add script unit tests + major refactoring

50 files changed, 338 insertions, 161 deletions

diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index e4922df..445a8b2 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -38,6 +38,5 @@ install(
 
 target_link_libraries(test_main
 	PRIVATE gtest
-	PRIVATE gtest_main
 	PUBLIC crepe
 )
diff --git a/src/crepe/Asset.cpp b/src/crepe/Asset.cpp
index 8a2a11c..3d4df53 100644
--- a/src/crepe/Asset.cpp
+++ b/src/crepe/Asset.cpp
@@ -1,16 +1,20 @@
 #include <filesystem>
 
 #include "Asset.h"
+#include "Exception.h"
 
 using namespace crepe;
+using namespace std;
 
-Asset::Asset(const std::string & src) {
-	// FIXME: restore this
-	// this->src = std::filesystem::canonical(src);
-	this->src = src;
-	this->file = std::ifstream(this->src, std::ios::in | std::ios::binary);
+Asset::Asset(const string & src) : src(src) {
+	try {
+		this->src = filesystem::canonical(src);
+	} catch (filesystem::filesystem_error & e) {
+		throw Exception("Asset error: %s", e.what());
+	}
+	this->file = ifstream(this->src, ios::in | ios::binary);
 }
 
-const std::istream & Asset::read() { return this->file; }
+const istream & Asset::read() { return this->file; }
 
-const char * Asset::canonical() { return this->src.c_str(); }
+const char * Asset::canonical() const { return this->src.c_str(); }
diff --git a/src/crepe/Asset.h b/src/crepe/Asset.h
index 0cb5834..d4e4ba1 100644
--- a/src/crepe/Asset.h
+++ b/src/crepe/Asset.h
@@ -23,7 +23,7 @@ public:
 	//! Get an input stream to the contents of this resource
 	const std::istream & read();
 	//! Get the canonical path to this resource
-	const char * canonical();
+	const char * canonical() const;
 
 private:
 	std::string src;
diff --git a/src/crepe/Collider.cpp b/src/crepe/Collider.cpp
index bbec488..b408609 100644
--- a/src/crepe/Collider.cpp
+++ b/src/crepe/Collider.cpp
@@ -2,4 +2,3 @@
 
 using namespace crepe;
 
-Collider::Collider(game_object_id_t id) : Component(id) {}
diff --git a/src/crepe/Collider.h b/src/crepe/Collider.h
index 827f83d..a1e9095 100644
--- a/src/crepe/Collider.h
+++ b/src/crepe/Collider.h
@@ -6,7 +6,7 @@ namespace crepe {
 
 class Collider : public Component {
 public:
-	Collider(game_object_id_t id);
+	using Component::Component;
 
 	int size;
 };
diff --git a/src/crepe/Component.cpp b/src/crepe/Component.cpp
index 73c2d07..c133739 100644
--- a/src/crepe/Component.cpp
+++ b/src/crepe/Component.cpp
@@ -1,6 +1,6 @@
 #include "Component.h"
-#include "types.h"
 
 using namespace crepe;
 
-Component::Component(game_object_id_t id) : game_object_id(id) {}
+Component::Component(const Data & data) : data(data) {}
+
diff --git a/src/crepe/Component.h b/src/crepe/Component.h
index 0fe60b2..c6d72df 100644
--- a/src/crepe/Component.h
+++ b/src/crepe/Component.h
@@ -2,8 +2,6 @@
 
 #include "types.h"
 
-#include <cstdint>
-
 namespace crepe {
 
 class ComponentManager;
@@ -15,13 +13,21 @@ class ComponentManager;
  * interface for all components.
  */
 class Component {
+public:
+	struct Data {
+		//! The ID of the GameObject this component belongs to
+		const game_object_id_t id;
+		//! The manager of this component
+		ComponentManager & component_manager;
+	};
+
 protected:
-	//! Only the ComponentManager can create components
-	friend class crepe::ComponentManager;
 	/**
-	 * \param id The id of the GameObject this component belongs to
+	 * \param base Data
 	 */
-	Component(game_object_id_t id);
+	Component(const Data & base);
+	//! Only the ComponentManager can create components
+	friend class crepe::ComponentManager;
 
 public:
 	virtual ~Component() = default;
@@ -37,8 +43,7 @@ public:
 	virtual int get_instances_max() const { return -1; }
 
 public:
-	//! The id of the GameObject this component belongs to
-	const game_object_id_t game_object_id;
+	Data data;
 	//! Whether the component is active
 	bool active = true;
 };
diff --git a/src/crepe/ComponentManager.cpp b/src/crepe/ComponentManager.cpp
index 85149c8..f6acc1a 100644
--- a/src/crepe/ComponentManager.cpp
+++ b/src/crepe/ComponentManager.cpp
@@ -1,13 +1,10 @@
+#include "api/GameObject.h"
 #include "util/log.h"
 
 #include "ComponentManager.h"
 
 using namespace crepe;
-
-ComponentManager & ComponentManager::get_instance() {
-	static ComponentManager instance;
-	return instance;
-}
+using namespace std;
 
 void ComponentManager::delete_all_components_of_id(game_object_id_t id) {
 	// Loop through all the types (in the unordered_map<>)
@@ -26,5 +23,12 @@ void ComponentManager::delete_all_components() {
 }
 
