8 files changed, 883 insertions, 1 deletions

diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index 49c8151..dc985a3 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -3,5 +3,10 @@ target_sources(test_main PUBLIC
 	PhysicsTest.cpp
 	ScriptTest.cpp
 	ParticleTest.cpp
+	EventTest.cpp
+	ECSTest.cpp
+	SceneManagerTest.cpp
+	ValueBrokerTest.cpp
+	DBTest.cpp
 )
 
diff --git a/src/test/DBTest.cpp b/src/test/DBTest.cpp
new file mode 100644
index 0000000..e80814c
--- /dev/null
+++ b/src/test/DBTest.cpp
@@ -0,0 +1,28 @@
+#include <crepe/facade/DB.h>
+#include <gtest/gtest.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class DBTest : public Test {
+public:
+	DB db;
+};
+
+TEST_F(DBTest, ReadWrite) {
+	db.set("foo", "bar");
+	EXPECT_EQ(db.get("foo"), "bar");
+}
+
+TEST_F(DBTest, Nonexistant) {
+	EXPECT_THROW(db.get("foo"), std::out_of_range);
+	db.set("foo", "bar");
+	EXPECT_NO_THROW(db.get("foo"));
+}
+
+TEST_F(DBTest, Has) {
+	EXPECT_EQ(db.has("foo"), false);
+	db.set("foo", "bar");
+	EXPECT_EQ(db.has("foo"), true);
+}
diff --git a/src/test/ECSTest.cpp b/src/test/ECSTest.cpp
new file mode 100644
index 0000000..d5a5826
--- /dev/null
+++ b/src/test/ECSTest.cpp
@@ -0,0 +1,236 @@
+#include <gtest/gtest.h>
+
+#define protected public
+
+#include <crepe/ComponentManager.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/Metadata.h>
+#include <crepe/api/Transform.h>
+#include <crepe/api/Vector2.h>
+
+using namespace std;
+using namespace crepe;
+
+class ECSTest : public ::testing::Test {
+public:
+	ComponentManager mgr{};
+};
+
+TEST_F(ECSTest, createGameObject) {
+	GameObject obj = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+
+	vector<reference_wrapper<Metadata>> metadata = mgr.get_components_by_type<Metadata>();
+	vector<reference_wrapper<Transform>> transform = mgr.get_components_by_type<Transform>();
+
+	EXPECT_EQ(metadata.size(), 1);
+	EXPECT_EQ(transform.size(), 1);
+
+	EXPECT_EQ(metadata[0].get().name, "body");
+	EXPECT_EQ(metadata[0].get().tag, "person");
+	EXPECT_EQ(metadata[0].get().parent, -1);
+	EXPECT_EQ(metadata[0].get().children.size(), 0);
+
+	EXPECT_EQ(transform[0].get().position.x, 0);
+	EXPECT_EQ(transform[0].get().position.y, 0);
+	EXPECT_EQ(transform[0].get().rotation, 0);
+	EXPECT_EQ(transform[0].get().scale, 1);
+}
+
+TEST_F(ECSTest, deleteAllGameObjects) {
+	GameObject obj0 = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+	GameObject obj1 = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+
+	mgr.delete_all_components();
+
+	vector<reference_wrapper<Metadata>> metadata = mgr.get_components_by_type<Metadata>();
+	vector<reference_wrapper<Transform>> transform = mgr.get_components_by_type<Transform>();
+
+	EXPECT_EQ(metadata.size(), 0);
+	EXPECT_EQ(transform.size(), 0);
+
+	GameObject obj2 = mgr.new_object("body2", "person2", Vector2{1, 0}, 5, 1);
+
+	metadata = mgr.get_components_by_type<Metadata>();
+	transform = mgr.get_components_by_type<Transform>();
+
+	EXPECT_EQ(metadata.size(), 1);
+	EXPECT_EQ(transform.size(), 1);
+
+	EXPECT_EQ(metadata[0].get().game_object_id, 0);
+	EXPECT_EQ(metadata[0].get().name, "body2");
+	EXPECT_EQ(metadata[0].get().tag, "person2");
+	EXPECT_EQ(metadata[0].get().parent, -1);
+	EXPECT_EQ(metadata[0].get().children.size(), 0);
+
+	EXPECT_EQ(transform[0].get().game_object_id, 0);
+	EXPECT_EQ(transform[0].get().position.x, 1);
+	EXPECT_EQ(transform[0].get().position.y, 0);
+	EXPECT_EQ(transform[0].get().rotation, 5);
+	EXPECT_EQ(transform[0].get().scale, 1);
+}
+
+TEST_F(ECSTest, deleteGameObject) {
+	GameObject obj0 = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+	GameObject obj1 = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+
+	mgr.delete_all_components_of_id(0);
+
