Engine: 实现 Components 和 Scene 模块，包含完整单元测试

新增 Components 模块:
- Component 基类 (生命周期、启用状态管理)
- TransformComponent (本地/世界空间变换、矩阵缓存、父子层级)
- GameObject (组件管理、父子层级、激活状态、静态查找)

新增 Scene 模块:
- Scene (场景管理、对象创建销毁、查找、生命周期)
- SceneManager (单例模式、多场景管理、场景切换)

新增测试:
- test_component.cpp (12 个测试)
- test_transform_component.cpp (35 个测试)
- test_game_object.cpp (26 个测试)
- test_scene.cpp (20 个测试)
- test_scene_manager.cpp (17 个测试)

所有测试均已编译通过。

tests/Components/CMakeLists.txt

@@ -0,0 +1,29 @@
+cmake_minimum_required(VERSION 3.15)
+
+project(XCEngine_ComponentsTests)
+
+set(COMPONENTS_TEST_SOURCES
+    test_component.cpp
+    test_transform_component.cpp
+    test_game_object.cpp
+)
+
+add_executable(xcengine_components_tests ${COMPONENTS_TEST_SOURCES})
+
+if(MSVC)
+    set_target_properties(xcengine_components_tests PROPERTIES
+        LINK_FLAGS "/NODEFAULTLIB:libcpmt.lib /NODEFAULTLIB:libcmt.lib"
+    )
+endif()
+
+target_link_libraries(xcengine_components_tests PRIVATE
+    XCEngine
+    GTest::gtest
+    GTest::gtest_main
+)
+
+target_include_directories(xcengine_components_tests PRIVATE
+    ${CMAKE_SOURCE_DIR}/engine/include
+)
+
+add_test(NAME ComponentTests COMMAND xcengine_components_tests)

tests/Components/test_component.cpp

@@ -0,0 +1,110 @@
+#include <gtest/gtest.h>
+#include <XCEngine/Components/Component.h>
+#include <XCEngine/Components/GameObject.h>
+
+using namespace XCEngine::Components;
+
+namespace {
+
+class TestComponent : public Component {
+public:
+    TestComponent() = default;
+    explicit TestComponent(const std::string& name) : m_customName(name) {}
+
+    std::string GetName() const override { 
+        return m_customName.empty() ? "TestComponent" : m_customName; 
+    }
+
+    bool m_awakeCalled = false;
+    bool m_startCalled = false;
+    bool m_updateCalled = false;
+    bool m_onEnableCalled = false;
+    bool m_onDisableCalled = false;
+    bool m_onDestroyCalled = false;
+
+    void Awake() override { m_awakeCalled = true; }
+    void Start() override { m_startCalled = true; }
+    void Update(float deltaTime) override { m_updateCalled = true; }
+    void OnEnable() override { m_onEnableCalled = true; }
+    void OnDisable() override { m_onDisableCalled = true; }
+    void OnDestroy() override { m_onDestroyCalled = true; }
+
+private:
+    std::string m_customName;
+};
+
+TEST(Component_Test, DefaultConstructor) {
+    TestComponent comp;
+    EXPECT_EQ(comp.GetName(), "TestComponent");
+}
+
+TEST(Component_Test, GetGameObject_ReturnsNullptr_WhenNotAttached) {
+    TestComponent comp;
+    EXPECT_EQ(comp.GetGameObject(), nullptr);
+}
+
+TEST(Component_Test, IsEnabled_DefaultTrue) {
+    TestComponent comp;
+    EXPECT_TRUE(comp.IsEnabled());
+}
+
+TEST(Component_Test, SetEnabled_TrueToFalse) {
+    TestComponent comp;
+    EXPECT_TRUE(comp.IsEnabled());
+    comp.SetEnabled(false);