 ComponentManager::ComponentManager() { dbg_trace(); }
-
 ComponentManager::~ComponentManager() { dbg_trace(); }
+
+GameObject & ComponentManager::new_object(const string & name, const string & tag, const Vector2 & position, double rotation, double scale) {
+	GameObject * object = new GameObject(*this, this->next_id, name, tag, position, rotation, scale);
+	this->objects.push_front(unique_ptr<GameObject>(object));
+	this->next_id++;
+	return *object;
+}
+
diff --git a/src/crepe/ComponentManager.h b/src/crepe/ComponentManager.h
index c8c196c..e37bc4a 100644
--- a/src/crepe/ComponentManager.h
+++ b/src/crepe/ComponentManager.h
@@ -1,15 +1,18 @@
 #pragma once
 
-#include <cstdint>
 #include <memory>
 #include <typeindex>
 #include <unordered_map>
 #include <vector>
+#include <forward_list>
 
 #include "Component.h"
+#include "api/Vector2.h"
 
 namespace crepe {
 
+class GameObject;
+
 /**
  * \brief Manages all components
  * 
@@ -18,18 +21,10 @@ namespace crepe {
  */
 class ComponentManager {
 public:
-	/**
-	 * \brief Get the instance of the ComponentManager
-	 * 
-	 * \return The instance of the ComponentManager
-	 */
-	static ComponentManager & get_instance();
-	ComponentManager(const ComponentManager &) = delete;
-	ComponentManager(ComponentManager &&) = delete;
-	ComponentManager & operator=(const ComponentManager &) = delete;
-	ComponentManager & operator=(ComponentManager &&) = delete;
-	~ComponentManager();
+	ComponentManager(); // dbg_trace
+	~ComponentManager(); // dbg_trace
 
+public:
 	/**
 	 * \brief Add a component to the ComponentManager
 	 * 
@@ -100,8 +95,8 @@ public:
 	template <typename T>
 	std::vector<std::reference_wrapper<T>> get_components_by_type() const;
 
-private:
-	ComponentManager();
+	// TODO: doxygen
+	GameObject & new_object(const std::string & name, const std::string & tag = "", const Vector2 & position = { 0, 0 }, double rotation = 0, double scale = 0);
 
 private:
 	/**
@@ -118,6 +113,10 @@ private:
 	std::unordered_map<std::type_index,
 					   std::vector<std::vector<std::unique_ptr<Component>>>>
 		components;
+
+	//! ID of next GameObject
+	game_object_id_t next_id = 0;
+	std::forward_list<std::unique_ptr<GameObject>> objects;
 };
 
 } // namespace crepe
diff --git a/src/crepe/ComponentManager.hpp b/src/crepe/ComponentManager.hpp
index 98efb49..89a8536 100644
--- a/src/crepe/ComponentManager.hpp
+++ b/src/crepe/ComponentManager.hpp
@@ -31,7 +31,10 @@ T & ComponentManager::add_component(game_object_id_t id, Args &&... args) {
 
 	// Create a new component of type T (arguments directly forwarded). The
 	// constructor must be called by ComponentManager.
-	T * instance_ptr = new T(id, forward<Args>(args)...);
+	T * instance_ptr = new T(Component::Data {
+		.id = id,
+		.component_manager = *this,
+	}, forward<Args>(args)...);
 	if (instance_ptr == nullptr) throw std::bad_alloc();
 
 	T & instance_ref = *instance_ptr;
diff --git a/src/crepe/Resource.h b/src/crepe/Resource.h
new file mode 100644
index 0000000..dcf3dbd
--- /dev/null
+++ b/src/crepe/Resource.h
@@ -0,0 +1,33 @@
+#pragma once
+
+#include <memory>
+
+namespace crepe {
+
+class ResourceManager;
+class Asset;
+
+/**
+ * Resource is an interface class used to represent a (deserialized) game
+ * resource (e.g. textures, sounds).
+ */
+class Resource {
+private:
+	/**
+	 * \brief Prototype pattern clone function.
+	 *
+	 * \param src Source file of new resource (abstraction for file saved on
+	 * disk)
+	 *
+	 * \returns New instance of concrete resource
+	 */
+	virtual std::unique_ptr<Resource> clone(const Asset & src) const = 0;
+	/**
+	 * The resource manager uses \c clone to create new instances of the concrete
+	 * resource class. This may be used to inherit references to classes that
+	 * would otherwise need to be implemented as singletons.
+	 */
+	friend class ResourceManager;
+};
+
+} // namespace crepe
diff --git a/src/crepe/api/Animator.cpp b/src/crepe/api/Animator.cpp
index 58fee2a..ad60981 100644
--- a/src/crepe/api/Animator.cpp
+++ b/src/crepe/api/Animator.cpp
@@ -9,8 +9,8 @@
 
 using namespace crepe;
 
-Animator::Animator(uint32_t id, Sprite & ss, int row, int col, int col_animator)
-	: Component(id),
+Animator::Animator(const Component::Data & data, Sprite & ss, int row, int col, int col_animator)
+	: Component(data),
 	  spritesheet(ss),
 	  row(row),
 	  col(col) {
diff --git a/src/crepe/api/Animator.h b/src/crepe/api/Animator.h
index def0240..f66dc1a 100644
--- a/src/crepe/api/Animator.h
+++ b/src/crepe/api/Animator.h
@@ -6,6 +6,7 @@
 #include "Sprite.h"
 
 namespace crepe {
+
 class AnimatorSystem;
 class SDLContext;
 