+	vector<reference_wrapper<Metadata>> metadata = mgr.get_components_by_type<Metadata>();
+	vector<reference_wrapper<Transform>> transform = mgr.get_components_by_type<Transform>();
+
+	EXPECT_EQ(metadata.size(), 1);
+	EXPECT_EQ(transform.size(), 1);
+
+	EXPECT_EQ(metadata[0].get().game_object_id, 1);
+	EXPECT_EQ(metadata[0].get().name, "body");
+	EXPECT_EQ(metadata[0].get().tag, "person");
+	EXPECT_EQ(metadata[0].get().parent, -1);
+	EXPECT_EQ(metadata[0].get().children.size(), 0);
+
+	EXPECT_EQ(transform[0].get().game_object_id, 1);
+	EXPECT_EQ(transform[0].get().position.x, 0);
+	EXPECT_EQ(transform[0].get().position.y, 0);
+	EXPECT_EQ(transform[0].get().rotation, 0);
+	EXPECT_EQ(transform[0].get().scale, 1);
+}
+
+TEST_F(ECSTest, manyGameObjects) {
+	for (int i = 0; i < 5000; i++) {
+		GameObject obj = mgr.new_object("body", "person", Vector2{0, 0}, 0, i);
+	}
+
+	vector<reference_wrapper<Metadata>> metadata = mgr.get_components_by_type<Metadata>();
+	vector<reference_wrapper<Transform>> transform = mgr.get_components_by_type<Transform>();
+
+	EXPECT_EQ(metadata.size(), 5000);
+	EXPECT_EQ(transform.size(), 5000);
+	for (int i = 0; i < 5000; i++) {
+		EXPECT_EQ(metadata[i].get().game_object_id, i);
+		EXPECT_EQ(metadata[i].get().name, "body");
+		EXPECT_EQ(metadata[i].get().tag, "person");
+		EXPECT_EQ(metadata[i].get().parent, -1);
+		EXPECT_EQ(metadata[i].get().children.size(), 0);
+
+		EXPECT_EQ(transform[i].get().game_object_id, i);
+		EXPECT_EQ(transform[i].get().position.x, 0);
+		EXPECT_EQ(transform[i].get().position.y, 0);
+		EXPECT_EQ(transform[i].get().rotation, 0);
+		EXPECT_EQ(transform[i].get().scale, i);
+	}
+
+	mgr.delete_components<Metadata>();
+
+	metadata = mgr.get_components_by_type<Metadata>();
+	transform = mgr.get_components_by_type<Transform>();
+
+	EXPECT_EQ(metadata.size(), 0);
+	EXPECT_EQ(transform.size(), 5000);
+
+	for (int i = 0; i < 10000 - 5000; i++) {
+		string tag = "person" + to_string(i);
+		GameObject obj = mgr.new_object("body", tag, Vector2{0, 0}, i, 0);
+	}
+
+	metadata = mgr.get_components_by_type<Metadata>();
+	transform = mgr.get_components_by_type<Transform>();
+
+	EXPECT_EQ(metadata.size(), 10000 - 5000);
+	EXPECT_EQ(transform.size(), 10000);
+}
+
+TEST_F(ECSTest, getComponentsByID) {
+	GameObject obj0 = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+	GameObject obj1 = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+
+	vector<reference_wrapper<Metadata>> metadata = mgr.get_components_by_id<Metadata>(0);
+	vector<reference_wrapper<Transform>> transform = mgr.get_components_by_id<Transform>(1);
+
+	EXPECT_EQ(metadata.size(), 1);
+	EXPECT_EQ(transform.size(), 1);
+
+	EXPECT_EQ(metadata[0].get().game_object_id, 0);
+	EXPECT_EQ(metadata[0].get().name, "body");
+	EXPECT_EQ(metadata[0].get().tag, "person");
+	EXPECT_EQ(metadata[0].get().parent, -1);
+	EXPECT_EQ(metadata[0].get().children.size(), 0);
+
+	EXPECT_EQ(transform[0].get().game_object_id, 1);
+	EXPECT_EQ(transform[0].get().position.x, 0);
+	EXPECT_EQ(transform[0].get().position.y, 0);
+	EXPECT_EQ(transform[0].get().rotation, 0);
+	EXPECT_EQ(transform[0].get().scale, 1);
+}
+
+TEST_F(ECSTest, tooMuchComponents) {
+	try {
+		GameObject obj0 = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+		obj0.add_component<Transform>(Vector2{10, 10}, 0, 1);
+	} catch (const exception & e) {
+		EXPECT_EQ(e.what(),
+				  string("Exceeded maximum number of instances for this component type"));
+	}
+
+	try {
+		GameObject obj1 = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+		obj1.add_component<Metadata>("body", "person");
+	} catch (const exception & e) {
+		EXPECT_EQ(e.what(),
+				  string("Exceeded maximum number of instances for this component type"));
+	}
+
+	vector<reference_wrapper<Metadata>> metadata = mgr.get_components_by_type<Metadata>();