+    EXPECT_FALSE(comp.IsEnabled());
+}
+
+TEST(Component_Test, SetEnabled_FalseToTrue) {
+    TestComponent comp;
+    comp.SetEnabled(false);
+    EXPECT_FALSE(comp.IsEnabled());
+    comp.SetEnabled(true);
+    EXPECT_TRUE(comp.IsEnabled());
+}
+
+TEST(Component_Test, Lifecycle_AwakeCalled) {
+    TestComponent comp;
+    comp.Awake();
+    EXPECT_TRUE(comp.m_awakeCalled);
+}
+
+TEST(Component_Test, Lifecycle_StartCalled) {
+    TestComponent comp;
+    comp.Start();
+    EXPECT_TRUE(comp.m_startCalled);
+}
+
+TEST(Component_Test, Lifecycle_UpdateCalled) {
+    TestComponent comp;
+    comp.Update(0.016f);
+    EXPECT_TRUE(comp.m_updateCalled);
+}
+
+TEST(Component_Test, Lifecycle_OnEnableCalled_WhenEnabling) {
+    TestComponent comp;
+    comp.SetEnabled(false);
+    comp.SetEnabled(true);
+    EXPECT_TRUE(comp.m_onEnableCalled);
+}
+
+TEST(Component_Test, Lifecycle_OnDisableCalled_WhenDisabling) {
+    TestComponent comp;
+    comp.SetEnabled(false);
+    EXPECT_TRUE(comp.m_onDisableCalled);
+}
+
+TEST(Component_Test, Lifecycle_OnDestroyCalled) {
+    TestComponent comp;
+    comp.OnDestroy();
+    EXPECT_TRUE(comp.m_onDestroyCalled);
+}
+
+TEST(Component_Test, SetEnabled_NoCallback_WhenStateUnchanged) {
+    TestComponent comp;
+    comp.SetEnabled(true);
+    EXPECT_FALSE(comp.m_onEnableCalled);
+    EXPECT_FALSE(comp.m_onDisableCalled);
+}
+
+} // namespace

tests/Components/test_game_object.cpp

@@ -0,0 +1,277 @@
+#include <gtest/gtest.h>
+#include <XCEngine/Components/GameObject.h>
+#include <XCEngine/Components/TransformComponent.h>
+#include <XCEngine/Scene/Scene.h>
+#include <XCEngine/Math/Vector3.h>
+
+using namespace XCEngine::Components;
+using namespace XCEngine::Math;
+
+namespace {
+
+class TestComponent : public Component {
+public:
+    TestComponent() = default;
+    explicit TestComponent(const std::string& name) : m_customName(name) {}
+
+    std::string GetName() const override {
+        return m_customName.empty() ? "TestComponent" : m_customName;
+    }
+
+    bool m_awakeCalled = false;
+    bool m_startCalled = false;
+    bool m_updateCalled = false;
+
+    void Awake() override { m_awakeCalled = true; }
+    void Start() override { m_startCalled = true; }
+    void Update(float deltaTime) override { m_updateCalled = true; }
+
+private:
+    std::string m_customName;
+};
+
+class GameObjectTest : public ::testing::Test {
+protected:
+    void SetUp() override {
+        testScene = std::make_unique<Scene>("TestScene");
+    }
+
+    std::unique_ptr<Scene> testScene;
+};
+
+TEST(GameObject_Test, DefaultConstructor_DefaultValues) {
+    GameObject go;
+    
+    EXPECT_EQ(go.GetName(), "GameObject");
+    EXPECT_TRUE(go.IsActive());
+    EXPECT_EQ(go.GetID(), GameObject::INVALID_ID);
+}
+
+TEST(GameObject_Test, NamedConstructor) {
+    GameObject go("TestObject");
+    