@@ -35,7 +36,7 @@ public:
 	 *
 	 * This constructor sets up the Animator with the given parameters, and initializes the animation system.
 	 */
-	Animator(uint32_t id, Sprite & spritesheet, int row, int col,
+	Animator(const Component::Data & data, Sprite & spritesheet, int row, int col,
 			 int col_animate);
 
 	~Animator(); // dbg_trace
diff --git a/src/crepe/api/BehaviorScript.cpp b/src/crepe/api/BehaviorScript.cpp
index e69de29..ce1cfde 100644
--- a/src/crepe/api/BehaviorScript.cpp
+++ b/src/crepe/api/BehaviorScript.cpp
@@ -0,0 +1,4 @@
+#include "BehaviorScript.h"
+
+using namespace crepe;
+
diff --git a/src/crepe/api/BehaviorScript.h b/src/crepe/api/BehaviorScript.h
index 6b1fec7..8d21a72 100644
--- a/src/crepe/api/BehaviorScript.h
+++ b/src/crepe/api/BehaviorScript.h
@@ -12,19 +12,35 @@ class Script;
 
 class BehaviorScript : public Component {
 protected:
-	friend class crepe::ComponentManager;
 	using Component::Component;
+	//! Only ComponentManager is allowed to instantiate BehaviorScript
+	friend class ComponentManager;
 
 public:
 	virtual ~BehaviorScript() = default;
 
 public:
+	/**
+	 * \brief Set the concrete script of this component
+	 *
+	 * \tparam T Concrete script type (derived from \c crepe::Script)
+	 *
+	 * \returns Reference to BehaviorScript component (`*this`)
+	 */
 	template <class T>
 	BehaviorScript & set_script();
 
 protected:
-	friend class crepe::ScriptSystem;
+	//! ScriptSystem needs direct access to the script instance
+	friend class ScriptSystem;
+	//! Flag to indicate if script->init() has been called already
+	bool initialized = false;
 	std::unique_ptr<Script> script = nullptr;
+
+private:
+	//! Script accesses the component manager directly via its parent
+	// (BehaviorScript) reference
+	friend class Script;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/BehaviorScript.hpp b/src/crepe/api/BehaviorScript.hpp
index 4751607..bb5d829 100644
--- a/src/crepe/api/BehaviorScript.hpp
+++ b/src/crepe/api/BehaviorScript.hpp
@@ -11,10 +11,10 @@ namespace crepe {
 
 template <class T>
 BehaviorScript & BehaviorScript::set_script() {
-	static_assert(std::is_base_of<Script, T>::value);
 	dbg_trace();
+	static_assert(std::is_base_of<Script, T>::value);
 	Script * s = new T();
-	s->parent = this;
+	s->parent_ref = this;
 	this->script = std::unique_ptr<Script>(s);
 	return *this;
 }
diff --git a/src/crepe/api/CMakeLists.txt b/src/crepe/api/CMakeLists.txt
index 85696c4..d9cda57 100644
--- a/src/crepe/api/CMakeLists.txt
+++ b/src/crepe/api/CMakeLists.txt
@@ -14,11 +14,11 @@ target_sources(crepe PUBLIC
 	Config.cpp
 	Metadata.cpp
 	Scene.cpp
-	SceneManager.cpp
+	# SceneManager.cpp
 	Vector2.cpp
 	Camera.cpp
 	Animator.cpp
-	LoopManager.cpp
+	# LoopManager.cpp
 	LoopTimer.cpp
 )
 
@@ -40,10 +40,10 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	SaveManager.h
 	Scene.h
 	Metadata.h
-	SceneManager.h
-	SceneManager.hpp
+	# SceneManager.h
+	# SceneManager.hpp
 	Camera.h
 	Animator.h
-	LoopManager.h
+	# LoopManager.h
 	LoopTimer.h
 )
diff --git a/src/crepe/api/Camera.cpp b/src/crepe/api/Camera.cpp
index 6355a03..fece199 100644
--- a/src/crepe/api/Camera.cpp
+++ b/src/crepe/api/Camera.cpp
@@ -1,6 +1,3 @@
-
-#include <cstdint>
-
 #include "util/log.h"
 
 #include "Camera.h"
@@ -9,8 +6,8 @@
 
 using namespace crepe;
 
-Camera::Camera(uint32_t id, const Color & bg_color)
-	: Component(id),
+Camera::Camera(const Component::Data & data, const Color & bg_color)
+	: Component(data),
 	  bg_color(bg_color) {
 	dbg_trace();
 }
diff --git a/src/crepe/api/Camera.h b/src/crepe/api/Camera.h
index ba3a9ef..a52f2f7 100644
--- a/src/crepe/api/Camera.h
+++ b/src/crepe/api/Camera.h
@@ -23,7 +23,7 @@ public:
 	 * \param id Unique identifier for the camera component.
 	 * \param bg_color Background color for the camera view.
 	 */
-	Camera(uint32_t id, const Color & bg_color);
+	Camera(const Component::Data & data, const Color & bg_color);
 	~Camera(); // dbg_trace only
 
 public:
diff --git a/src/crepe/api/GameObject.cpp b/src/crepe/api/GameObject.cpp
index d252e77..bba1f26 100644
--- a/src/crepe/api/GameObject.cpp
+++ b/src/crepe/api/GameObject.cpp
@@ -6,18 +6,19 @@
 using namespace crepe;
 using namespace std;
 