+
+	EXPECT_EQ(metadata.size(), 2);
+	EXPECT_EQ(metadata[0].get().name, "body");
+	EXPECT_EQ(metadata[1].get().name, "body");
+}
+
+TEST_F(ECSTest, partentChild) {
+	{
+		GameObject body = mgr.new_object("body", "person", Vector2{0, 0}, 0, 1);
+		GameObject right_leg = mgr.new_object("rightLeg", "person", Vector2{1, 1}, 0, 1);
+		GameObject left_leg = mgr.new_object("leftLeg", "person", Vector2{1, 1}, 0, 1);
+		GameObject right_foot = mgr.new_object("rightFoot", "person", Vector2{2, 2}, 0, 1);
+		GameObject left_foot = mgr.new_object("leftFoot", "person", Vector2{2, 2}, 0, 1);
+
+		// Set the parent of each GameObject
+		right_foot.set_parent(right_leg);
+		left_foot.set_parent(left_leg);
+		right_leg.set_parent(body);
+		left_leg.set_parent(body);
+	}
+
+	// Get the Metadata and Transform components of each GameObject
+	vector<reference_wrapper<Metadata>> metadata = mgr.get_components_by_type<Metadata>();
+
+	// Check IDs
+	EXPECT_EQ(metadata[0].get().game_object_id, 0);
+	EXPECT_EQ(metadata[1].get().game_object_id, 1);
+	EXPECT_EQ(metadata[2].get().game_object_id, 2);
+	EXPECT_EQ(metadata[3].get().game_object_id, 3);
+	EXPECT_EQ(metadata[4].get().game_object_id, 4);
+
+	// Check the parent-child relationships
+	EXPECT_EQ(metadata[0].get().name, "body");
+	EXPECT_EQ(metadata[1].get().name, "rightLeg");
+	EXPECT_EQ(metadata[2].get().name, "leftLeg");
+	EXPECT_EQ(metadata[3].get().name, "rightFoot");
+	EXPECT_EQ(metadata[4].get().name, "leftFoot");
+
+	EXPECT_EQ(metadata[0].get().parent, -1);
+	EXPECT_EQ(metadata[1].get().parent, 0);
+	EXPECT_EQ(metadata[2].get().parent, 0);
+	EXPECT_EQ(metadata[3].get().parent, 1);
+	EXPECT_EQ(metadata[4].get().parent, 2);
+
+	EXPECT_EQ(metadata[0].get().children.size(), 2);
+	EXPECT_EQ(metadata[1].get().children.size(), 1);
+	EXPECT_EQ(metadata[2].get().children.size(), 1);
+	EXPECT_EQ(metadata[3].get().children.size(), 0);
+	EXPECT_EQ(metadata[4].get().children.size(), 0);
+
+	EXPECT_EQ(metadata[0].get().children[0], 1);
+	EXPECT_EQ(metadata[0].get().children[1], 2);
+	EXPECT_EQ(metadata[1].get().children[0], 3);
+	EXPECT_EQ(metadata[2].get().children[0], 4);
+}
diff --git a/src/test/EventTest.cpp b/src/test/EventTest.cpp
new file mode 100644
index 0000000..b0e6c9c
--- /dev/null
+++ b/src/test/EventTest.cpp
@@ -0,0 +1,254 @@
+
+#include "api/Event.h"
+#include "api/EventManager.h"
+#include "api/IKeyListener.h"
+#include "api/IMouseListener.h"
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+using namespace std;
+using namespace std::chrono_literals;
+using namespace crepe;
+
+class EventManagerTest : public ::testing::Test {
+protected:
+	void SetUp() override {
+		// Clear any existing subscriptions or events before each test
+		EventManager::get_instance().clear();
+	}
+
+	void TearDown() override {
+		// Ensure cleanup after each test
+		EventManager::get_instance().clear();
+	}
+};
+class MockKeyListener : public IKeyListener {
+public:
+	MOCK_METHOD(bool, on_key_pressed, (const KeyPressEvent & event), (override));
+	MOCK_METHOD(bool, on_key_released, (const KeyReleaseEvent & event), (override));
+};
+
+class MockMouseListener : public IMouseListener {
+public:
+	MOCK_METHOD(bool, on_mouse_clicked, (const MouseClickEvent & event), (override));
+	MOCK_METHOD(bool, on_mouse_pressed, (const MousePressEvent & event), (override));
+	MOCK_METHOD(bool, on_mouse_released, (const MouseReleaseEvent & event), (override));
+	MOCK_METHOD(bool, on_mouse_moved, (const MouseMoveEvent & event), (override));
+};
+
+TEST_F(EventManagerTest, EventSubscription) {
+	EventHandler<KeyPressEvent> key_handler = [](const KeyPressEvent & e) {
+		std::cout << "Key Event Triggered" << std::endl;
+		return true;
+	};
+
+	// Subscribe to KeyPressEvent
