInfo
 	{
 		std::string_view title;
@@ -50,17 +86,17 @@ public:
 		return m_visible;
 	}
 
-	[[nodiscard]] auto get_native_handle() const -> void *
+	[[nodiscard]] auto get_native_handle() const -> NativeHandle
 	{
 		return m_native_handle;
 	}
 
+private:
 	[[nodiscard]] auto get_glfw_handle() const -> GLFWwindow *
 	{
 		return m_glfw_handle;
 	}
 
-private:
 	std::string_view m_title;
 
 	math::uvec2 m_size;
@@ -69,9 +105,11 @@ private:
 
 	bool m_visible;
 
-	void *m_native_handle {};
+	NativeHandle m_native_handle;
 
 	GLFWwindow *m_glfw_handle {};
+
+	std::vector<EventCallback> m_event_callbacks;
 };
 
 } // namespace lt::surface
diff --git a/modules/surface/public/system.hpp b/modules/surface/public/system.hpp
index 711a6da..b7709ab 100644
--- a/modules/surface/public/system.hpp
+++ b/modules/surface/public/system.hpp
@@ -4,38 +4,13 @@
 #include <ecs/entity.hpp>
 #include <ecs/scene.hpp>
 #include <surface/components.hpp>
-#include <surface/events/keyboard.hpp>
-#include <surface/events/mouse.hpp>
-#include <surface/events/surface.hpp>
 
 namespace lt::surface {
 
 class System: public app::ISystem
 {
 public:
-	using Event = std::variant<
-	    // surface events
-	    ClosedEvent,
-	    MovedEvent,
-	    ResizedEvent,
-	    LostFocusEvent,
-	    GainFocusEvent,
-
-	    // keyboard events
-	    KeyPressedEvent,
-	    KeyRepeatEvent,
-	    KeyReleasedEvent,
-	    KeySetCharEvent,
-
-	    // mouse events
-	    MouseMovedEvent,
-	    WheelScrolledEvent,
-	    ButtonPressedEvent,
-	    ButtonReleasedEvent>;
-
-	using EventCallback = std::function<bool(const Event &)>;
-
-	System(Ref<ecs::Registry> registry);
+	[[nodiscard]] System(Ref<ecs::Registry> registry);
 
 	~System() override;
 
@@ -47,7 +22,11 @@ public:
 
 	auto operator=(const System &) -> System & = delete;
 
-	void init() override
+	void on_register() override
+	{
+	}
+
+	void on_unregister() override
 	{
 	}
 
@@ -61,19 +40,16 @@ public:
 
 	void set_visibility(ecs::Entity surface_entity, bool visible);
 
-	void add_event_listener(EventCallback callback)
-	{
-		m_event_callbacks.emplace_back(std::move(callback));
-	}
+	void add_event_listener(ecs::Entity surface_entity, SurfaceComponent::EventCallback callback);
 
 private:
 	void on_surface_construct(entt::registry &registry, entt::entity entity);
 
+	void on_surface_update(entt::registry &registry, entt::entity entity);
+
 	void on_surface_destroy(entt::registry &registry, entt::entity entity);
 
 	Ref<ecs::Registry> m_registry;
-
-	std::vector<EventCallback> m_event_callbacks;
 };
 
 
diff --git a/modules/test/public/expects.hpp b/modules/test/public/expects.hpp
index ef342d1..825de25 100644
--- a/modules/test/public/expects.hpp
+++ b/modules/test/public/expects.hpp
@@ -140,6 +140,27 @@ constexpr void expect_false(
 	}
 }
 
+constexpr void expect_not_nullptr(
+    auto *pointer,
+    std::source_location source_location = std::source_location::current()
+)
+{
+	if (pointer == nullptr)
+	{
+		throw std::runtime_error {
+			std::format(
+			    "Failed true expectation:\n"
+			    "\tactual: nullptr\n"
+			    "\texpected: not nullptr\n"
+			    "\tlocation: {}:{}",
+			    source_location.file_name(),
+			    source_location.line()
+			),
+		};
+	}
+}
+
+
 constexpr void expect_le(
     Testable auto lhs,
     Testable auto rhs,
diff --git a/modules/test/public/test.hpp b/modules/test/public/test.hpp
index ce7ec18..92f7c18 100644
--- a/modules/test/public/test.hpp
+++ b/modules/test/public/test.hpp
@@ -84,7 +84,8 @@ struct Case
 {
 	auto operator=(std::invocable auto test) -> void // NOLINT
 	{
-		std::cout << "Running... " << name;
+		std::cout << "[Running-----------] --> ";
+        std::cout << name << '\n';
 
 		try
 		{
@@ -92,14 +93,14 @@ struct Case
 		}
 		catch (const std::exception &exp)
 		{
-			std::cout << " --> FAIL !" << '\n';
-			std::cout << exp.what() << "\n\n";
+			std::cout << exp.what() << "\n";
+			std::cout << "[-----------FAIL !!]" << "\n\n";
 			details::Registry::increment_failed_count();
 			return; // TODO(Light): Should we run the remaining tests after a failure?
 		}
 
 		details::Registry::increment_passed_count();
-		std::cout << " --> SUCCESS :D" << "\n";
+		std::cout << "[--------SUCCESS :D]" << "\n\n";
 	}
 
 	std::string_view name;