-GameObject::GameObject(game_object_id_t id, const std::string & name,
+GameObject::GameObject(ComponentManager & component_manager, game_object_id_t id, const std::string & name,
 					   const std::string & tag, const Vector2 & position,
 					   double rotation, double scale)
-	: id(id) {
+	: id(id), component_manager(component_manager) {
+
 	// Add Transform and Metadata components
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	mgr.add_component<Transform>(this->id, position, rotation, scale);
 	mgr.add_component<Metadata>(this->id, name, tag);
 }
 
 void GameObject::set_parent(const GameObject & parent) {
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 
 	// Set parent on own Metadata component
 	vector<reference_wrapper<Metadata>> this_metadata
diff --git a/src/crepe/api/GameObject.h b/src/crepe/api/GameObject.h
index d703730..d09938a 100644
--- a/src/crepe/api/GameObject.h
+++ b/src/crepe/api/GameObject.h
@@ -3,10 +3,11 @@
 #include <string>
 
 #include "types.h"
+#include "Vector2.h"
 
 namespace crepe {
 
-class Vector2;
+class ComponentManager;
 
 /**
  * \brief Represents a GameObject
@@ -16,11 +17,12 @@ class Vector2;
  * done in the ComponentManager.
  */
 class GameObject {
-public:
+private:
 	/**
 	 * This constructor creates a new GameObject. It creates a new
 	 * Transform and Metadata component and adds them to the ComponentManager.
 	 * 
+	 * \param component_manager Reference to component_manager
 	 * \param id The id of the GameObject
 	 * \param name The name of the GameObject
 	 * \param tag The tag of the GameObject
@@ -28,9 +30,11 @@ public:
 	 * \param rotation The rotation of the GameObject
 	 * \param scale The scale of the GameObject
 	 */
-	GameObject(game_object_id_t id, const std::string & name,
-			   const std::string & tag, const Vector2 & position,
-			   double rotation, double scale);
+	GameObject(ComponentManager & component_manager, game_object_id_t id, const std::string & name, const std::string & tag, const Vector2 & position, double rotation, double scale);
+	//! ComponentManager instances GameObject
+	friend class ComponentManager;
+
+public:
 	/**
 	 * \brief Set the parent of this GameObject
 	 * 
@@ -58,6 +62,9 @@ public:
 public:
 	//! The id of the GameObject
 	const game_object_id_t id;
+
+protected:
+	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/GameObject.hpp b/src/crepe/api/GameObject.hpp
index bfba7fe..17b17d7 100644
--- a/src/crepe/api/GameObject.hpp
+++ b/src/crepe/api/GameObject.hpp
@@ -8,7 +8,7 @@ namespace crepe {
 
 template <typename T, typename... Args>
 T & GameObject::add_component(Args &&... args) {
-	ComponentManager & mgr = ComponentManager::get_instance();
+	ComponentManager & mgr = this->component_manager;
 	return mgr.add_component<T>(this->id, std::forward<Args>(args)...);
 }
 
diff --git a/src/crepe/api/Metadata.cpp b/src/crepe/api/Metadata.cpp
index d421de5..6f0a280 100644
--- a/src/crepe/api/Metadata.cpp
+++ b/src/crepe/api/Metadata.cpp
@@ -3,7 +3,7 @@
 using namespace crepe;
 using namespace std;
 
-Metadata::Metadata(game_object_id_t id, const string & name, const string & tag)
-	: Component(id),
+Metadata::Metadata(const Component::Data & data, const string & name, const string & tag)
+	: Component(data),
 	  name(name),
 	  tag(tag) {}
diff --git a/src/crepe/api/Metadata.h b/src/crepe/api/Metadata.h
index c61e006..8c91797 100644
--- a/src/crepe/api/Metadata.h
+++ b/src/crepe/api/Metadata.h
@@ -20,7 +20,7 @@ public:
 	 * \param name The name of the GameObject
 	 * \param tag The tag of the GameObject
 	 */
-	Metadata(game_object_id_t id, const std::string & name,
+	Metadata(const Component::Data & data, const std::string & name,
 			 const std::string & tag);
 	/**
 	 * \brief Get the maximum number of instances for this component
diff --git a/src/crepe/api/ParticleEmitter.cpp b/src/crepe/api/ParticleEmitter.cpp
index 0bc2197..ed4fec8 100644
--- a/src/crepe/api/ParticleEmitter.cpp
+++ b/src/crepe/api/ParticleEmitter.cpp
@@ -6,12 +6,12 @@
 
 using namespace crepe;
 
-ParticleEmitter::ParticleEmitter(game_object_id_t id, uint32_t max_particles,
+ParticleEmitter::ParticleEmitter(const Component::Data & data, uint32_t max_particles,
 								 uint32_t emission_rate, uint32_t speed,
 								 uint32_t speed_offset, uint32_t angle,
 								 uint32_t angleOffset, float begin_lifespan,
 								 float end_lifespan)
-	: Component(id),
+	: Component(data),
 	  max_particles(max_particles),
 	  emission_rate(emission_rate),
 	  speed(speed),
diff --git a/src/crepe/api/ParticleEmitter.h b/src/crepe/api/ParticleEmitter.h
index 5939723..ba89538 100644
--- a/src/crepe/api/ParticleEmitter.h
+++ b/src/crepe/api/ParticleEmitter.h
@@ -10,7 +10,7 @@ namespace crepe {
 
 class ParticleEmitter : public Component {
 public:
-	ParticleEmitter(game_object_id_t id, uint32_t max_particles,
+	ParticleEmitter(const Component::Data & data, uint32_t max_particles,
 					uint32_t emission_rate, uint32_t speed,
 					uint32_t speed_offset, uint32_t angle, uint32_t angleOffset,
 					float begin_lifespan, float end_lifespan);
diff --git a/src/crepe/api/Rigidbody.cpp b/src/crepe/api/Rigidbody.cpp
index 3bf1c5b..be6bb93 100644
--- a/src/crepe/api/Rigidbody.cpp
+++ b/src/crepe/api/Rigidbody.cpp
@@ -2,8 +2,8 @@
 
 using namespace crepe;
 
