merge master

57 files changed, 540 insertions, 263 deletions

diff --git a/Doxyfile b/Doxyfile
index f2714cd..07c86d1 100644
--- a/Doxyfile
+++ b/Doxyfile
@@ -17,11 +17,10 @@ GENERATE_LATEX = NO
 LAYOUT_FILE = src/doc/layout.xml
 TAB_SIZE = 2
 
-HTML_INDEX_NUM_ENTRIES = 2
+HTML_INDEX_NUM_ENTRIES = 999
 HTML_EXTRA_STYLESHEET = src/doc/style.css
 SHOW_HEADERFILE = NO
 
-USE_MDFILE_AS_MAINPAGE = ./readme.md
 REPEAT_BRIEF = NO
 
 EXTRACT_STATIC = YES
@@ -29,6 +28,7 @@ HIDE_UNDOC_NAMESPACES = YES
 HIDE_UNDOC_CLASSES = YES
 
 QUIET = YES
+WARNINGS = NO
 
 # set these to NO for user-only docs
 INTERNAL_DOCS = YES
diff --git a/contributing.md b/contributing.md
index b0f623b..7dedaa7 100644
--- a/contributing.md
+++ b/contributing.md
@@ -635,15 +635,21 @@ that you can click on to open them.
   </summary><table><tr><th>Good</th><th>Bad</th></tr><tr><td>
 
   ```cpp
+  void Foo::bar() { }
+
   void Foo::set_value(int value) {
     this->value = value;
+    this->bar();
   }
   ```
   </td><td>
 
   ```cpp
+  void Foo::bar() { }
+
   void Foo::set_value(int new_value) {
     value = new_value;
+    bar();
   }
   ```
   </td></tr></table></details>
@@ -868,6 +874,8 @@ that you can click on to open them.
 