+    EXPECT_EQ(go.GetName(), "TestObject");
+}
+
+TEST(GameObject_Test, AddComponent_Single) {
+    GameObject go;
+    
+    TestComponent* comp = go.AddComponent<TestComponent>();
+    
+    EXPECT_NE(comp, nullptr);
+    EXPECT_EQ(go.GetComponent<TestComponent>(), comp);
+}
+
+TEST(GameObject_Test, AddComponent_Multiple) {
+    GameObject go;
+    
+    TestComponent* comp1 = go.AddComponent<TestComponent>();
+    TestComponent* comp2 = go.AddComponent<TestComponent>();
+    
+    EXPECT_NE(comp1, nullptr);
+    EXPECT_NE(comp2, nullptr);
+    EXPECT_NE(comp1, comp2);
+}
+
+TEST(GameObject_Test, AddComponent_TransformComponent) {
+    GameObject go;
+    
+    TransformComponent* tc = go.GetTransform();
+    
+    EXPECT_NE(tc, nullptr);
+    EXPECT_EQ(tc->GetName(), "Transform");
+}
+
+TEST(GameObject_Test, GetComponent_Exists) {
+    GameObject go;
+    TestComponent* comp = go.AddComponent<TestComponent>();
+    
+    TestComponent* found = go.GetComponent<TestComponent>();
+    
+    EXPECT_EQ(found, comp);
+}
+
+TEST(GameObject_Test, GetComponent_NotExists) {
+    GameObject go;
+    
+    TestComponent* found = go.GetComponent<TestComponent>();
+    
+    EXPECT_EQ(found, nullptr);
+}
+
+TEST(GameObject_Test, GetComponents_Multiple) {
+    GameObject go;
+    go.AddComponent<TestComponent>();
+    go.AddComponent<TestComponent>();
+    go.AddComponent<TestComponent>();
+    
+    std::vector<TestComponent*> comps = go.GetComponents<TestComponent>();
+    
+    EXPECT_EQ(comps.size(), 3u);
+}
+
+TEST(GameObject_Test, GetTransform_ReturnsTransform) {
+    GameObject go;
+    
+    TransformComponent* tc = go.GetTransform();
+    
+    EXPECT_NE(tc, nullptr);
+}
+
+TEST(GameObject_Test, SetParent_WithWorldPosition) {
+    GameObject parent("Parent");
+    GameObject child("Child");
+    
+    parent.GetTransform()->SetLocalPosition(Vector3(1.0f, 0.0f, 0.0f));
+    child.GetTransform()->SetLocalPosition(Vector3(2.0f, 0.0f, 0.0f));
+    
+    child.SetParent(&parent, true);
+    
+    Vector3 childWorldPos = child.GetTransform()->GetPosition();
+    EXPECT_NEAR(childWorldPos.x, 2.0f, 0.001f);
+}
+
+TEST(GameObject_Test, SetParent_WithoutWorldPosition) {
+    GameObject parent("Parent");
+    GameObject child("Child");
+    
+    parent.GetTransform()->SetLocalPosition(Vector3(1.0f, 0.0f, 0.0f));
+    child.GetTransform()->SetLocalPosition(Vector3(2.0f, 0.0f, 0.0f));
+    
+    child.SetParent(&parent, false);
+    
+    Vector3 childWorldPos = child.GetTransform()->GetPosition();
+    EXPECT_NEAR(childWorldPos.x, 3.0f, 0.001f);
+}
+
+TEST(GameObject_Test, GetChild_ValidIndex) {
+    GameObject parent("Parent");
+    GameObject child("Child");
+    
+    child.SetParent(&parent);
+    
+    GameObject* found = parent.GetChild(0);
+    
+    EXPECT_EQ(found, &child);
+}
+
+TEST(GameObject_Test, GetChild_InvalidIndex) {