+	EventManager::get_instance().subscribe<KeyPressEvent>(key_handler, 1);
+
+	// Verify subscription (not directly verifiable; test by triggering event)
+
+	EventManager::get_instance().trigger_event<KeyPressEvent>(
+		KeyPressEvent{
+			.repeat = true,
+			.key = Keycode::A,
+		},
+		1);
+	EventManager::get_instance().trigger_event<KeyPressEvent>(
+		KeyPressEvent{
+			.repeat = true,
+			.key = Keycode::A,
+
+		},
+		EventManager::CHANNEL_ALL);
+}
+TEST_F(EventManagerTest, EventManagerTest_trigger_all_channels) {
+	bool triggered = false;
+
+	EventHandler<MouseClickEvent> mouse_handler = [&](const MouseClickEvent & e) {
+		triggered = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false;
+	};
+	EventManager::get_instance().subscribe<MouseClickEvent>(mouse_handler,
+															EventManager::CHANNEL_ALL);
+
+	MouseClickEvent click_event{
+		.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE};
+	EventManager::get_instance().trigger_event<MouseClickEvent>(click_event,
+																EventManager::CHANNEL_ALL);
+
+	EXPECT_TRUE(triggered);
+}
+TEST_F(EventManagerTest, EventManagerTest_trigger_one_channel) {
+	bool triggered = false;
+	int test_channel = 1;
+	EventHandler<MouseClickEvent> mouse_handler = [&](const MouseClickEvent & e) {
+		triggered = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false;
+	};
+	EventManager::get_instance().subscribe<MouseClickEvent>(mouse_handler, test_channel);
+
+	MouseClickEvent click_event{
+		.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE};
+	EventManager::get_instance().trigger_event<MouseClickEvent>(click_event,
+																EventManager::CHANNEL_ALL);
+
+	EXPECT_FALSE(triggered);
+	EventManager::get_instance().trigger_event<MouseClickEvent>(click_event, test_channel);
+}
+
+TEST_F(EventManagerTest, EventManagerTest_callback_propagation) {
+	EventManager & event_manager = EventManager::get_instance();
+
+	// Flags to track handler calls
+	bool triggered_true = false;
+	bool triggered_false = false;
+
+	// Handlers
+	EventHandler<MouseClickEvent> mouse_handler_true = [&](const MouseClickEvent & e) {
+		triggered_true = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return true; // Stops propagation
+	};
+
+	EventHandler<MouseClickEvent> mouse_handler_false = [&](const MouseClickEvent & e) {
+		triggered_false = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+
+	// Test event
+	MouseClickEvent click_event{
+		.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE};
+	event_manager.subscribe<MouseClickEvent>(mouse_handler_true, EventManager::CHANNEL_ALL);
+	event_manager.subscribe<MouseClickEvent>(mouse_handler_false, EventManager::CHANNEL_ALL);
+
+	// Trigger event
+	event_manager.trigger_event<MouseClickEvent>(click_event, EventManager::CHANNEL_ALL);
+
+	// Check that only the true handler was triggered
+	EXPECT_TRUE(triggered_true);
+	EXPECT_FALSE(triggered_false);
+
+	// Reset and clear
+	triggered_true = false;
+	triggered_false = false;
+	event_manager.clear();
+	event_manager.subscribe<MouseClickEvent>(mouse_handler_false, EventManager::CHANNEL_ALL);
+	event_manager.subscribe<MouseClickEvent>(mouse_handler_true, EventManager::CHANNEL_ALL);
+
+	// Trigger event again
+	event_manager.trigger_event<MouseClickEvent>(click_event, EventManager::CHANNEL_ALL);
+
+	// Check that both handlers were triggered
+	EXPECT_TRUE(triggered_true);
+	EXPECT_TRUE(triggered_false);
+}
+
+TEST_F(EventManagerTest, EventManagerTest_queue_dispatch) {
+	EventManager & event_manager = EventManager::get_instance();
+	bool triggered1 = false;
+	bool triggered2 = false;
+	int test_channel = 1;
+	EventHandler<MouseClickEvent> mouse_handler1 = [&](const MouseClickEvent & e) {
+		triggered1 = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+	EventHandler<MouseClickEvent> mouse_handler2 = [&](const MouseClickEvent & e) {