 # Documentation
 
+[Doxygen commands](https://www.doxygen.nl/manual/commands.html)
+
 - All documentation is written in U.S. English
 - <details><summary>
   Doxygen commands are used with a backslash instead of an at-sign.
@@ -953,6 +961,52 @@ that you can click on to open them.
   Foo & operator=(Foo &&) = delete;
   ```
   </td></tr></table></details>
+- Do not use markdown headings in Doxygen
+
+## Documenting features
+
+Engine features are small 'building blocks' that the user (game developer) may
+reference when building a game with the engine. Features do not necessarily map
+1-1 to engine components or systems. If a component or system has a single,
+distinct feature it should be named after that feature, not the component or
+system itself.
+
+The sources for these pages are located under `src/doc/feature/`, and have the
+following format:
+
+- A feature description which explains—
+  - the purpose and function of the feature (focus on what it enables or
+    achieves for the user)
+  - additional information about when to implement the feature, such as specific
+    use cases or scenarios
+- A list of 'see also' references to relevant classes and/or types
+- A **minimal** example to demonstrate how the feature is used. The example
+  should be written such that the following is clear to the reader:
+  - Which headers need to be included to utilize the feature
+  - *Why* the example works, not what is happening in the example
+  - Where is this code supposed to be called (e.g. inside scene/script
+    functions)
+  - Which restrictions should be kept in mind (e.g. copy/move semantics, max
+    component instances, speed considerations)
+
+Features should be documented as clear and concise as possible, so the following
+points should be kept in mind:
+
+- <details><summary>
+  If a page expands on an example from another page, directly reference the
+  other page using a cross-reference (`\ref`) in a `\note` block at the top of
+  the page.
+  </summary>
+
+  ```
+  \note This page builds on top of the example shown in \ref feature_script
+  ```
+  </details>
+- When explaining the usage of specific functions, qualify them such that
+  Doxygen is able to add a cross-reference or manually add a reference using the
+  `\ref` command.
+- Users will likely copy-paste examples as-is, so do this yourself to check if
+  the example code actually works!
 
 # Libraries
 
@@ -960,4 +1014,6 @@ that you can click on to open them.
   subdirectory
 - When adding new submodules, please set the `shallow` option to `true` in the
   [.gitmodules](./.gitmodules) file
+- When adding new libraries, please update the library version table in
+  [readme\.md](./readme.md)
 
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index c3f29da..97b21f0 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -40,5 +40,6 @@ install(
 
 target_link_libraries(test_main
 	PRIVATE gtest
+	PRIVATE gmock
 	PUBLIC crepe
 )
diff --git a/src/crepe/CMakeLists.txt b/src/crepe/CMakeLists.txt
index 7e176e7..da9d492 100644
--- a/src/crepe/CMakeLists.txt
+++ b/src/crepe/CMakeLists.txt
@@ -1,13 +1,10 @@
 target_sources(crepe PUBLIC
 	Particle.cpp
-	ComponentManager.cpp
 	Component.cpp
 	Collider.cpp
 )
 
 target_sources(crepe PUBLIC FILE_SET HEADERS FILES
-	ComponentManager.h
-	ComponentManager.hpp
 	Component.h
 	Collider.h
 	ValueBroker.h
@@ -16,6 +13,7 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 
 add_subdirectory(api)
 add_subdirectory(facade)
+add_subdirectory(manager)
 add_subdirectory(system)
 add_subdirectory(util)
 
diff --git a/src/crepe/api/BehaviorScript.cpp b/src/crepe/api/BehaviorScript.cpp
index 7bbace0..d22afdf 100644
--- a/src/crepe/api/BehaviorScript.cpp
+++ b/src/crepe/api/BehaviorScript.cpp
@@ -4,12 +4,12 @@
 
 using namespace crepe;
 
-BehaviorScript::BehaviorScript(game_object_id_t id, ComponentManager & mgr)
+BehaviorScript::BehaviorScript(game_object_id_t id, Mediator & mediator)
 	: Component(id),
-	  component_manager(mgr) {}
+	  mediator(mediator) {}
 
 template <>
 BehaviorScript & GameObject::add_component<BehaviorScript>() {
 	ComponentManager & mgr = this->component_manager;
-	return mgr.add_component<BehaviorScript>(this->id, mgr);
+	return mgr.add_component<BehaviorScript>(this->id, mgr.mediator);
 }
diff --git a/src/crepe/api/BehaviorScript.h b/src/crepe/api/BehaviorScript.h
index d556fe5..3909b96 100644
--- a/src/crepe/api/BehaviorScript.h
+++ b/src/crepe/api/BehaviorScript.h
@@ -23,14 +23,13 @@ class BehaviorScript : public Component {
 protected:
 	/**
 	 * \param id Parent \c GameObject id
-	 * \param component_manager Reference to component manager (passed through to \c Script
-	 * instance)
+	 * \param mediator Mediator reference
 	 *
 	 * \note Calls to this constructor (should) always pass through \c GameObject::add_component,
 	 * which has an exception for this specific component type. This was done so the user does
 	 * not have to pass references used within \c Script to each \c BehaviorScript instance.
 	 */
-	BehaviorScript(game_object_id_t id, ComponentManager & component_manager);
+	BehaviorScript(game_object_id_t id, Mediator & mediator);
 	//! Only ComponentManager is allowed to instantiate BehaviorScript
 	friend class ComponentManager;
 
@@ -55,8 +54,8 @@ protected:
 	friend class ScriptSystem;
 
 protected:
-	//! Reference to component manager (passed to Script)
-	ComponentManager & component_manager;
+	//! Reference mediator
+	Mediator & mediator;
 };
 
 /**
diff --git a/src/crepe/api/BehaviorScript.hpp b/src/crepe/api/BehaviorScript.hpp
index bd59337..b9bb1e2 100644
--- a/src/crepe/api/BehaviorScript.hpp
+++ b/src/crepe/api/BehaviorScript.hpp
@@ -13,14 +13,12 @@ template <class T, typename... Args>
 BehaviorScript & BehaviorScript::set_script(Args &&... args) {
 	dbg_trace();
 	static_assert(std::is_base_of<Script, T>::value);
-	Script * s = new T(std::forward<Args>(args)...);
+	this->script = std::unique_ptr<Script>(new T(std::forward<Args>(args)...));
 
-	s->game_object_id = this->game_object_id;
-	s->active = this->active;
-	s->component_manager = this->component_manager;
-	s->event_manager = EventManager::get_instance();
+	this->script->game_object_id = this->game_object_id;
+	this->script->active = this->active;
+	this->script->mediator = this->mediator;
 
-	this->script = std::unique_ptr<Script>(s);
 	return *this;
 }
 
diff --git a/src/crepe/api/CMakeLists.txt b/src/crepe/api/CMakeLists.txt
index 25a9439..ac8f301 100644
--- a/src/crepe/api/CMakeLists.txt
+++ b/src/crepe/api/CMakeLists.txt
@@ -9,13 +9,10 @@ target_sources(crepe PUBLIC
 	Texture.cpp
 	AssetManager.cpp
 	Sprite.cpp
-	SaveManager.cpp
 	Config.cpp
 	Metadata.cpp
-	SceneManager.cpp
 	Camera.cpp
 	Animator.cpp
-	EventManager.cpp
 	IKeyListener.cpp
 	IMouseListener.cpp
 	LoopManager.cpp
@@ -43,15 +40,10 @@ target_sources(crepe PUBLIC FILE_SET HEADERS FILES
 	Texture.h 
 	AssetManager.h 
 	AssetManager.hpp
-	SaveManager.h
 	Scene.h
 	Metadata.h
-	SceneManager.h
-	SceneManager.hpp
 	Camera.h
 	Animator.h
-	EventManager.h
-	EventManager.hpp
 	EventHandler.h
 	EventHandler.hpp
 	Event.h
diff --git a/src/crepe/api/GameObject.hpp b/src/crepe/api/GameObject.hpp
index 17b17d7..a6b45b0 100644
--- a/src/crepe/api/GameObject.hpp
+++ b/src/crepe/api/GameObject.hpp
@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../ComponentManager.h"
+#include "../manager/ComponentManager.h"
 
 #include "GameObject.h"
 
diff --git a/src/crepe/api/IKeyListener.h b/src/crepe/api/IKeyListener.h
index 328a4c2..6ded107 100644
--- a/src/crepe/api/IKeyListener.h
+++ b/src/crepe/api/IKeyListener.h
@@ -1,8 +1,9 @@
 #pragma once
 
+#include "../manager/EventManager.h"
+
 #include "Event.h"
 #include "EventHandler.h"
-#include "EventManager.h"
 
 namespace crepe {
 
diff --git a/src/crepe/api/IMouseListener.h b/src/crepe/api/IMouseListener.h
index 15e1619..9e4fdf7 100644
--- a/src/crepe/api/IMouseListener.h
+++ b/src/crepe/api/IMouseListener.h
@@ -1,8 +1,9 @@
 #pragma once
 
+#include "../manager/EventManager.h"
+
 #include "Event.h"
 #include "EventHandler.h"
-#include "EventManager.h"
 
 namespace crepe {
 
diff --git a/src/crepe/api/LoopManager.cpp b/src/crepe/api/LoopManager.cpp
index b343250..dc2d9e0 100644
--- a/src/crepe/api/LoopManager.cpp
+++ b/src/crepe/api/LoopManager.cpp
@@ -1,5 +1,3 @@
-#include "../facade/SDLContext.h"
-
 #include "../system/AnimatorSystem.h"
 #include "../system/CollisionSystem.h"
 #include "../system/InputSystem.h"
@@ -9,12 +7,14 @@
 #include "../system/ScriptSystem.h"
 