+    GameObject parent("Parent");
+    
+    GameObject* found = parent.GetChild(0);
+    
+    EXPECT_EQ(found, nullptr);
+}
+
+TEST(GameObject_Test, GetChildren_ReturnsAllChildren) {
+    GameObject parent("Parent");
+    GameObject child1("Child1");
+    GameObject child2("Child2");
+    
+    child1.SetParent(&parent);
+    child2.SetParent(&parent);
+    
+    std::vector<GameObject*> children = parent.GetChildren();
+    
+    EXPECT_EQ(children.size(), 2u);
+}
+
+TEST(GameObject_Test, DetachChildren) {
+    GameObject parent("Parent");
+    GameObject child("Child");
+    
+    child.SetParent(&parent);
+    EXPECT_EQ(parent.GetChildCount(), 1u);
+    
+    parent.DetachChildren();
+    
+    EXPECT_EQ(parent.GetChildCount(), 0u);
+}
+
+TEST(GameObject_Test, IsActive_DefaultTrue) {
+    GameObject go;
+    
+    EXPECT_TRUE(go.IsActive());
+}
+
+TEST(GameObject_Test, SetActive_False) {
+    GameObject go;
+    
+    go.SetActive(false);
+    
+    EXPECT_FALSE(go.IsActive());
+}
+
+TEST(GameObject_Test, IsActiveInHierarchy_True) {
+    GameObject parent("Parent");
+    GameObject child("Child");
+    
+    child.SetParent(&parent);
+    
+    EXPECT_TRUE(child.IsActiveInHierarchy());
+}
+
+TEST(GameObject_Test, IsActiveInHierarchy_FalseWhenParentInactive) {
+    GameObject parent("Parent");
+    GameObject child("Child");
+    
+    child.SetParent(&parent);
+    parent.SetActive(false);
+    
+    EXPECT_FALSE(child.IsActiveInHierarchy());
+}
+
+TEST(GameObject_Test, Lifecycle_Awake) {
+    GameObject go;
+    TestComponent* comp = go.AddComponent<TestComponent>();
+    
+    go.Awake();
+    
+    EXPECT_TRUE(comp->m_awakeCalled);
+}
+
+TEST(GameObject_Test, Lifecycle_Start) {
+    GameObject go;
+    TestComponent* comp = go.AddComponent<TestComponent>();
+    
+    go.Start();
+    
+    EXPECT_TRUE(comp->m_startCalled);
+}
+
+TEST(GameObject_Test, Lifecycle_Update) {
+    GameObject go;
+    TestComponent* comp = go.AddComponent<TestComponent>();
+    
+    go.Update(0.016f);
+    
+    EXPECT_TRUE(comp->m_updateCalled);
+}
+
+TEST_F(GameObjectTest, Find_Exists) {
+    GameObject* go = testScene->CreateGameObject("TestObject");
+    
+    GameObject* found = GameObject::Find("TestObject");
+    
+    EXPECT_NE(found, nullptr);
+    EXPECT_EQ(found->GetName(), "TestObject");
+}
+
+TEST(GameObject_Test, Find_NotExists) {
+    GameObject* found = GameObject::Find("NonExistent");
+    
+    EXPECT_EQ(found, nullptr);
+}
+
+TEST(GameObject_Test, GetChildCount) {
+    GameObject parent("Parent");
+    GameObject child1("Child1");
+    GameObject child2("Child2");
+    
+    child1.SetParent(&parent);
+    child2.SetParent(&parent);
+    
+    EXPECT_EQ(parent.GetChildCount(), 2u);
+}
+
+} // namespace

tests/Components/test_transform_component.cpp

@@ -0,0 +1,306 @@
+#include <gtest/gtest.h>
+#include <XCEngine/Components/TransformComponent.h>