+		triggered2 = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+	event_manager.subscribe<MouseClickEvent>(mouse_handler1);
+	event_manager.subscribe<MouseClickEvent>(mouse_handler2, test_channel);
+
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE});
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE},
+		test_channel);
+	event_manager.dispatch_events();
+	EXPECT_TRUE(triggered1);
+	EXPECT_TRUE(triggered2);
+}
+
+TEST_F(EventManagerTest, EventManagerTest_unsubscribe) {
+	EventManager & event_manager = EventManager::get_instance();
+
+	// Flags to track if handlers are triggered
+	bool triggered1 = false;
+	bool triggered2 = false;
+
+	// Define EventHandlers
+	EventHandler<MouseClickEvent> mouse_handler1 = [&](const MouseClickEvent & e) {
+		triggered1 = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+
+	EventHandler<MouseClickEvent> mouse_handler2 = [&](const MouseClickEvent & e) {
+		triggered2 = true;
+		EXPECT_EQ(e.mouse_x, 100);
+		EXPECT_EQ(e.mouse_y, 200);
+		EXPECT_EQ(e.button, MouseButton::LEFT_MOUSE);
+		return false; // Allows propagation
+	};
+	// Subscribe handlers
+	subscription_t handler1_id = event_manager.subscribe<MouseClickEvent>(mouse_handler1);
+	subscription_t handler2_id = event_manager.subscribe<MouseClickEvent>(mouse_handler2);
+
+	// Queue events
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE});
+
+	// Dispatch events - both handlers should be triggered
+	event_manager.dispatch_events();
+	EXPECT_TRUE(triggered1); // Handler 1 should be triggered
+	EXPECT_TRUE(triggered2); // Handler 2 should be triggered
+
+	// Reset flags
+	triggered1 = false;
+	triggered2 = false;
+
+	// Unsubscribe handler1
+	event_manager.unsubscribe(handler1_id);
+
+	// Queue the same event again
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE});
+
+	// Dispatch events - only handler 2 should be triggered, handler 1 should NOT
+	event_manager.dispatch_events();
+	EXPECT_FALSE(triggered1); // Handler 1 should NOT be triggered
+	EXPECT_TRUE(triggered2); // Handler 2 should be triggered
+
+	// Reset flags
+	triggered2 = false;
+
+	// Unsubscribe handler2
+	event_manager.unsubscribe(handler2_id);
+
+	// Queue the event again
+	event_manager.queue_event<MouseClickEvent>(
+		MouseClickEvent{.mouse_x = 100, .mouse_y = 200, .button = MouseButton::LEFT_MOUSE});
+
+	// Dispatch events - no handler should be triggered
+	event_manager.dispatch_events();
+	EXPECT_FALSE(triggered1); // Handler 1 should NOT be triggered
+	EXPECT_FALSE(triggered2); // Handler 2 should NOT be triggered
+}
diff --git a/src/test/ParticleTest.cpp b/src/test/ParticleTest.cpp
index 4e655a9..d9bbba0 100644
--- a/src/test/ParticleTest.cpp
+++ b/src/test/ParticleTest.cpp
@@ -28,7 +28,7 @@ public:
 			GameObject game_object = mgr.new_object("", "", Vector2{0, 0}, 0, 0);
 
 			Color color(0, 0, 0, 0);
-			Sprite test_sprite = game_object.add_component<Sprite>(
+			Sprite & test_sprite = game_object.add_component<Sprite>(
 				make_shared<Texture>("../asset/texture/img.png"), color,
 				FlipSettings{true, true});
 
diff --git a/src/test/RenderSystemTest.cpp b/src/test/RenderSystemTest.cpp
new file mode 100644
index 0000000..ac479d3
--- /dev/null
+++ b/src/test/RenderSystemTest.cpp
@@ -0,0 +1,174 @@
+#include "api/Camera.h"
+#include <functional>
+#include <gtest/gtest.h>
+#include <memory>
+#include <vector>
+
+#define private public
+#define protected public
+
+#include <crepe/ComponentManager.h>
+#include <crepe/api/Color.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/Sprite.h>
+#include <crepe/api/Texture.h>
+
+#include <crepe/system/RenderSystem.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class RenderSystemTest : public Test {