 #include "LoopManager.h"
-#include "LoopTimer.h"
 
 using namespace crepe;
 using namespace std;
 
 LoopManager::LoopManager() {
+	this->mediator.component_manager = this->component_manager;
+	this->mediator.scene_manager = this->scene_manager;
+
 	this->load_system<AnimatorSystem>();
 	this->load_system<CollisionSystem>();
 	this->load_system<ParticleSystem>();
@@ -35,7 +35,7 @@ void LoopManager::set_running(bool running) { this->game_running = running; }
 void LoopManager::fixed_update() {}
 
 void LoopManager::loop() {
-	LoopTimer & timer = LoopTimer::get_instance();
+	LoopTimer & timer = this->loop_timer;
 	timer.start();
 
 	while (game_running) {
@@ -55,15 +55,17 @@ void LoopManager::loop() {
 }
 
 void LoopManager::setup() {
+	LoopTimer & timer = this->loop_timer;
+
 	this->game_running = true;
-	LoopTimer::get_instance().start();
-	LoopTimer::get_instance().set_fps(200);
+	timer.start();
+	timer.set_fps(200);
 }
 
 void LoopManager::render() {
-	if (this->game_running) {
-		this->get_system<RenderSystem>().update();
-	}
+	if (!this->game_running) return;
+
+	this->get_system<RenderSystem>().update();
 }
 
-void LoopManager::update() { LoopTimer & timer = LoopTimer::get_instance(); }
+void LoopManager::update() {}
diff --git a/src/crepe/api/LoopManager.h b/src/crepe/api/LoopManager.h
index 13e6dac..d8910a0 100644
--- a/src/crepe/api/LoopManager.h
+++ b/src/crepe/api/LoopManager.h
@@ -2,9 +2,12 @@
 
 #include <memory>
 
-#include "../ComponentManager.h"
+#include "../facade/SDLContext.h"
+#include "../manager/ComponentManager.h"
+#include "../manager/SceneManager.h"
 #include "../system/System.h"
-#include "api/SceneManager.h"
+
+#include "LoopTimer.h"
 
 namespace crepe {
 
@@ -85,10 +88,18 @@ private:
 	bool game_running = false;
 
 private:
+	//! Global context
+	Mediator mediator;
+
 	//! Component manager instance
-	ComponentManager component_manager{};
+	ComponentManager component_manager{mediator};
 	//! Scene manager instance
-	SceneManager scene_manager{component_manager};
+	SceneManager scene_manager{mediator};
+
+	//! SDL context \todo no more singletons!
+	SDLContext & sdl_context = SDLContext::get_instance();
+	//! Loop timer \todo no more singletons!
+	LoopTimer & loop_timer = LoopTimer::get_instance();
 
 private:
 	/**
diff --git a/src/crepe/api/LoopManager.hpp b/src/crepe/api/LoopManager.hpp
index 9cf470b..266758a 100644
--- a/src/crepe/api/LoopManager.hpp
+++ b/src/crepe/api/LoopManager.hpp
@@ -38,8 +38,11 @@ void LoopManager::load_system() {
 	static_assert(is_base_of<System, T>::value,
 				  "load_system must recieve a derivative class of System");
 
-	System * system = new T(this->component_manager);
-	this->systems[typeid(T)] = unique_ptr<System>(system);
+	const type_info & type = typeid(T);
+	if (this->systems.contains(type))
+		throw runtime_error(format("LoopManager: {} is already initialized", type.name()));
+	System * system = new T(this->mediator);
+	this->systems[type] = unique_ptr<System>(system);
 }
 
 } // namespace crepe
diff --git a/src/crepe/api/Scene.h b/src/crepe/api/Scene.h
index f6fdb2a..9f1e8ce 100644
--- a/src/crepe/api/Scene.h
+++ b/src/crepe/api/Scene.h
@@ -2,6 +2,7 @@
 
 #include <string>
 
+#include "../manager/Mediator.h"
 #include "../util/OptionalRef.h"
 
 namespace crepe {
@@ -34,6 +35,9 @@ public:
 	 */
 	virtual std::string get_name() const = 0;
 
+	// TODO: Late references should ALWAYS be private! This is currently kept as-is so unit tests
+	// keep passing, but this reference should not be directly accessible by the user!!!
+
 protected:
 	/**
 	 * \name Late references
@@ -46,8 +50,8 @@ protected:
 	 *
 	 * \{
 	 */
-	//! Reference to the ComponentManager
-	OptionalRef<ComponentManager> component_manager;
+	//! Mediator reference
+	OptionalRef<Mediator> mediator;
 	//! \}
 };
 
diff --git a/src/crepe/api/Script.cpp b/src/crepe/api/Script.cpp
index fcbe4c7..4091fd4 100644
--- a/src/crepe/api/Script.cpp
+++ b/src/crepe/api/Script.cpp
@@ -1,11 +1,17 @@
+#include <string>
+
+#include "../manager/SceneManager.h"
+
 #include "Script.h"
 
 using namespace crepe;
+using namespace std;
 
 Script::~Script() {
-	EventManager & evmgr = this->event_manager;
+	Mediator & mediator = this->mediator;
+	EventManager & mgr = mediator.event_manager;
 	for (auto id : this->listeners) {
-		evmgr.unsubscribe(id);
+		mgr.unsubscribe(id);
 	}
 }
 
@@ -13,3 +19,9 @@ template <>
 void Script::subscribe(const EventHandler<CollisionEvent> & callback) {
 	this->subscribe_internal(callback, this->game_object_id);
 }
+
+void Script::set_next_scene(const string & name) {
+	Mediator & mediator = this->mediator;
+	SceneManager & mgr = mediator.scene_manager;
+	mgr.set_next_scene(name);
+}
diff --git a/src/crepe/api/Script.h b/src/crepe/api/Script.h
index a0870cb..1b339b0 100644
--- a/src/crepe/api/Script.h
+++ b/src/crepe/api/Script.h
@@ -2,11 +2,11 @@
 
 #include <vector>
 
+#include "../manager/EventManager.h"
+#include "../manager/Mediator.h"
 #include "../types.h"
 #include "../util/OptionalRef.h"
 
-#include "EventManager.h"
-
 namespace crepe {
 
 class ScriptSystem;
@@ -106,6 +106,12 @@ protected:
 	template <typename EventType>
 	void subscribe(const EventHandler<EventType> & callback);
 
+	/**
+	 * \brief Set the next scene using SceneManager
+	 * \see SceneManager::set_next_scene
+	 */
+	void set_next_scene(const std::string & name);
+
 	//! \}
 
 private:
@@ -160,10 +166,8 @@ private:
 	game_object_id_t game_object_id;
 	//! Reference to parent component
 	OptionalRef<bool> active;
-	//! Reference to component manager instance
-	OptionalRef<ComponentManager> component_manager;
-	//! Reference to event manager instance
-	OptionalRef<EventManager> event_manager;
+	//! Mediator reference
+	OptionalRef<Mediator> mediator;
 	//! \}
 
 private:
diff --git a/src/crepe/api/Script.hpp b/src/crepe/api/Script.hpp
index a2463bf..45f1ff1 100644
--- a/src/crepe/api/Script.hpp
+++ b/src/crepe/api/Script.hpp
@@ -1,6 +1,6 @@
 #pragma once
 
-#include "../ComponentManager.h"
+#include "../manager/ComponentManager.h"
 
 #include "BehaviorScript.h"
 #include "Script.h"
@@ -20,7 +20,8 @@ T & Script::get_component() const {
 
 template <typename T>
 RefVector<T> Script::get_components() const {
-	ComponentManager & mgr = this->component_manager;
+	Mediator & mediator = this->mediator;
+	ComponentManager & mgr = mediator.component_manager;
 
 	return mgr.get_components_by_id<T>(this->game_object_id);
 }
@@ -33,7 +34,8 @@ void Script::logf(Args &&... args) {
 template <typename EventType>
 void Script::subscribe_internal(const EventHandler<EventType> & callback,
 								event_channel_t channel) {
-	EventManager & mgr = this->event_manager;
+	Mediator & mediator = this->mediator;
+	EventManager & mgr = mediator.event_manager;
 	subscription_t listener = mgr.subscribe<EventType>(
 		[this, callback](const EventType & data) -> bool {
 			bool & active = this->active;
diff --git a/src/crepe/manager/CMakeLists.txt b/src/crepe/manager/CMakeLists.txt
new file mode 100644
index 0000000..517b8a2
--- /dev/null
+++ b/src/crepe/manager/CMakeLists.txt
@@ -0,0 +1,20 @@
+target_sources(crepe PUBLIC
+	ComponentManager.cpp
+	EventManager.cpp
+	Manager.cpp
+	SaveManager.cpp
+	SceneManager.cpp
+)
+
+target_sources(crepe PUBLIC FILE_SET HEADERS FILES
+	ComponentManager.h
+	ComponentManager.hpp
+	EventManager.h
+	EventManager.hpp
+	Manager.h
+	Mediator.h
+	SaveManager.h
+	SceneManager.h
+	SceneManager.hpp
+)
+
diff --git a/src/crepe/ComponentManager.cpp b/src/crepe/manager/ComponentManager.cpp
index 5b73009..80cf8b4 100644
--- a/src/crepe/ComponentManager.cpp
+++ b/src/crepe/manager/ComponentManager.cpp
@@ -1,13 +1,16 @@
-#include "api/GameObject.h"
-#include "util/Log.h"
+#include "../api/GameObject.h"
+#include "../types.h"
+#include "../util/Log.h"
 
 #include "ComponentManager.h"
-#include "types.h"
 
 using namespace crepe;
 using namespace std;
 
-ComponentManager::ComponentManager() { dbg_trace(); }
+ComponentManager::ComponentManager(Mediator & mediator) : Manager(mediator) {
+	mediator.component_manager = *this;
+	dbg_trace();
+}
 ComponentManager::~ComponentManager() { dbg_trace(); }
 
 void ComponentManager::delete_all_components_of_id(game_object_id_t id) {
diff --git a/src/crepe/ComponentManager.h b/src/crepe/manager/ComponentManager.h
index 480124f..ad37586 100644
--- a/src/crepe/ComponentManager.h
+++ b/src/crepe/manager/ComponentManager.h
@@ -5,8 +5,10 @@
 #include <unordered_map>
 #include <vector>
 
-#include "Component.h"
-#include "types.h"
+#include "../Component.h"