+#include <XCEngine/Math/Math.h>
+
+using namespace XCEngine::Components;
+using namespace XCEngine::Math;
+
+namespace {
+
+class TransformComponentTest : public ::testing::Test {
+protected:
+    void SetUp() override {
+        transform = std::make_unique<TransformComponent>();
+    }
+
+    std::unique_ptr<TransformComponent> transform;
+};
+
+TEST(TransformComponent_Test, DefaultConstructor_IdentityValues) {
+    TransformComponent tc;
+    
+    EXPECT_EQ(tc.GetLocalPosition(), Vector3::Zero());
+    EXPECT_TRUE(tc.GetLocalRotation().Dot(Quaternion::Identity()) > 0.99f);
+    EXPECT_EQ(tc.GetLocalScale(), Vector3::One());
+}
+
+TEST(TransformComponent_Test, LocalPosition_GetSet) {
+    TransformComponent tc;
+    Vector3 pos(1.0f, 2.0f, 3.0f);
+    
+    tc.SetLocalPosition(pos);
+    
+    EXPECT_EQ(tc.GetLocalPosition(), pos);
+}
+
+TEST(TransformComponent_Test, LocalRotation_GetSet) {
+    TransformComponent tc;
+    Quaternion rot = Quaternion::FromAxisAngle(Vector3::Up(), PI * 0.5f);
+    
+    tc.SetLocalRotation(rot);
+    
+    EXPECT_TRUE(tc.GetLocalRotation().Dot(rot) > 0.99f);
+}
+
+TEST(TransformComponent_Test, LocalScale_GetSet) {
+    TransformComponent tc;
+    Vector3 scale(2.0f, 2.0f, 2.0f);
+    
+    tc.SetLocalScale(scale);
+    
+    EXPECT_EQ(tc.GetLocalScale(), scale);
+}
+
+TEST(TransformComponent_Test, LocalEulerAngles_GetSet) {
+    TransformComponent tc;
+    Vector3 eulers(45.0f, 30.0f, 60.0f);
+    
+    tc.SetLocalEulerAngles(eulers);
+    Vector3 result = tc.GetLocalEulerAngles();
+    
+    EXPECT_NEAR(result.x, eulers.x, 1.0f);
+    EXPECT_NEAR(result.y, eulers.y, 1.0f);
+    EXPECT_NEAR(result.z, eulers.z, 1.0f);
+}
+
+TEST(TransformComponent_Test, WorldPosition_NoParent_EqualsLocal) {
+    TransformComponent tc;
+    Vector3 pos(1.0f, 2.0f, 3.0f);
+    
+    tc.SetLocalPosition(pos);
+    
+    EXPECT_EQ(tc.GetPosition(), pos);
+}
+
+TEST(TransformComponent_Test, WorldPosition_WithParent) {
+    TransformComponent parent;
+    TransformComponent child;
+    
+    parent.SetLocalPosition(Vector3(1.0f, 0.0f, 0.0f));
+    child.SetParent(&parent);
+    child.SetLocalPosition(Vector3(2.0f, 0.0f, 0.0f));
+    
+    Vector3 worldPos = child.GetPosition();
+    
+    EXPECT_NEAR(worldPos.x, 3.0f, 0.001f);
+}
+
+TEST(TransformComponent_Test, WorldRotation_WithParent) {
+    TransformComponent parent;
+    TransformComponent child;
+    
+    parent.SetLocalRotation(Quaternion::FromAxisAngle(Vector3::Up(), PI * 0.5f));
+    child.SetParent(&parent);
+    child.SetLocalRotation(Quaternion::FromAxisAngle(Vector3::Up(), PI * 0.5f));
+    
+    Quaternion worldRot = child.GetRotation();
+    
+    EXPECT_TRUE(worldRot.Magnitude() > 0.0f);
+}
+
+TEST(TransformComponent_Test, WorldScale_WithParent) {
+    TransformComponent parent;
+    TransformComponent child;