+public:
+	ComponentManager mgr{};
+	RenderSystem sys{mgr};
+	GameObject entity1 = this->mgr.new_object("name");
+	GameObject entity2 = this->mgr.new_object("name");
+	GameObject entity3 = this->mgr.new_object("name");
+	GameObject entity4 = this->mgr.new_object("name");
+
+	void SetUp() override {
+		auto & sprite1
+			= entity1.add_component<Sprite>(make_shared<Texture>("../asset/texture/img.png"),
+											Color(0, 0, 0, 0), FlipSettings{false, false});
+		ASSERT_NE(sprite1.sprite_image.get(), nullptr);
+		sprite1.order_in_layer = 5;
+		sprite1.sorting_in_layer = 5;
+		EXPECT_EQ(sprite1.order_in_layer, 5);
+		EXPECT_EQ(sprite1.sorting_in_layer, 5);
+		auto & sprite2
+			= entity2.add_component<Sprite>(make_shared<Texture>("../asset/texture/img.png"),
+											Color(0, 0, 0, 0), FlipSettings{false, false});
+		ASSERT_NE(sprite2.sprite_image.get(), nullptr);
+		sprite2.sorting_in_layer = 2;
+		sprite2.order_in_layer = 1;
+
+		EXPECT_EQ(sprite2.sorting_in_layer, 2);
+		EXPECT_EQ(sprite2.order_in_layer, 1);
+
+		auto & sprite3
+			= entity3.add_component<Sprite>(make_shared<Texture>("../asset/texture/img.png"),
+											Color(0, 0, 0, 0), FlipSettings{false, false});
+		ASSERT_NE(sprite3.sprite_image.get(), nullptr);
+		sprite3.sorting_in_layer = 1;
+		sprite3.order_in_layer = 2;
+
+		EXPECT_EQ(sprite3.sorting_in_layer, 1);
+		EXPECT_EQ(sprite3.order_in_layer, 2);
+
+		auto & sprite4
+			= entity4.add_component<Sprite>(make_shared<Texture>("../asset/texture/img.png"),
+											Color(0, 0, 0, 0), FlipSettings{false, false});
+		ASSERT_NE(sprite4.sprite_image.get(), nullptr);
+		sprite4.sorting_in_layer = 1;
+		sprite4.order_in_layer = 1;
+		EXPECT_EQ(sprite4.sorting_in_layer, 1);
+		EXPECT_EQ(sprite4.order_in_layer, 1);
+	}
+};
+
+TEST_F(RenderSystemTest, expected_throws) {
+	GameObject entity1 = this->mgr.new_object("NAME");
+
+	// no texture img
+	EXPECT_ANY_THROW({
+		entity1.add_component<Sprite>(make_shared<Texture>("NO_IMAGE"), Color(0, 0, 0, 0),
+									  FlipSettings{false, false});
+	});
+
+	// No camera
+	EXPECT_ANY_THROW({ this->sys.update(); });
+}
+
+TEST_F(RenderSystemTest, make_sprites) {}
+
+TEST_F(RenderSystemTest, sorting_sprites) {
+	vector<reference_wrapper<Sprite>> sprites = this->mgr.get_components_by_type<Sprite>();
+	ASSERT_EQ(sprites.size(), 4);
+
+	vector<reference_wrapper<Sprite>> sorted_sprites = this->sys.sort(sprites);
+	ASSERT_EQ(sorted_sprites.size(), 4);
+
+	// Expected order after sorting:
+	// 1. sorting_in_layer: 1, order_in_layer: 1 (entity4)
+	// 2. sorting_in_layer: 1, order_in_layer: 2 (entity3)
+	// 3. sorting_in_layer: 2, order_in_layer: 1 (entity2)
+	// 4. sorting_in_layer: 5, order_in_layer: 5 (entity1)
+
+	EXPECT_EQ(sorted_sprites[0].get().sorting_in_layer, 1);
+	EXPECT_EQ(sorted_sprites[0].get().order_in_layer, 1);
+
+	EXPECT_EQ(sorted_sprites[1].get().sorting_in_layer, 1);
+	EXPECT_EQ(sorted_sprites[1].get().order_in_layer, 2);
+
+	EXPECT_EQ(sorted_sprites[2].get().sorting_in_layer, 2);
+	EXPECT_EQ(sorted_sprites[2].get().order_in_layer, 1);
+
+	EXPECT_EQ(sorted_sprites[3].get().sorting_in_layer, 5);
+	EXPECT_EQ(sorted_sprites[3].get().order_in_layer, 5);
+
+	for (size_t i = 1; i < sorted_sprites.size(); ++i) {
+		const Sprite & prev = sorted_sprites[i - 1].get();
+		const Sprite & curr = sorted_sprites[i].get();
+
+		if (prev.sorting_in_layer == curr.sorting_in_layer) {
+			EXPECT_LE(prev.order_in_layer, curr.order_in_layer);
+		} else {
+			EXPECT_LE(prev.sorting_in_layer, curr.sorting_in_layer);
+		}
+	}
+}
+
+TEST_F(RenderSystemTest, Update) {
+	entity1.add_component<Camera>(Color::WHITE);
+	{
+		vector<reference_wrapper<Sprite>> sprites = this->mgr.get_components_by_type<Sprite>();
+		ASSERT_EQ(sprites.size(), 4);
+