+#include "../types.h"
+
+#include "Manager.h"
 
 namespace crepe {
 
@@ -17,7 +19,7 @@ class GameObject;
  * 
  * This class manages all components. It provides methods to add, delete and get components.
  */
-class ComponentManager {
+class ComponentManager : public Manager {
 	// TODO: This relation should be removed! I (loek) believe that the scene manager should
 	// create/destroy components because the GameObject's are stored in concrete Scene classes,
 	// which will in turn call GameObject's destructor, which will in turn call
@@ -26,7 +28,7 @@ class ComponentManager {
 	friend class SceneManager;
 
 public:
-	ComponentManager(); // dbg_trace
+	ComponentManager(Mediator & mediator);
 	~ComponentManager(); // dbg_trace
 
 	/**
diff --git a/src/crepe/ComponentManager.hpp b/src/crepe/manager/ComponentManager.hpp
index ffb38ec..ffb38ec 100644
--- a/src/crepe/ComponentManager.hpp
+++ b/src/crepe/manager/ComponentManager.hpp
diff --git a/src/crepe/api/EventManager.cpp b/src/crepe/manager/EventManager.cpp
index 20f0dd3..20f0dd3 100644
--- a/src/crepe/api/EventManager.cpp
+++ b/src/crepe/manager/EventManager.cpp
diff --git a/src/crepe/api/EventManager.h b/src/crepe/manager/EventManager.h
index 1a33023..d634f54 100644
--- a/src/crepe/api/EventManager.h
+++ b/src/crepe/manager/EventManager.h
@@ -5,8 +5,8 @@
 #include <unordered_map>
 #include <vector>
 
-#include "Event.h"
-#include "EventHandler.h"
+#include "../api/Event.h"
+#include "../api/EventHandler.h"
 
 namespace crepe {
 
diff --git a/src/crepe/api/EventManager.hpp b/src/crepe/manager/EventManager.hpp
index a5f4556..a5f4556 100644
--- a/src/crepe/api/EventManager.hpp
+++ b/src/crepe/manager/EventManager.hpp
diff --git a/src/crepe/manager/Manager.cpp b/src/crepe/manager/Manager.cpp
new file mode 100644
index 0000000..1182785
--- /dev/null
+++ b/src/crepe/manager/Manager.cpp
@@ -0,0 +1,5 @@
+#include "Manager.h"
+
+using namespace crepe;
+
+Manager::Manager(Mediator & mediator) : mediator(mediator) {}
diff --git a/src/crepe/manager/Manager.h b/src/crepe/manager/Manager.h
new file mode 100644
index 0000000..84d80fe
--- /dev/null
+++ b/src/crepe/manager/Manager.h
@@ -0,0 +1,24 @@
+#pragma once
+
+#include "Mediator.h"
+
+namespace crepe {
+
+/**
+ * \brief Base manager class
+ *
+ * Managers are used for various tasks that fall outside the ECS system category. All managers
+ * are required to register themselves to the mediator passed to the constructor, and this
+ * mutable reference is saved for convenience, even though not all managers use the mediator
+ * directly.
+ */
+class Manager {
+public:
+	Manager(Mediator & mediator);
+	virtual ~Manager() = default;
+
+protected:
+	Mediator & mediator;
+};
+
+} // namespace crepe
diff --git a/src/crepe/manager/Mediator.h b/src/crepe/manager/Mediator.h
new file mode 100644
index 0000000..71bd1c9
--- /dev/null
+++ b/src/crepe/manager/Mediator.h
@@ -0,0 +1,33 @@
+#pragma once
+
+#include "../util/OptionalRef.h"
+
+// TODO: remove these singletons:
+#include "EventManager.h"
+#include "SaveManager.h"
+
+namespace crepe {
+
+class ComponentManager;
+class SceneManager;
+
+/**
+ * Struct to pass references to classes that would otherwise need to be singletons down to
+ * other classes within the engine hierarchy. Made to prevent constant changes to subclasses to
+ * pass specific references through dependency injection. All references on this struct
+ * *should* be explicitly checked for availability as this struct does not guarantee anything.
+ *
+ * \note Dereferencing members of this struct should be deferred. If you are a user of this
+ * class, keep a reference to this mediator instead of just picking references from it when you
+ * receive an instance.
+ *
+ * \warning This class should never be directly accessible from the API
+ */
+struct Mediator {
+	OptionalRef<ComponentManager> component_manager;
+	OptionalRef<SceneManager> scene_manager;
+	OptionalRef<SaveManager> save_manager = SaveManager::get_instance();
+	OptionalRef<EventManager> event_manager = EventManager::get_instance();
+};
+
+} // namespace crepe
diff --git a/src/crepe/api/SaveManager.cpp b/src/crepe/manager/SaveManager.cpp
index c5f43ea..d4ed1c1 100644
--- a/src/crepe/api/SaveManager.cpp
+++ b/src/crepe/manager/SaveManager.cpp
@@ -1,9 +1,9 @@
+#include "../ValueBroker.h"
+#include "../api/Config.h"
 #include "../facade/DB.h"
 #include "../util/Log.h"
 
-#include "Config.h"
 #include "SaveManager.h"
-#include "ValueBroker.h"
 
 using namespace std;
 using namespace crepe;
diff --git a/src/crepe/api/SaveManager.h b/src/crepe/manager/SaveManager.h
index 3d8c852..3d8c852 100644
--- a/src/crepe/api/SaveManager.h
+++ b/src/crepe/manager/SaveManager.h
diff --git a/src/crepe/api/SceneManager.cpp b/src/crepe/manager/SceneManager.cpp
index 1f783ad..50a9fbb 100644
--- a/src/crepe/api/SceneManager.cpp
+++ b/src/crepe/manager/SceneManager.cpp
@@ -1,14 +1,15 @@
 #include <algorithm>
 #include <memory>
 
-#include "../ComponentManager.h"
-
+#include "ComponentManager.h"
 #include "SceneManager.h"
 
 using namespace crepe;
 using namespace std;
 
-SceneManager::SceneManager(ComponentManager & mgr) : component_manager(mgr) {}
+SceneManager::SceneManager(Mediator & mediator) : Manager(mediator) {
+	mediator.scene_manager = *this;
+}
 
 void SceneManager::set_next_scene(const string & name) { next_scene = name; }
 
@@ -26,7 +27,7 @@ void SceneManager::load_next_scene() {
 	unique_ptr<Scene> & scene = *it;
 
 	// Delete all components of the current scene
-	ComponentManager & mgr = this->component_manager;
+	ComponentManager & mgr = this->mediator.component_manager;
 	mgr.delete_all_components();
 
 	// Load the new scene
diff --git a/src/crepe/api/SceneManager.h b/src/crepe/manager/SceneManager.h
index f6f62cd..e0955c2 100644
--- a/src/crepe/api/SceneManager.h
+++ b/src/crepe/manager/SceneManager.h
@@ -3,7 +3,9 @@
 #include <memory>
 #include <vector>
 
-#include "Scene.h"
+#include "../api/Scene.h"
+
+#include "Manager.h"
 
 namespace crepe {
 
@@ -15,10 +17,9 @@ class ComponentManager;
  * This class manages scenes. It can add new scenes and load them. It also manages the current scene
  * and the next scene.
  */
-class SceneManager {
+class SceneManager : public Manager {
 public:
-	//! \param mgr  Reference to the ComponentManager
-	SceneManager(ComponentManager & mgr);
+	SceneManager(Mediator & mediator);
 
 public:
 	/**
@@ -44,8 +45,6 @@ private:
 	std::vector<std::unique_ptr<Scene>> scenes;
 	//! Next scene to load
 	std::string next_scene;
-	//! Reference to the ComponentManager
-	ComponentManager & component_manager;
 };
 
 } // namespace crepe
diff --git a/src/crepe/api/SceneManager.hpp b/src/crepe/manager/SceneManager.hpp
index 5c8e417..dff4e51 100644
--- a/src/crepe/api/SceneManager.hpp
+++ b/src/crepe/manager/SceneManager.hpp
@@ -12,7 +12,7 @@ void SceneManager::add_scene(Args &&... args) {
 	Scene * scene = new T(std::forward<Args>(args)...);
 	unique_ptr<Scene> unique_scene(scene);
 
-	unique_scene->component_manager = this->component_manager;
+	unique_scene->mediator = this->mediator;
 
 	this->scenes.emplace_back(std::move(unique_scene));
 
diff --git a/src/crepe/system/AnimatorSystem.cpp b/src/crepe/system/AnimatorSystem.cpp
index 4c40940..8bb6465 100644
--- a/src/crepe/system/AnimatorSystem.cpp
+++ b/src/crepe/system/AnimatorSystem.cpp
@@ -1,15 +1,15 @@
 #include <cstdint>
 
-#include "api/Animator.h"
-#include "facade/SDLContext.h"
+#include "../api/Animator.h"
+#include "../facade/SDLContext.h"
+#include "../manager/ComponentManager.h"
 
 #include "AnimatorSystem.h"
-#include "ComponentManager.h"
 
 using namespace crepe;
 
 void AnimatorSystem::update() {
-	ComponentManager & mgr = this->component_manager;
+	ComponentManager & mgr = this->mediator.component_manager;
 
 	RefVector<Animator> animations = mgr.get_components_by_type<Animator>();
 
diff --git a/src/crepe/system/ParticleSystem.cpp b/src/crepe/system/ParticleSystem.cpp
index 0e62a57..b14c52f 100644
--- a/src/crepe/system/ParticleSystem.cpp
+++ b/src/crepe/system/ParticleSystem.cpp
@@ -2,17 +2,17 @@
 #include <cstdlib>
 #include <ctime>
 
-#include "api/ParticleEmitter.h"
-#include "api/Transform.h"
+#include "../api/ParticleEmitter.h"
+#include "../api/Transform.h"
+#include "../manager/ComponentManager.h"
 
-#include "ComponentManager.h"
 #include "ParticleSystem.h"
 
 using namespace crepe;
 
 void ParticleSystem::update() {
 	// Get all emitters
-	ComponentManager & mgr = this->component_manager;