-crepe::Rigidbody::Rigidbody(uint32_t game_object_id, const Data & data)
-	: Component(game_object_id),
+crepe::Rigidbody::Rigidbody(const Component::Data & component_data, const Data & data)
+	: Component(component_data),
 	  data(data) {}
 
 void crepe::Rigidbody::add_force_linear(const Vector2 & force) {
diff --git a/src/crepe/api/Rigidbody.h b/src/crepe/api/Rigidbody.h
index 68481f4..99837a6 100644
--- a/src/crepe/api/Rigidbody.h
+++ b/src/crepe/api/Rigidbody.h
@@ -82,7 +82,7 @@ public:
 	 * \param game_object_id id of the gameobject the rigibody is added to.
 	 * \param data struct to configure the rigidbody.
 	 */
-	Rigidbody(uint32_t game_object_id, const Data & data);
+	Rigidbody(const Component::Data & component_data, const Data & data);
 	//! struct to hold data of rigidbody
 	Data data;
 
diff --git a/src/crepe/api/Script.cpp b/src/crepe/api/Script.cpp
index 390cec7..0423315 100644
--- a/src/crepe/api/Script.cpp
+++ b/src/crepe/api/Script.cpp
@@ -1,3 +1,4 @@
 #include "Script.h"
 
 using namespace crepe;
+
diff --git a/src/crepe/api/Script.h b/src/crepe/api/Script.h
index 49e625f..d543df8 100644
--- a/src/crepe/api/Script.h
+++ b/src/crepe/api/Script.h
@@ -11,6 +11,7 @@ namespace crepe {
 class BehaviorScript;
 
 class Script {
+	//! ScriptSystem calls \c update()
 	friend class crepe::ScriptSystem;
 
 protected:
@@ -22,17 +23,25 @@ protected:
 	// added event.
 
 protected:
+	//! Retrieve component from component manager (utility)
 	template <typename T>
 	T & get_component();
 
+	//! Retrieve components from component manager (utility)
 	template <typename T>
 	std::vector<std::reference_wrapper<T>> get_components();
 
-private:
-	friend class crepe::BehaviorScript;
-	BehaviorScript * parent = nullptr;
+protected:
+	// NOTE: Script must have a constructor without arguments so the game
+	// programmer doesn't need to manually add `using Script::Script` to their
+	// concrete script class.
+	Script() = default;
+	//! Only \c BehaviorScript instantiates Script
+	friend class BehaviorScript;
+	BehaviorScript * parent_ref = nullptr;
 };
 
 } // namespace crepe
 
 #include "Script.hpp"
+
diff --git a/src/crepe/api/Script.hpp b/src/crepe/api/Script.hpp
index d96c0e8..68bcc29 100644
--- a/src/crepe/api/Script.hpp
+++ b/src/crepe/api/Script.hpp
@@ -18,8 +18,10 @@ T & Script::get_component() {
 
 template <typename T>
 std::vector<std::reference_wrapper<T>> Script::get_components() {
-	ComponentManager & mgr = ComponentManager::get_instance();
-	return mgr.get_components_by_id<T>(this->parent->game_object_id);
+	auto & parent = *this->parent_ref;
+	auto & mgr = parent.data.component_manager;
+
+	return mgr.get_components_by_id<T>(parent.data.id);
 }
 
 } // namespace crepe
diff --git a/src/crepe/api/Sprite.cpp b/src/crepe/api/Sprite.cpp
index 6f0433f..716609f 100644
--- a/src/crepe/api/Sprite.cpp
+++ b/src/crepe/api/Sprite.cpp
@@ -10,9 +10,9 @@
 using namespace std;
 using namespace crepe;
 
-Sprite::Sprite(game_object_id_t id, const shared_ptr<Texture> image,
+Sprite::Sprite(const Component::Data & data, const shared_ptr<Texture> image,
 			   const Color & color, const FlipSettings & flip)
-	: Component(id),
+	: Component(data),
 	  color(color),
 	  flip(flip),
 	  sprite_image(image) {
diff --git a/src/crepe/api/Sprite.h b/src/crepe/api/Sprite.h
index deb3f93..171dfeb 100644
--- a/src/crepe/api/Sprite.h
+++ b/src/crepe/api/Sprite.h
@@ -43,7 +43,7 @@ public:
 	 * \param color Color tint applied to the sprite.
 	 * \param flip Flip settings for horizontal and vertical orientation.
 	 */
-	Sprite(game_object_id_t id, const std::shared_ptr<Texture> image,
+	Sprite(const Component::Data & data, const std::shared_ptr<Texture> image,
 		   const Color & color, const FlipSettings & flip);
 