+		EXPECT_EQ(sprites[0].get().game_object_id, 0);
+		EXPECT_EQ(sprites[1].get().game_object_id, 1);
+		EXPECT_EQ(sprites[2].get().game_object_id, 2);
+		EXPECT_EQ(sprites[3].get().game_object_id, 3);
+	}
+	this->sys.update();
+	{
+		vector<reference_wrapper<Sprite>> sprites = this->mgr.get_components_by_type<Sprite>();
+		ASSERT_EQ(sprites.size(), 4);
+
+		EXPECT_EQ(sprites[0].get().game_object_id, 0);
+		EXPECT_EQ(sprites[1].get().game_object_id, 1);
+		EXPECT_EQ(sprites[2].get().game_object_id, 2);
+		EXPECT_EQ(sprites[3].get().game_object_id, 3);
+	}
+}
+
+TEST_F(RenderSystemTest, Camera) {
+	{
+		auto cameras = this->mgr.get_components_by_type<Camera>();
+		EXPECT_NE(cameras.size(), 1);
+	}
+	{
+		entity1.add_component<Camera>(Color::WHITE);
+		auto cameras = this->mgr.get_components_by_type<Camera>();
+		EXPECT_EQ(cameras.size(), 1);
+	}
+
+	//TODO improve with newer version
+}
+TEST_F(RenderSystemTest, Color) {
+	entity1.add_component<Camera>(Color::WHITE);
+	auto & sprite = this->mgr.get_components_by_id<Sprite>(entity1.id).front().get();
+	ASSERT_NE(sprite.sprite_image.get(), nullptr);
+
+	sprite.color = Color::GREEN;
+	EXPECT_EQ(sprite.color.r, Color::GREEN.r);
+	EXPECT_EQ(sprite.color.g, Color::GREEN.g);
+	EXPECT_EQ(sprite.color.b, Color::GREEN.b);
+	EXPECT_EQ(sprite.color.a, Color::GREEN.a);
+	this->sys.update();
+	EXPECT_EQ(sprite.color.r, Color::GREEN.r);
+	EXPECT_EQ(sprite.color.g, Color::GREEN.g);
+	EXPECT_EQ(sprite.color.b, Color::GREEN.b);
+	EXPECT_EQ(sprite.color.a, Color::GREEN.a);
+}
diff --git a/src/test/SceneManagerTest.cpp b/src/test/SceneManagerTest.cpp
new file mode 100644
index 0000000..69e1171
--- /dev/null
+++ b/src/test/SceneManagerTest.cpp
@@ -0,0 +1,122 @@
+#include <crepe/ComponentManager.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/Metadata.h>
+#include <crepe/api/Scene.h>
+#include <crepe/api/SceneManager.h>
+#include <crepe/api/Transform.h>
+#include <crepe/api/Vector2.h>
+#include <gtest/gtest.h>
+
+using namespace std;
+using namespace crepe;
+
+class ConcreteScene1 : public Scene {
+public:
+	using Scene::Scene;
+
+	void load_scene() {
+		auto & mgr = this->component_manager;
+		GameObject object1 = mgr.new_object("scene_1", "tag_scene_1", Vector2{0, 0}, 0, 1);
+		GameObject object2 = mgr.new_object("scene_1", "tag_scene_1", Vector2{1, 0}, 0, 1);
+		GameObject object3 = mgr.new_object("scene_1", "tag_scene_1", Vector2{2, 0}, 0, 1);
+	}
+};
+
+class ConcreteScene2 : public Scene {
+public:
+	using Scene::Scene;
+
+	void load_scene() {
+		auto & mgr = this->component_manager;
+		GameObject object1 = mgr.new_object("scene_2", "tag_scene_2", Vector2{0, 0}, 0, 1);
+		GameObject object2 = mgr.new_object("scene_2", "tag_scene_2", Vector2{0, 1}, 0, 1);
+		GameObject object3 = mgr.new_object("scene_2", "tag_scene_2", Vector2{0, 2}, 0, 1);
+		GameObject object4 = mgr.new_object("scene_2", "tag_scene_2", Vector2{0, 3}, 0, 1);
+	}
+};
+
+class SceneManagerTest : public ::testing::Test {
+public:
+	ComponentManager component_mgr{};
+	SceneManager scene_mgr{component_mgr};
+};
+
+TEST_F(SceneManagerTest, loadScene) {
+	scene_mgr.add_scene<ConcreteScene1>("scene1");
+	scene_mgr.add_scene<ConcreteScene2>("scene2");
+
+	scene_mgr.load_next_scene();
+
+	vector<reference_wrapper<Metadata>> metadata
+		= component_mgr.get_components_by_type<Metadata>();
+	vector<reference_wrapper<Transform>> transform
+		= component_mgr.get_components_by_type<Transform>();
+
+	EXPECT_EQ(metadata.size(), 3);
+	EXPECT_EQ(transform.size(), 3);
+
+	EXPECT_EQ(metadata[0].get().game_object_id, 0);
+	EXPECT_EQ(metadata[0].get().name, "scene_1");
+	EXPECT_EQ(metadata[0].get().tag, "tag_scene_1");
+	EXPECT_EQ(metadata[0].get().parent, -1);
+	EXPECT_EQ(metadata[0].get().children.size(), 0);