+	ComponentManager & mgr = this->mediator.component_manager;
 	RefVector<ParticleEmitter> emitters = mgr.get_components_by_type<ParticleEmitter>();
 
 	for (ParticleEmitter & emitter : emitters) {
diff --git a/src/crepe/system/PhysicsSystem.cpp b/src/crepe/system/PhysicsSystem.cpp
index 514a4b3..bebcf3d 100644
--- a/src/crepe/system/PhysicsSystem.cpp
+++ b/src/crepe/system/PhysicsSystem.cpp
@@ -1,17 +1,17 @@
 #include <cmath>
 
-#include "../ComponentManager.h"
 #include "../api/Config.h"
 #include "../api/Rigidbody.h"
 #include "../api/Transform.h"
 #include "../api/Vector2.h"
+#include "../manager/ComponentManager.h"
 
 #include "PhysicsSystem.h"
 
 using namespace crepe;
 
 void PhysicsSystem::update() {
-	ComponentManager & mgr = this->component_manager;
+	ComponentManager & mgr = this->mediator.component_manager;
 	RefVector<Rigidbody> rigidbodies = mgr.get_components_by_type<Rigidbody>();
 	RefVector<Transform> transforms = mgr.get_components_by_type<Transform>();
 
diff --git a/src/crepe/system/RenderSystem.cpp b/src/crepe/system/RenderSystem.cpp
index 11c9669..92dba43 100644
--- a/src/crepe/system/RenderSystem.cpp
+++ b/src/crepe/system/RenderSystem.cpp
@@ -5,12 +5,12 @@
 #include <stdexcept>
 #include <vector>
 
-#include "../ComponentManager.h"
 #include "../api/Camera.h"
 #include "../api/ParticleEmitter.h"
 #include "../api/Sprite.h"
 #include "../api/Transform.h"
 #include "../facade/SDLContext.h"
+#include "../manager/ComponentManager.h"
 
 #include "RenderSystem.h"
 
@@ -22,7 +22,7 @@ void RenderSystem::clear_screen() { this->context.clear_screen(); }
 void RenderSystem::present_screen() { this->context.present_screen(); }
 
 const Camera & RenderSystem::update_camera() {
-	ComponentManager & mgr = this->component_manager;
+	ComponentManager & mgr = this->mediator.component_manager;
 
 	RefVector<Camera> cameras = mgr.get_components_by_type<Camera>();
 
@@ -62,7 +62,7 @@ void RenderSystem::update() {
 bool RenderSystem::render_particle(const Sprite & sprite, const Camera & cam,
 								   const double & scale) {
 
-	ComponentManager & mgr = this->component_manager;
+	ComponentManager & mgr = this->mediator.component_manager;
 
 	vector<reference_wrapper<ParticleEmitter>> emitters
 		= mgr.get_components_by_id<ParticleEmitter>(sprite.game_object_id);
@@ -102,7 +102,7 @@ void RenderSystem::render_normal(const Sprite & sprite, const Camera & cam,
 }
 
 void RenderSystem::render() {
-	ComponentManager & mgr = this->component_manager;
+	ComponentManager & mgr = this->mediator.component_manager;
 	const Camera & cam = this->update_camera();
 
 	RefVector<Sprite> sprites = mgr.get_components_by_type<Sprite>();
diff --git a/src/crepe/system/ScriptSystem.cpp b/src/crepe/system/ScriptSystem.cpp
index 20a83f7..d6b2ca1 100644
--- a/src/crepe/system/ScriptSystem.cpp
+++ b/src/crepe/system/ScriptSystem.cpp
@@ -1,6 +1,6 @@
-#include "../ComponentManager.h"
 #include "../api/BehaviorScript.h"
 #include "../api/Script.h"
+#include "../manager/ComponentManager.h"
 
 #include "ScriptSystem.h"
 
@@ -10,7 +10,7 @@ using namespace crepe;
 void ScriptSystem::update() {
 	dbg_trace();
 
-	ComponentManager & mgr = this->component_manager;
+	ComponentManager & mgr = this->mediator.component_manager;
 	RefVector<BehaviorScript> behavior_scripts = mgr.get_components_by_type<BehaviorScript>();
 
 	for (BehaviorScript & behavior_script : behavior_scripts) {
diff --git a/src/crepe/system/System.cpp b/src/crepe/system/System.cpp
index 937a423..f68549b 100644
--- a/src/crepe/system/System.cpp
+++ b/src/crepe/system/System.cpp
@@ -4,4 +4,4 @@
 
 using namespace crepe;
 
-System::System(ComponentManager & mgr) : component_manager(mgr) { dbg_trace(); }
+System::System(const Mediator & mediator) : mediator(mediator) { dbg_trace(); }
diff --git a/src/crepe/system/System.h b/src/crepe/system/System.h
index 28ea20e..063dfbf 100644
--- a/src/crepe/system/System.h
+++ b/src/crepe/system/System.h
@@ -1,5 +1,7 @@
 #pragma once
 
+#include "../manager/Mediator.h"
+
 namespace crepe {
 
 class ComponentManager;
@@ -7,9 +9,8 @@ class ComponentManager;
 /**
  * \brief Base ECS system class
  *
- * This class is used as the base for all system classes. Classes derived from
- * System must implement the System::update() method and copy Script::Script
- * with the `using`-syntax.
+ * This class is used as the base for all system classes. Classes derived from System must
+ * implement the System::update() method and copy Script::Script with the `using`-syntax.
  */
 class System {
 public:
@@ -19,11 +20,11 @@ public:
 	virtual void update() = 0;
 
 public:
-	System(ComponentManager &);
+	System(const Mediator & m);
 	virtual ~System() = default;
 
 protected:
-	ComponentManager & component_manager;
+	const Mediator & mediator;
 };
 
 } // namespace crepe
diff --git a/src/doc/feature/scene.dox b/src/doc/feature/scene.dox
index d81df4c..4124e37 100644
--- a/src/doc/feature/scene.dox
+++ b/src/doc/feature/scene.dox
@@ -6,10 +6,11 @@ namespace crepe {
 \ingroup feature
 \brief User-defined scenes
 
-Scenes can be used to implement game environments, and allow arbitrary game objects to be organized
-as part of the game structure. Scenes are implemented as derivative classes of Scene, which are
-added to the game using the SceneManager. Scenes describe the start of a Scene and cannot modify
-GameObjects during runtime of a Scene (use \ref feature_script "Scripting" for this purpose).
+Scenes can be used to implement game environments, and allow arbitrary game
+objects to be organized as part of the game structure. Scenes are implemented as
+derivative classes of Scene, which are added to the game using the SceneManager.
+Scenes describe the start of a Scene and cannot modify GameObjects during
+runtime of a Scene (use \ref feature_script for this purpose).
 
 \see SceneManager
 \see GameObject
@@ -18,19 +19,25 @@ GameObjects during runtime of a Scene (use \ref feature_script "Scripting" for t
 
 \par Example
 
-This example demonstrates how to define and add scenes to the loop/scene manager in the `crepe` framework.
-Each concrete scene should be derived from Scene. In the example below, the concrete scene is named MyScene.
-A concrete scene should, at least, implement (override) two methods, namely load_scene() and get_name(). The
-scene is build (using GameObjects) in the load_scene() method. GameObjects should be made using the
-component_manager::new_object(). In the example below, two GameObjects (named object1 and object2) are added
-to MyScene. object1 and object2 do not have any non-default Components attached to them, however, if needed,
-this should also be done in load_scene(). Each concrete scene must have a unique name. This unique name is
-used to load a new concrete scene (via a Script). The unique name is set using the get_name() method. In the
-example below, MyScene's unique name is my_scene.
-After setting up one or more concrete scene(s), the concrete scene(s) should be added to the loop/scene manager.
-This is done in your main(). Firstly, the LoopManager should be instantiated. Than, all the concrete scene(s)
-should be added to the loop/scene manger via loop_mgr::add_scene<>(). The templated argument should define the
-concrete scene to be added.
+This example demonstrates how to define and add scenes to the loop/scene manager
+in the `crepe` framework. Each concrete scene should be derived from Scene. In
+the example below, the concrete scene is named MyScene. A concrete scene should,
+at least, implement (override) two methods, namely load_scene() and get_name().
+The scene is build (using GameObjects) in the load_scene() method. GameObjects
+should be made using the component_manager::new_object().
+
+In the example below, two GameObjects (named object1 and object2) are added to
+MyScene. object1 and object2 do not have any non-default Components attached to
+them, however, if needed, this should also be done in load_scene(). Each
+concrete scene must have a unique name. This unique name is used to load a new
+concrete scene (via a Script). The unique name is set using the get_name()
+method. In the example below, MyScene's unique name is my_scene.
+
+After setting up one or more concrete scene(s), the concrete scene(s) should be
+added to the loop/scene manager. This is done in your main(). Firstly, the
+LoopManager should be instantiated. Than, all the concrete scene(s) should be
+added to the loop/scene manger via loop_mgr::add_scene<>(). The templated
+argument should define the concrete scene to be added.
 