 	/**
diff --git a/src/crepe/api/Transform.cpp b/src/crepe/api/Transform.cpp
index e401120..9645d03 100644
--- a/src/crepe/api/Transform.cpp
+++ b/src/crepe/api/Transform.cpp
@@ -4,9 +4,9 @@
 
 using namespace crepe;
 
-Transform::Transform(game_object_id_t id, const Vector2 & point,
+Transform::Transform(const Component::Data & data, const Vector2 & point,
 					 double rotation, double scale)
-	: Component(id),
+	: Component(data),
 	  position(point),
 	  rotation(rotation),
 	  scale(scale) {
diff --git a/src/crepe/api/Transform.h b/src/crepe/api/Transform.h
index 756e45b..a7bcd89 100644
--- a/src/crepe/api/Transform.h
+++ b/src/crepe/api/Transform.h
@@ -20,7 +20,7 @@ public:
 	 * \param rotation The rotation of the GameObject
 	 * \param scale The scale of the GameObject
 	 */
-	Transform(game_object_id_t id, const Vector2 & point, double rotation,
+	Transform(const Component::Data & data, const Vector2 & point, double rotation,
 			  double scale);
 	/**
 	 * \brief Get the maximum number of instances for this component
diff --git a/src/crepe/facade/Sound.cpp b/src/crepe/facade/Sound.cpp
index 648ec81..3a6e1e1 100644
--- a/src/crepe/facade/Sound.cpp
+++ b/src/crepe/facade/Sound.cpp
@@ -1,26 +1,24 @@
+#include <memory>
+
 #include "../util/log.h"
+#include "../Asset.h"
 
 #include "Sound.h"
 #include "SoundContext.h"
 
 using namespace crepe;
+using namespace std;
 
-Sound::Sound(std::unique_ptr<Asset> res) {
-	dbg_trace();
-	this->load(std::move(res));
-}
+Sound::Sound(SoundContext & ctx) : context(ctx) { dbg_trace(); }
 
-Sound::Sound(const char * src) {
-	dbg_trace();
-	this->load(std::make_unique<Asset>(src));
-}
-
-void Sound::load(std::unique_ptr<Asset> res) {
-	this->sample.load(res->canonical());
+unique_ptr<Resource> Sound::clone(const Asset & src) const {
+	auto instance = make_unique<Sound>(*this);
+	instance->sample.load(src.canonical());
+	return instance;
 }
 
 void Sound::play() {
-	SoundContext & ctx = SoundContext::get_instance();
+	SoundContext & ctx = this->context;
 	if (ctx.engine.getPause(this->handle)) {
 		// resume if paused
 		ctx.engine.setPause(this->handle, false);
@@ -32,13 +30,13 @@ void Sound::play() {
 }
 
 void Sound::pause() {
-	SoundContext & ctx = SoundContext::get_instance();
+	SoundContext & ctx = this->context;
 	if (ctx.engine.getPause(this->handle)) return;
 	ctx.engine.setPause(this->handle, true);
 }
 
 void Sound::rewind() {
-	SoundContext & ctx = SoundContext::get_instance();
+	SoundContext & ctx = this->context;
 	if (!ctx.engine.isValidVoiceHandle(this->handle)) return;
 	ctx.engine.seek(this->handle, 0);
 }
@@ -46,7 +44,7 @@ void Sound::rewind() {
 void Sound::set_volume(float volume) {
 	this->volume = volume;
 
-	SoundContext & ctx = SoundContext::get_instance();
+	SoundContext & ctx = this->context;
 	if (!ctx.engine.isValidVoiceHandle(this->handle)) return;
 	ctx.engine.setVolume(this->handle, this->volume);
 }
@@ -54,7 +52,8 @@ void Sound::set_volume(float volume) {
 void Sound::set_looping(bool looping) {
 	this->looping = looping;
 
-	SoundContext & ctx = SoundContext::get_instance();
+	SoundContext & ctx = this->context;
 	if (!ctx.engine.isValidVoiceHandle(this->handle)) return;
 	ctx.engine.setLooping(this->handle, this->looping);
 }
+
diff --git a/src/crepe/facade/Sound.h b/src/crepe/facade/Sound.h
index 183bd7c..e5b2f19 100644
--- a/src/crepe/facade/Sound.h
+++ b/src/crepe/facade/Sound.h
@@ -4,11 +4,13 @@
 #include <soloud/soloud.h>
 #include <soloud/soloud_wav.h>
 
-#include "../Asset.h"
+#include "../Resource.h"
 
 namespace crepe {
 
-class Sound {
+class SoundContext;
+
+class Sound : public Resource {
 public:
 	/**
 	 * \brief Pause this sample
@@ -64,15 +66,13 @@ public:
 	bool get_looping() const { return this->looping; }
 
 public:
-	Sound(const char * src);
-	Sound(std::unique_ptr<Asset> res);
-
-private:
-	void load(std::unique_ptr<Asset> res);
+	Sound(SoundContext & ctx);
+	std::unique_ptr<Resource> clone(const Asset & src) const override;
 
 private:
 	SoLoud::Wav sample;
 	SoLoud::handle handle;
+	SoundContext & context;
 
 	float volume = 1.0f;
 	bool looping = false;
diff --git a/src/crepe/facade/SoundContext.cpp b/src/crepe/facade/SoundContext.cpp
index 5e5a3a9..c89fb03 100644
--- a/src/crepe/facade/SoundContext.cpp
+++ b/src/crepe/facade/SoundContext.cpp
@@ -4,11 +4,6 @@
 
 using namespace crepe;
 