+	EXPECT_EQ(transform[0].get().position.x, 0);
+	EXPECT_EQ(transform[0].get().position.y, 0);
+
+	EXPECT_EQ(metadata[1].get().game_object_id, 1);
+	EXPECT_EQ(metadata[1].get().name, "scene_1");
+	EXPECT_EQ(metadata[1].get().tag, "tag_scene_1");
+	EXPECT_EQ(metadata[1].get().parent, -1);
+	EXPECT_EQ(metadata[1].get().children.size(), 0);
+	EXPECT_EQ(transform[1].get().position.x, 1);
+	EXPECT_EQ(transform[1].get().position.y, 0);
+
+	EXPECT_EQ(metadata[2].get().game_object_id, 2);
+	EXPECT_EQ(metadata[2].get().name, "scene_1");
+	EXPECT_EQ(metadata[2].get().tag, "tag_scene_1");
+	EXPECT_EQ(metadata[2].get().parent, -1);
+	EXPECT_EQ(metadata[2].get().children.size(), 0);
+	EXPECT_EQ(transform[2].get().position.x, 2);
+	EXPECT_EQ(transform[2].get().position.y, 0);
+
+	scene_mgr.set_next_scene("scene2");
+	scene_mgr.load_next_scene();
+
+	metadata = component_mgr.get_components_by_type<Metadata>();
+	transform = component_mgr.get_components_by_type<Transform>();
+
+	EXPECT_EQ(metadata.size(), 4);
+	EXPECT_EQ(transform.size(), 4);
+
+	EXPECT_EQ(metadata[0].get().game_object_id, 0);
+	EXPECT_EQ(metadata[0].get().name, "scene_2");
+	EXPECT_EQ(metadata[0].get().tag, "tag_scene_2");
+	EXPECT_EQ(metadata[0].get().parent, -1);
+	EXPECT_EQ(metadata[0].get().children.size(), 0);
+	EXPECT_EQ(transform[0].get().position.x, 0);
+	EXPECT_EQ(transform[0].get().position.y, 0);
+
+	EXPECT_EQ(metadata[1].get().game_object_id, 1);
+	EXPECT_EQ(metadata[1].get().name, "scene_2");
+	EXPECT_EQ(metadata[1].get().tag, "tag_scene_2");
+	EXPECT_EQ(metadata[1].get().parent, -1);
+	EXPECT_EQ(metadata[1].get().children.size(), 0);
+	EXPECT_EQ(transform[1].get().position.x, 0);
+	EXPECT_EQ(transform[1].get().position.y, 1);
+
+	EXPECT_EQ(metadata[2].get().game_object_id, 2);
+	EXPECT_EQ(metadata[2].get().name, "scene_2");
+	EXPECT_EQ(metadata[2].get().tag, "tag_scene_2");
+	EXPECT_EQ(metadata[2].get().parent, -1);
+	EXPECT_EQ(metadata[2].get().children.size(), 0);
+	EXPECT_EQ(transform[2].get().position.x, 0);
+	EXPECT_EQ(transform[2].get().position.y, 2);
+
+	EXPECT_EQ(metadata[3].get().game_object_id, 3);
+	EXPECT_EQ(metadata[3].get().name, "scene_2");
+	EXPECT_EQ(metadata[3].get().tag, "tag_scene_2");
+	EXPECT_EQ(metadata[3].get().parent, -1);
+	EXPECT_EQ(metadata[3].get().children.size(), 0);
+	EXPECT_EQ(transform[3].get().position.x, 0);
+	EXPECT_EQ(transform[3].get().position.y, 3);
+}
diff --git a/src/test/ValueBrokerTest.cpp b/src/test/ValueBrokerTest.cpp
new file mode 100644
index 0000000..e6bb058
--- /dev/null
+++ b/src/test/ValueBrokerTest.cpp
@@ -0,0 +1,63 @@
+#include <gtest/gtest.h>
+
+#include <crepe/ValueBroker.h>
+#include <crepe/util/Proxy.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class ValueBrokerTest : public Test {
+public:
+	int read_count = 0;
+	int write_count = 0;
+	int value = 0;
+
+	ValueBroker<int> broker{
+		[this](const int & target) -> void {
+			this->write_count++;
+			this->value = target;
+		},
+		[this]() -> const int & {
+			this->read_count++;
+			return this->value;
+		},
+	};
+	Proxy<int> proxy{broker};
+
+	void SetUp() override {
+		ASSERT_EQ(read_count, 0);
+		ASSERT_EQ(write_count, 0);
+	}
+};
+
+TEST_F(ValueBrokerTest, BrokerWrite) {
+	broker.set(0);
+	EXPECT_EQ(read_count, 0);
+	EXPECT_EQ(write_count, 1);
+}
+
+TEST_F(ValueBrokerTest, BrokerRead) {
+	broker.get();
+	EXPECT_EQ(read_count, 1);
+	EXPECT_EQ(write_count, 0);
+}
+
+TEST_F(ValueBrokerTest, ProxyWrite) {
+	proxy = 0;
+	EXPECT_EQ(read_count, 0);
+	EXPECT_EQ(write_count, 1);
+}
+
+void dummy(int) {}
+TEST_F(ValueBrokerTest, ProxyRead) {
+	dummy(proxy);
+	EXPECT_EQ(read_count, 1);
+	EXPECT_EQ(write_count, 0);
+}
+
+TEST_F(ValueBrokerTest, ProxyReadWrite) {
+	proxy = proxy;
+	ASSERT_EQ(read_count, 1);
+	ASSERT_EQ(write_count, 1);
+}