 ```cpp
 #include <crepe/api/LoopManager.h>
diff --git a/src/doc/features.dox b/src/doc/features.dox
index 4786bed..21a040a 100644
--- a/src/doc/features.dox
+++ b/src/doc/features.dox
@@ -1,10 +1,28 @@
 // vim:ft=doxygen
 /**
 
+\htmlonly
+<style>
+table.memberdecls { display: none; }
+ul { margin: 1ex 0pt; }
+</style>
+\endhtmlonly
+
 \defgroup feature Features
 \brief Engine components
 
 This page lists engine features and contains usage instructions for each
 feature.
 
+\par Features
+
+- Scripting
+	- \ref feature_script \n\copybrief feature_script
+
+- Game flow management
+	- \ref feature_scene \n\copybrief feature_scene
+
+- Entity
+	- \ref feature_gameobject \n\copybrief feature_gameobject
+
 */
diff --git a/src/doc/index.dox b/src/doc/index.dox
index 5ec7889..7796f34 100644
--- a/src/doc/index.dox
+++ b/src/doc/index.dox
@@ -8,3 +8,10 @@ Welcome to the documentation for the crêpe game engine.
 \see feature
 
 */
+
+/**
+
+\namespace crepe
+\brief Engine namespace
+
+*/
diff --git a/src/doc/layout.xml b/src/doc/layout.xml
index fb4cc0c..6336655 100644
--- a/src/doc/layout.xml
+++ b/src/doc/layout.xml
@@ -11,7 +11,7 @@
 			<tab type="modulelist" visible="yes" title="" intro=""/>
 			<tab type="modulemembers" visible="yes" title="" intro=""/>
 		</tab>
-		<tab type="namespaces" visible="no" title="">
+		<tab type="namespaces" visible="yes" title="">
 			<tab type="namespacelist" visible="yes" title="" intro=""/>
 			<tab type="namespacemembers" visible="yes" title="" intro=""/>
 		</tab>
@@ -56,10 +56,10 @@
 			<interfaces title=""/>
 			<publicslots title=""/>
 			<signals title=""/>
-			<publicmethods title=""/>
-			<publicstaticmethods title=""/>
 			<publicattributes title=""/>
 			<publicstaticattributes title=""/>
+			<publicmethods title=""/>
+			<publicstaticmethods title=""/>
 			<protectedtypes title=""/>
 			<protectedslots title=""/>
 			<protectedmethods title=""/>
@@ -102,11 +102,12 @@
 	</class>
 	<namespace>
 		<briefdescription visible="yes"/>
+		<detaileddescription title=""/>
 		<memberdecl>
 			<nestednamespaces visible="yes" title=""/>
 			<constantgroups visible="yes" title=""/>
 			<interfaces visible="yes" title=""/>
-			<classes visible="yes" title=""/>
+			<classes visible="no" title=""/>
 			<concepts visible="yes" title=""/>
 			<structs visible="yes" title=""/>
 			<exceptions visible="yes" title=""/>
@@ -119,7 +120,6 @@
 			<properties title=""/>
 			<membergroups visible="yes"/>
 		</memberdecl>
-		<detaileddescription title=""/>
 		<memberdef>
 			<inlineclasses title=""/>
 			<typedefs title=""/>
diff --git a/src/doc/style.css b/src/doc/style.css
index daabd39..c12240c 100644
--- a/src/doc/style.css
+++ b/src/doc/style.css
@@ -1,6 +1,6 @@
 #titlearea,
-address {
-	display: none;
-}
+address,
+a[href="namespaces.html"]
+{ display: none; }
 
 h2.groupheader { margin-top: revert; }
diff --git a/src/test/CMakeLists.txt b/src/test/CMakeLists.txt
index dd4a754..e19d7de 100644
--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -13,4 +13,6 @@ target_sources(test_main PUBLIC
 	DBTest.cpp
 	Vector2Test.cpp
 	InputTest.cpp
+	ScriptEventTest.cpp
+	ScriptSceneTest.cpp
 )
diff --git a/src/test/DBTest.cpp b/src/test/DBTest.cpp
index e80814c..99dedff 100644
--- a/src/test/DBTest.cpp
+++ b/src/test/DBTest.cpp
@@ -1,6 +1,7 @@
-#include <crepe/facade/DB.h>
 #include <gtest/gtest.h>
 
+#include <crepe/facade/DB.h>
+
 using namespace std;
 using namespace crepe;
 using namespace testing;
diff --git a/src/test/ECSTest.cpp b/src/test/ECSTest.cpp
index af9d6f2..3e6c61c 100644
--- a/src/test/ECSTest.cpp
+++ b/src/test/ECSTest.cpp
@@ -2,18 +2,20 @@
 
 #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>
+#include <crepe/manager/ComponentManager.h>
 
 using namespace std;
 using namespace crepe;
 
 class ECSTest : public ::testing::Test {
+	Mediator m;
+
 public:
-	ComponentManager mgr{};
+	ComponentManager mgr{m};
 };
 
 TEST_F(ECSTest, createGameObject) {
diff --git a/src/test/EventTest.cpp b/src/test/EventTest.cpp
index c75bcc1..4a4872d 100644
--- a/src/test/EventTest.cpp
+++ b/src/test/EventTest.cpp
@@ -1,10 +1,11 @@
-
-#include "api/Event.h"
-#include "api/EventManager.h"
-#include "api/IKeyListener.h"
-#include "api/IMouseListener.h"
 #include <gmock/gmock.h>
 #include <gtest/gtest.h>
+
+#include <crepe/api/Event.h>
+#include <crepe/api/IKeyListener.h>
+#include <crepe/api/IMouseListener.h>
+#include <crepe/manager/EventManager.h>
+
 using namespace std;
 using namespace std::chrono_literals;
 using namespace crepe;
@@ -36,10 +37,7 @@ public:
 };
 
 TEST_F(EventManagerTest, EventSubscription) {
-	EventHandler<KeyPressEvent> key_handler = [](const KeyPressEvent & e) {
-		std::cout << "Key Event Triggered" << std::endl;
-		return true;
-	};
+	EventHandler<KeyPressEvent> key_handler = [](const KeyPressEvent & e) { return true; };
 