-SoundContext & SoundContext::get_instance() {
-	static SoundContext instance;
-	return instance;
-}
-
 SoundContext::SoundContext() {
 	dbg_trace();
 	engine.init();
@@ -18,3 +13,4 @@ SoundContext::~SoundContext() {
 	dbg_trace();
 	engine.deinit();
 }
+
diff --git a/src/crepe/facade/SoundContext.h b/src/crepe/facade/SoundContext.h
index d3123d2..c360fb8 100644
--- a/src/crepe/facade/SoundContext.h
+++ b/src/crepe/facade/SoundContext.h
@@ -7,19 +7,18 @@
 namespace crepe {
 
 class SoundContext {
-private:
+public:
 	SoundContext();
 	virtual ~SoundContext();
 
-	// singleton
-	static SoundContext & get_instance();
-	SoundContext(const SoundContext &) = delete;
-	SoundContext(SoundContext &&) = delete;
-	SoundContext & operator=(const SoundContext &) = delete;
-	SoundContext & operator=(SoundContext &&) = delete;
+  SoundContext(const SoundContext &) = delete;
+  SoundContext(SoundContext &&) = delete;
+  SoundContext & operator=(const SoundContext &) = delete;
+  SoundContext & operator=(SoundContext &&) = delete;
 
 private:
 	SoLoud::Soloud engine;
+	//! Sound directly calls methods on \c engine
 	friend class Sound;
 };
 
diff --git a/src/crepe/system/CMakeLists.txt b/src/crepe/system/CMakeLists.txt
index 4c18b87..9ee12f6 100644
--- a/src/crepe/system/CMakeLists.txt
+++ b/src/crepe/system/CMakeLists.txt
@@ -1,17 +1,18 @@
 target_sources(crepe PUBLIC
-	ParticleSystem.cpp
+	System.cpp
+	# ParticleSystem.cpp
 	ScriptSystem.cpp
-	PhysicsSystem.cpp
-	CollisionSystem.cpp
-	RenderSystem.cpp
-	AnimatorSystem.cpp
+	# PhysicsSystem.cpp
+	# CollisionSystem.cpp
+	# RenderSystem.cpp
+	# AnimatorSystem.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	System.h
 	ScriptSystem.h
-	PhysicsSystem.h
-	CollisionSystem.h
-	RenderSystem.h
-	AnimatorSystem.h
+	# PhysicsSystem.h
+	# CollisionSystem.h
+	# RenderSystem.h
+	# AnimatorSystem.h
 )
diff --git a/src/crepe/system/ScriptSystem.cpp b/src/crepe/system/ScriptSystem.cpp
index f2673e7..0a87fcc 100644
--- a/src/crepe/system/ScriptSystem.cpp
+++ b/src/crepe/system/ScriptSystem.cpp
@@ -13,16 +13,24 @@ using namespace std;
 using namespace crepe;
 
 void ScriptSystem::update() {
-	using namespace std;
 	dbg_trace();
 
-	forward_list<Script *> scripts = this->get_scripts();
-	for (Script * script : scripts) script->update();
+	forward_list<reference_wrapper<Script>> scripts = this->get_scripts();
+
+	for (auto & script_ref : scripts) {
+		Script & script = script_ref.get();
+		BehaviorScript & component = *script.parent_ref;
+		if (!component.initialized) {
+			script.init();
+			component.initialized = true;
+		}
+		script.update();
+	}
 }
 
-forward_list<Script *> ScriptSystem::get_scripts() {
-	forward_list<Script *> scripts = {};
-	ComponentManager & mgr = ComponentManager::get_instance();
+forward_list<reference_wrapper<Script>> ScriptSystem::get_scripts() {
+	forward_list<reference_wrapper<Script>> scripts = {};
+	ComponentManager & mgr = this->component_manager;
 	vector<reference_wrapper<BehaviorScript>> behavior_scripts
 		= mgr.get_components_by_type<BehaviorScript>();
 
@@ -31,8 +39,9 @@ forward_list<Script *> ScriptSystem::get_scripts() {
 		if (!behavior_script.active) continue;
 		Script * script = behavior_script.script.get();
 		if (script == nullptr) continue;
-		scripts.push_front(script);
+		scripts.push_front(*script);
 	}
 
 	return scripts;
 }
+
diff --git a/src/crepe/system/ScriptSystem.h b/src/crepe/system/ScriptSystem.h
index 4fa6141..b52e825 100644
--- a/src/crepe/system/ScriptSystem.h
+++ b/src/crepe/system/ScriptSystem.h
@@ -7,14 +7,15 @@
 namespace crepe {
 
 class Script;
+class BehaviorScript;
 
 class ScriptSystem : public System {
 public:
+	using System::System;
 	void update();
 
 private:
-	// TODO: to forward_list<reference_wrapper>
-	std::forward_list<Script *> get_scripts();
+	std::forward_list<std::reference_wrapper<Script>> get_scripts();
 };
 