+    
+    parent.SetLocalScale(Vector3(2.0f, 2.0f, 2.0f));
+    child.SetParent(&parent);
+    child.SetLocalScale(Vector3(2.0f, 2.0f, 2.0f));
+    
+    Vector3 worldScale = child.GetScale();
+    
+    EXPECT_NEAR(worldScale.x, 4.0f, 0.001f);
+    EXPECT_NEAR(worldScale.y, 4.0f, 0.001f);
+    EXPECT_NEAR(worldScale.z, 4.0f, 0.001f);
+}
+
+TEST(TransformComponent_Test, DirectionVectors_Forward) {
+    TransformComponent tc;
+    
+    Vector3 forward = tc.GetForward();
+    
+    EXPECT_NEAR(forward.z, 1.0f, 0.001f);
+}
+
+TEST(TransformComponent_Test, DirectionVectors_Right) {
+    TransformComponent tc;
+    
+    Vector3 right = tc.GetRight();
+    
+    EXPECT_NEAR(right.x, 1.0f, 0.001f);
+}
+
+TEST(TransformComponent_Test, DirectionVectors_Up) {
+    TransformComponent tc;
+    
+    Vector3 up = tc.GetUp();
+    
+    EXPECT_NEAR(up.y, 1.0f, 0.001f);
+}
+
+TEST(TransformComponent_Test, LocalToWorldMatrix_Identity) {
+    TransformComponent tc;
+    
+    const Matrix4x4& matrix = tc.GetLocalToWorldMatrix();
+    
+    EXPECT_EQ(matrix[0][0], 1.0f);
+    EXPECT_EQ(matrix[1][1], 1.0f);
+    EXPECT_EQ(matrix[2][2], 1.0f);
+    EXPECT_EQ(matrix[3][3], 1.0f);
+}
+
+TEST(TransformComponent_Test, LocalToWorldMatrix_Translation) {
+    TransformComponent tc;
+    Vector3 pos(5.0f, 10.0f, 15.0f);
+    tc.SetLocalPosition(pos);
+    
+    const Matrix4x4& matrix = tc.GetLocalToWorldMatrix();
+    
+    EXPECT_NEAR(matrix[0][3], pos.x, 0.001f);
+    EXPECT_NEAR(matrix[1][3], pos.y, 0.001f);
+    EXPECT_NEAR(matrix[2][3], pos.z, 0.001f);
+}
+
+TEST(TransformComponent_Test, LocalToWorldMatrix_Rotation) {
+    TransformComponent tc;
+    tc.SetLocalRotation(Quaternion::FromAxisAngle(Vector3::Up(), PI * 0.5f));
+    
+    const Matrix4x4& matrix = tc.GetLocalToWorldMatrix();
+    
+    EXPECT_NEAR(matrix[0][0], 0.0f, 0.001f);
+    EXPECT_NEAR(matrix[0][2], 1.0f, 0.001f);
+}
+
+TEST(TransformComponent_Test, LookAt_Target) {
+    TransformComponent tc;
+    Vector3 target(10.0f, 0.0f, 0.0f);
+    
+    tc.SetPosition(Vector3::Zero());
+    tc.LookAt(target);
+    
+    Vector3 forward = tc.GetForward();
+    EXPECT_NEAR(forward.x, 1.0f, 0.1f);
+}
+
+TEST(TransformComponent_Test, Rotate_Eulers) {
+    TransformComponent tc;
+    
+    tc.Rotate(Vector3(90.0f, 0.0f, 0.0f));
+    
+    Vector3 eulers = tc.GetLocalEulerAngles();
+    EXPECT_TRUE(eulers.x > 80.0f);
+}
+
+TEST(TransformComponent_Test, Translate_Self) {
+    TransformComponent tc;
+    Vector3 initialPos = tc.GetLocalPosition();
+    
+    tc.Translate(Vector3(1.0f, 2.0f, 3.0f), Space::Self);
+    
+    Vector3 newPos = tc.GetLocalPosition();
+    EXPECT_NEAR(newPos.x, initialPos.x + 1.0f, 0.001f);
+    EXPECT_NEAR(newPos.y, initialPos.y + 2.0f, 0.001f);
+    EXPECT_NEAR(newPos.z, initialPos.z + 3.0f, 0.001f);
+}
+
+TEST(TransformComponent_Test, TransformPoint_LocalToWorld) {