 	// Subscribe to KeyPressEvent
 	EventManager::get_instance().subscribe<KeyPressEvent>(key_handler, 1);
diff --git a/src/test/ParticleTest.cpp b/src/test/ParticleTest.cpp
index 976f9a1..a659fe5 100644
--- a/src/test/ParticleTest.cpp
+++ b/src/test/ParticleTest.cpp
@@ -1,12 +1,12 @@
-#include "api/Texture.h"
-#include <crepe/ComponentManager.h>
 #include <crepe/Particle.h>
 #include <crepe/api/Config.h>
 #include <crepe/api/GameObject.h>
 #include <crepe/api/ParticleEmitter.h>
 #include <crepe/api/Rigidbody.h>
 #include <crepe/api/Sprite.h>
+#include <crepe/api/Texture.h>
 #include <crepe/api/Transform.h>
+#include <crepe/manager/ComponentManager.h>
 #include <crepe/system/ParticleSystem.h>
 #include <gtest/gtest.h>
 #include <math.h>
@@ -16,9 +16,11 @@ using namespace std::chrono_literals;
 using namespace crepe;
 
 class ParticlesTest : public ::testing::Test {
+	Mediator m;
+
 public:
-	ComponentManager component_manager;
-	ParticleSystem particle_system{component_manager};
+	ComponentManager component_manager{m};
+	ParticleSystem particle_system{m};
 
 	void SetUp() override {
 		ComponentManager & mgr = this->component_manager;
diff --git a/src/test/PhysicsTest.cpp b/src/test/PhysicsTest.cpp
index 33b6020..43af8e4 100644
--- a/src/test/PhysicsTest.cpp
+++ b/src/test/PhysicsTest.cpp
@@ -1,8 +1,8 @@
-#include <crepe/ComponentManager.h>
 #include <crepe/api/Config.h>
 #include <crepe/api/GameObject.h>
 #include <crepe/api/Rigidbody.h>
 #include <crepe/api/Transform.h>
+#include <crepe/manager/ComponentManager.h>
 #include <crepe/system/PhysicsSystem.h>
 #include <gtest/gtest.h>
 
@@ -11,9 +11,11 @@ using namespace std::chrono_literals;
 using namespace crepe;
 
 class PhysicsTest : public ::testing::Test {
+	Mediator m;
+
 public:
-	ComponentManager component_manager;
-	PhysicsSystem system{component_manager};
+	ComponentManager component_manager{m};
+	PhysicsSystem system{m};
 
 	void SetUp() override {
 		ComponentManager & mgr = this->component_manager;
diff --git a/src/test/RenderSystemTest.cpp b/src/test/RenderSystemTest.cpp
index bb5b81a..c105dcb 100644
--- a/src/test/RenderSystemTest.cpp
+++ b/src/test/RenderSystemTest.cpp
@@ -1,4 +1,3 @@
-#include "types.h"
 #include <functional>
 #include <gtest/gtest.h>
 #include <memory>
@@ -7,12 +6,12 @@
 #define private public
 #define protected public
 
-#include "crepe/api/Camera.h"
-#include <crepe/ComponentManager.h>
+#include <crepe/api/Camera.h>
 #include <crepe/api/Color.h>
 #include <crepe/api/GameObject.h>
 #include <crepe/api/Sprite.h>
 #include <crepe/api/Texture.h>
+#include <crepe/manager/ComponentManager.h>
 
 #include <crepe/system/RenderSystem.h>
 
@@ -21,9 +20,11 @@ using namespace crepe;
 using namespace testing;
 
 class RenderSystemTest : public Test {
+	Mediator m;
+
 public:
-	ComponentManager mgr{};
-	RenderSystem sys{mgr};
+	ComponentManager mgr{m};
+	RenderSystem sys{m};
 	GameObject entity1 = this->mgr.new_object("name");
 	GameObject entity2 = this->mgr.new_object("name");
 	GameObject entity3 = this->mgr.new_object("name");
diff --git a/src/test/SceneManagerTest.cpp b/src/test/SceneManagerTest.cpp
index 62b7d33..9bb260c 100644
--- a/src/test/SceneManagerTest.cpp
+++ b/src/test/SceneManagerTest.cpp
@@ -1,12 +1,13 @@
-#include "types.h"
-#include <crepe/ComponentManager.h>
+#include <gtest/gtest.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>
+#include <crepe/manager/ComponentManager.h>
+#include <crepe/manager/SceneManager.h>
+#include <crepe/types.h>
 
 using namespace std;
 using namespace crepe;
@@ -14,7 +15,8 @@ using namespace crepe;
 class ConcreteScene1 : public Scene {
 public:
 	void load_scene() {
-		ComponentManager & mgr = this->component_manager;
+		Mediator & mediator = this->mediator;
+		ComponentManager & mgr = mediator.component_manager;
 		GameObject object1 = mgr.new_object("scene_1", "tag_scene_1", vec2{0, 0}, 0, 1);
 		GameObject object2 = mgr.new_object("scene_1", "tag_scene_1", vec2{1, 0}, 0, 1);
 		GameObject object3 = mgr.new_object("scene_1", "tag_scene_1", vec2{2, 0}, 0, 1);
@@ -26,7 +28,8 @@ public:
 class ConcreteScene2 : public Scene {
 public:
 	void load_scene() {
-		ComponentManager & mgr = this->component_manager;
+		Mediator & mediator = this->mediator;
+		ComponentManager & mgr = mediator.component_manager;
 		GameObject object1 = mgr.new_object("scene_2", "tag_scene_2", vec2{0, 0}, 0, 1);
 		GameObject object2 = mgr.new_object("scene_2", "tag_scene_2", vec2{0, 1}, 0, 1);
 		GameObject object3 = mgr.new_object("scene_2", "tag_scene_2", vec2{0, 2}, 0, 1);
@@ -41,7 +44,8 @@ public:
 	ConcreteScene3(const string & name) : name(name) {}
 
 	void load_scene() {
-		ComponentManager & mgr = this->component_manager;
+		Mediator & mediator = this->mediator;
+		ComponentManager & mgr = mediator.component_manager;
 		GameObject object1 = mgr.new_object("scene_3", "tag_scene_3", vec2{0, 0}, 0, 1);
 	}
 
@@ -52,9 +56,11 @@ private:
 };
 
 class SceneManagerTest : public ::testing::Test {
+	Mediator m;
+
 public:
-	ComponentManager component_mgr{};
-	SceneManager scene_mgr{component_mgr};
+	ComponentManager component_mgr{m};
+	SceneManager scene_mgr{m};
 };
 
 TEST_F(SceneManagerTest, loadScene) {
diff --git a/src/test/ScriptEventTest.cpp b/src/test/ScriptEventTest.cpp
new file mode 100644
index 0000000..5da31e7
--- /dev/null
+++ b/src/test/ScriptEventTest.cpp
@@ -0,0 +1,50 @@
+#include <gtest/gtest.h>
+
+// stupid hack to allow access to private/protected members under test
+#define private public
+#define protected public
+
+#include <crepe/api/BehaviorScript.h>
+#include <crepe/api/Event.h>
+#include <crepe/api/GameObject.h>
+#include <crepe/api/Script.h>
+#include <crepe/api/Vector2.h>
+#include <crepe/manager/ComponentManager.h>
+#include <crepe/manager/EventManager.h>
+#include <crepe/system/ScriptSystem.h>
+
+#include "ScriptTest.h"
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class ScriptEventTest : public ScriptTest {
+public:
+	EventManager & event_manager = mediator.event_manager;
+
+	class MyEvent : public Event {};
+};
+
+TEST_F(ScriptEventTest, Inactive) {
+	BehaviorScript & behaviorscript = this->behaviorscript;
+	MyScript & script = this->script;
+	EventManager & evmgr = this->event_manager;
+
+	unsigned event_count = 0;
+	script.subscribe<MyEvent>([&](const MyEvent &) {
+		event_count++;
+		return true;
+	});
+
+	system.update();
+	behaviorscript.active = false;
+	EXPECT_EQ(0, event_count);
+
+	evmgr.trigger_event<MyEvent>();
+	EXPECT_EQ(0, event_count);
+
+	behaviorscript.active = true;
+	evmgr.trigger_event<MyEvent>();
+	EXPECT_EQ(1, event_count);
+}
diff --git a/src/test/ScriptSceneTest.cpp b/src/test/ScriptSceneTest.cpp
new file mode 100644
index 0000000..9ee1e52
--- /dev/null
+++ b/src/test/ScriptSceneTest.cpp
@@ -0,0 +1,30 @@
+#include <gtest/gtest.h>
+
+// stupid hack to allow access to private/protected members under test
+#define private public
+#define protected public
+
+#include "ScriptTest.h"
+#include <crepe/manager/SceneManager.h>
+
+using namespace std;
+using namespace crepe;
+using namespace testing;
+
+class ScriptSceneTest : public ScriptTest {
+public:
+	SceneManager scene_manager{mediator};
+
+	class MyScene : public Scene {};
+};
+
+TEST_F(ScriptSceneTest, Inactive) {
+	BehaviorScript & behaviorscript = this->behaviorscript;
+	MyScript & script = this->script;
+
+	const char * non_default_value = "foo";
+	ASSERT_NE(non_default_value, scene_manager.next_scene);
+
+	script.set_next_scene(non_default_value);
+	EXPECT_EQ(non_default_value, scene_manager.next_scene);
+}
diff --git a/src/test/ScriptTest.cpp b/src/test/ScriptTest.cpp
index 78d5061..1d2d6dd 100644
--- a/src/test/ScriptTest.cpp
+++ b/src/test/ScriptTest.cpp
@@ -1,129 +1,77 @@
+#include <gmock/gmock.h>
 #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/api/BehaviorScript.h>
-#include <crepe/api/Event.h>
-#include <crepe/api/EventManager.h>
+#include "ScriptTest.h"
 #include <crepe/api/GameObject.h>
-#include <crepe/api/Script.h>
-#include <crepe/api/Vector2.h>
-#include <crepe/system/ScriptSystem.h>
 