 } // namespace crepe
diff --git a/src/crepe/system/System.cpp b/src/crepe/system/System.cpp
new file mode 100644
index 0000000..296f1ed
--- /dev/null
+++ b/src/crepe/system/System.cpp
@@ -0,0 +1,6 @@
+#include "System.h"
+
+using namespace crepe;
+
+System::System(ComponentManager & mgr) : component_manager(mgr) {}
+
diff --git a/src/crepe/system/System.h b/src/crepe/system/System.h
index 3b81bef..7970e72 100644
--- a/src/crepe/system/System.h
+++ b/src/crepe/system/System.h
@@ -2,13 +2,18 @@
 
 namespace crepe {
 
+class ComponentManager;
+
 class System {
 public:
 	virtual void update() = 0;
 
 public:
-	System() = default;
+	System(ComponentManager &);
 	virtual ~System() = default;
+
+protected:
+	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index 0e4eaed..9d303bc 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -1,6 +1,6 @@
 target_sources(test_main PUBLIC
-	dummy.cpp
-	# audio.cpp
-	PhysicsTest.cpp
+	main.cpp
+	# PhysicsTest.cpp
+	ScriptTest.cpp
 )
 
diff --git a/src/test/PhysicsTest.cpp b/src/test/PhysicsTest.cpp
index 5385962..538d244 100644
--- a/src/test/PhysicsTest.cpp
+++ b/src/test/PhysicsTest.cpp
@@ -11,9 +11,11 @@ using namespace std::chrono_literals;
 using namespace crepe;
 
 class PhysicsTest : public ::testing::Test {
-protected:
+public:
 	GameObject * game_object;
+	ComponentManager component_manager;
 	PhysicsSystem physics_system;
+
 	void SetUp() override {
 		ComponentManager & mgr = ComponentManager::get_instance();
 		std::vector<std::reference_wrapper<Transform>> transforms
diff --git a/src/test/ScriptTest.cpp b/src/test/ScriptTest.cpp
new file mode 100644
index 0000000..ea49a35
--- /dev/null
+++ b/src/test/ScriptTest.cpp
@@ -0,0 +1,73 @@
+#include <gtest/gtest.h>
+
+// stupid hack to allow access to private/protected members under test
+#define private public
+#define protected public
+
+#include <crepe/ComponentManager.h>
+#include <crepe/system/ScriptSystem.h>
+#include <crepe/api/BehaviorScript.h>
+#include <crepe/api/Script.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/Vector2.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class ScriptTest : public Test {
+public:
+	ComponentManager component_manager {};
+	ScriptSystem system { component_manager };
+
+	class MyScript : public Script {
+		// NOTE: default (private) visibility of init and update shouldn't cause
+		// issues!
+		void init() { this->init_count++; }
+		void update() { this->update_count++; }
+
+	public:
+		unsigned init_count = 0;
+		unsigned update_count = 0;
+	};
+
+	BehaviorScript * behaviorscript_ref = nullptr;
+	MyScript * script_ref = nullptr;
+
+	void SetUp() override {
+		auto & mgr = this->component_manager;
+		GameObject & entity = mgr.new_object("name");
+		BehaviorScript & component = entity.add_component<BehaviorScript>();
+
+		this->behaviorscript_ref = &component;
+		EXPECT_EQ(this->behaviorscript_ref->script.get(), nullptr);
+		component.set_script<MyScript>();
+		ASSERT_NE(this->behaviorscript_ref->script.get(), nullptr);
+
+		this->script_ref = (MyScript *) this->behaviorscript_ref->script.get();
+		ASSERT_NE(this->script_ref, nullptr);
+	}
+};
+
+TEST_F(ScriptTest, Default) {
+	EXPECT_EQ(0, this->script_ref->init_count);
+	EXPECT_EQ(0, this->script_ref->update_count);
+}
+
+TEST_F(ScriptTest, UpdateOnce) {
+	EXPECT_EQ(0, this->script_ref->init_count);
+	EXPECT_EQ(0, this->script_ref->update_count);
+
+	this->system.update();
+	EXPECT_EQ(1, this->script_ref->init_count);
+	EXPECT_EQ(1, this->script_ref->update_count);
+}
+
+TEST_F(ScriptTest, ListScripts) {
+	size_t script_count = 0;
+	for (auto & _ : this->system.get_scripts()) {
+		script_count++;
+	}
+	ASSERT_EQ(1, script_count);
+}
+
diff --git a/src/test/audio.cpp b/src/test/audio.cpp
deleted file mode 100644
index d6ff689..0000000
--- a/src/test/audio.cpp
+++ /dev/null
@@ -1,10 +0,0 @@
-#include <gtest/gtest.h>
-
-using namespace std;
-using namespace std::chrono_literals;
-
-// using namespace crepe;
-
-// TODO: mock internal audio class
-
-TEST(audio, play) { ASSERT_TRUE(true); }
diff --git a/src/test/dummy.cpp b/src/test/dummy.cpp
deleted file mode 100644
index a00a9c6..0000000
--- a/src/test/dummy.cpp
+++ /dev/null
@@ -1,3 +0,0 @@
-#include <gtest/gtest.h>
-
-TEST(dummy, foo) { ASSERT_TRUE(1); }
diff --git a/src/test/main.cpp b/src/test/main.cpp
new file mode 100644
index 0000000..6830a01
--- /dev/null
+++ b/src/test/main.cpp
@@ -0,0 +1,15 @@
+#include <crepe/api/Config.h>
+
+#include <gtest/gtest.h>
+
+using namespace crepe;
+using namespace testing;
+
+int main(int argc, char **argv) {
+  InitGoogleTest(&argc, argv);
+
+	auto & cfg = Config::get_instance();
+	cfg.log.level = LogLevel::ERROR;
+
+  return RUN_ALL_TESTS();
+}