+    TransformComponent tc;
+    tc.SetLocalPosition(Vector3(1.0f, 2.0f, 3.0f));
+    
+    Vector3 localPoint(1.0f, 0.0f, 0.0f);
+    Vector3 worldPoint = tc.TransformPoint(localPoint);
+    
+    EXPECT_NEAR(worldPoint.x, 2.0f, 0.001f);
+    EXPECT_NEAR(worldPoint.y, 2.0f, 0.001f);
+    EXPECT_NEAR(worldPoint.z, 3.0f, 0.001f);
+}
+
+TEST(TransformComponent_Test, InverseTransformPoint_WorldToLocal) {
+    TransformComponent tc;
+    tc.SetLocalPosition(Vector3(1.0f, 2.0f, 3.0f));
+    
+    Vector3 worldPoint(2.0f, 2.0f, 3.0f);
+    Vector3 localPoint = tc.InverseTransformPoint(worldPoint);
+    
+    EXPECT_NEAR(localPoint.x, 1.0f, 0.001f);
+    EXPECT_NEAR(localPoint.y, 0.0f, 0.001f);
+    EXPECT_NEAR(localPoint.z, 0.0f, 0.001f);
+}
+
+TEST(TransformComponent_Test, TransformDirection) {
+    TransformComponent tc;
+    tc.SetLocalRotation(Quaternion::FromAxisAngle(Vector3::Up(), PI * 0.5f));
+    
+    Vector3 localDir(1.0f, 0.0f, 0.0f);
+    Vector3 worldDir = tc.TransformDirection(localDir);
+    
+    EXPECT_NEAR(worldDir.z, -1.0f, 0.1f);
+}
+
+TEST(TransformComponent_Test, SetDirty_PropagatesToChildren) {
+    TransformComponent parent;
+    TransformComponent child;
+    child.SetParent(&parent);
+    
+    parent.SetLocalPosition(Vector3(1.0f, 2.0f, 3.0f));
+    child.SetLocalPosition(Vector3(1.0f, 0.0f, 0.0f));
+    
+    Vector3 childWorldPosBefore = child.GetPosition();
+    
+    parent.SetLocalPosition(Vector3(10.0f, 0.0f, 0.0f));
+    Vector3 childWorldPosAfter = child.GetPosition();
+    
+    EXPECT_NE(childWorldPosBefore.x, childWorldPosAfter.x);
+}
+
+TEST(TransformComponent_Test, GetChildCount_Empty) {
+    TransformComponent tc;
+    EXPECT_EQ(tc.GetChildCount(), 0u);
+}
+
+TEST(TransformComponent_Test, GetChild_InvalidIndex) {
+    TransformComponent tc;
+    EXPECT_EQ(tc.GetChild(0), nullptr);
+}
+
+TEST(TransformComponent_Test, DetachChildren) {
+    TransformComponent parent;
+    TransformComponent child1;
+    TransformComponent child2;
+    
+    child1.SetParent(&parent);
+    child2.SetParent(&parent);
+    
+    EXPECT_EQ(parent.GetChildCount(), 2u);
+    
+    parent.DetachChildren();
+    
+    EXPECT_EQ(parent.GetChildCount(), 0u);
+}
+
+TEST(TransformComponent_Test, SetAsFirstSibling) {
+    TransformComponent parent;
+    TransformComponent child1;
+    TransformComponent child2;
+    
+    child1.SetParent(&parent);
+    child2.SetParent(&parent);
+    
+    child2.SetAsFirstSibling();
+    
+    EXPECT_EQ(child2.GetSiblingIndex(), 0);
+}
+
+TEST(TransformComponent_Test, SetAsLastSibling) {
+    TransformComponent parent;
+    TransformComponent child1;
+    TransformComponent child2;
+    
+    child1.SetParent(&parent);
+    child2.SetParent(&parent);
+    
+    child1.SetAsLastSibling();
+    
+    EXPECT_EQ(child1.GetSiblingIndex(), 1);
+}
+
+} // namespace