 using namespace std;
 using namespace crepe;
 using namespace testing;
 
-class MyEvent : public Event {};
-
-class ScriptTest : public Test {
-public:
-	ComponentManager component_manager{};
-	ScriptSystem system{component_manager};
-	EventManager & event_manager = EventManager::get_instance();
-
-	class MyScript : public Script {
-		// NOTE: default (private) visibility of init and update shouldn't cause
-		// issues!
-		void init() {
-			this->init_count++;
-
-			subscribe<MyEvent>([this](const MyEvent &) {
-				this->event_count++;
-				return true;
-			});
-
-			// init should never be called more than once
-			EXPECT_LE(this->init_count, 1);
-		}
-		void update() { this->update_count++; }
-
-	public:
-		unsigned init_count = 0;
-		unsigned update_count = 0;
-		unsigned event_count = 0;
-	};
-
-	OptionalRef<BehaviorScript> behaviorscript;
-	OptionalRef<MyScript> script;
-
-	void SetUp() override {
-		auto & mgr = this->component_manager;
-		GameObject entity = mgr.new_object("name");
-		BehaviorScript & component = entity.add_component<BehaviorScript>();
-
-		this->behaviorscript = component;
-		ASSERT_TRUE(this->behaviorscript);
-		EXPECT_EQ(component.script.get(), nullptr);
-		component.set_script<MyScript>();
-		ASSERT_NE(component.script.get(), nullptr);
-
-		this->script = *(MyScript *) component.script.get();
-		ASSERT_TRUE(this->script);
-
-		// sanity
-		MyScript & script = this->script;
-		ASSERT_EQ(script.init_count, 0);
-		ASSERT_EQ(script.update_count, 0);
-		ASSERT_EQ(script.event_count, 0);
-	}
-};
+void ScriptTest::SetUp() {
+	auto & mgr = this->component_manager;
+	GameObject entity = mgr.new_object("name");
+	BehaviorScript & component = entity.add_component<BehaviorScript>();
+
+	this->behaviorscript = component;
+	ASSERT_TRUE(this->behaviorscript);
+	EXPECT_EQ(component.script.get(), nullptr);
+	component.set_script<NiceMock<MyScript>>();
+	ASSERT_NE(component.script.get(), nullptr);
+
+	this->script = *(MyScript *) component.script.get();
+	ASSERT_TRUE(this->script);
+}
 
 TEST_F(ScriptTest, Default) {
 	MyScript & script = this->script;
-	EXPECT_EQ(0, script.init_count);
-	EXPECT_EQ(0, script.update_count);
-	EXPECT_EQ(0, script.event_count);
+	EXPECT_CALL(script, init()).Times(0);
+	EXPECT_CALL(script, update()).Times(0);
 }
 
 TEST_F(ScriptTest, UpdateOnce) {
 	MyScript & script = this->script;
 
-	system.update();
-	EXPECT_EQ(1, script.init_count);
-	EXPECT_EQ(1, script.update_count);
-	EXPECT_EQ(0, script.event_count);
+	{
+		InSequence seq;
+
+		EXPECT_CALL(script, init()).Times(1);
+		EXPECT_CALL(script, update()).Times(1);
+		system.update();
+	}
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(script, init()).Times(0);
+		EXPECT_CALL(script, update()).Times(1);
+		system.update();
+	}
 }
 
 TEST_F(ScriptTest, UpdateInactive) {
 	BehaviorScript & behaviorscript = this->behaviorscript;
 	MyScript & script = this->script;
 
-	behaviorscript.active = false;
-	system.update();
-	EXPECT_EQ(0, script.init_count);
-	EXPECT_EQ(0, script.update_count);
-	EXPECT_EQ(0, script.event_count);
-
-	behaviorscript.active = true;
-	system.update();
-	EXPECT_EQ(1, script.init_count);
-	EXPECT_EQ(1, script.update_count);
-	EXPECT_EQ(0, script.event_count);
-}
+	{
+		InSequence seq;
 
-TEST_F(ScriptTest, EventInactive) {
-	BehaviorScript & behaviorscript = this->behaviorscript;
-	MyScript & script = this->script;
-	EventManager & evmgr = this->event_manager;
-
-	system.update();
-	behaviorscript.active = false;
-	EXPECT_EQ(1, script.init_count);
-	EXPECT_EQ(1, script.update_count);
-	EXPECT_EQ(0, script.event_count);
-
-	evmgr.trigger_event<MyEvent>();
-	EXPECT_EQ(1, script.init_count);
-	EXPECT_EQ(1, script.update_count);
-	EXPECT_EQ(0, script.event_count);
-
-	behaviorscript.active = true;
-	evmgr.trigger_event<MyEvent>();
-	EXPECT_EQ(1, script.init_count);
-	EXPECT_EQ(1, script.update_count);
-	EXPECT_EQ(1, script.event_count);
+		EXPECT_CALL(script, init()).Times(0);
+		EXPECT_CALL(script, update()).Times(0);
+		behaviorscript.active = false;
+		system.update();
+	}
+
+	{
+		InSequence seq;
+
+		EXPECT_CALL(script, init()).Times(1);
+		EXPECT_CALL(script, update()).Times(1);
+		behaviorscript.active = true;
+		system.update();
+	}
 }
diff --git a/src/test/ScriptTest.h b/src/test/ScriptTest.h
new file mode 100644
index 0000000..1bbfdd3
--- /dev/null
+++ b/src/test/ScriptTest.h
@@ -0,0 +1,31 @@
+#pragma once
+
+#include <gmock/gmock.h>
+#include <gtest/gtest.h>
+
+#include <crepe/api/BehaviorScript.h>
+#include <crepe/api/Script.h>
+#include <crepe/manager/ComponentManager.h>
+#include <crepe/system/ScriptSystem.h>
+
+class ScriptTest : public testing::Test {
+protected:
+	crepe::Mediator mediator;
+
+public:
+	crepe::ComponentManager component_manager{mediator};
+	crepe::ScriptSystem system{mediator};
+
+	class MyScript : public crepe::Script {
+		// NOTE: explicitly stating `public:` is not required on actual scripts
+
+	public:
+		MOCK_METHOD(void, init, (), (override));
+		MOCK_METHOD(void, update, (), (override));
+	};
+
+	crepe::OptionalRef<crepe::BehaviorScript> behaviorscript;
+	crepe::OptionalRef<MyScript> script;
+
+	virtual void SetUp();
+};