refactor(tests): reorganize tests directory to match engine structure

- Created tests/Core/Asset/ with tests for IResource, ResourceTypes, ResourceHandle, ResourceCache, ResourceDependencyGraph, ResourceGUID
- Created tests/Core/IO/ with tests for IResourceLoader, ResourcePath, ResourceFileSystem, FileArchive, ResourcePackage
- Reorganized tests/Resources/ into subdirectories: Texture/, Mesh/, Material/, Shader/, AudioClip/
- Added CMakeLists.txt for each new test subdirectory
- Fixed Material.h missing ResourceManager.h include (lost during engine refactor)
- tests/Core/CMakeLists.txt updated to include Asset/ and IO/ subdirectories

tests/Core/Asset/test_resource_guid.cpp

@@ -0,0 +1,64 @@
+#include <gtest/gtest.h>
+#include <XCEngine/Core/Asset/ResourceTypes.h>
+#include <XCEngine/Core/Containers/String.h>
+
+using namespace XCEngine::Resources;
+using namespace XCEngine::Containers;
+
+namespace {
+
+TEST(Resources_GUID, DefaultConstructor) {
+    ResourceGUID guid;
+    EXPECT_FALSE(guid.IsValid());
+    EXPECT_EQ(guid.value, 0);
+}
+
+TEST(Resources_GUID, ValueConstructor) {
+    ResourceGUID guid(12345);
+    EXPECT_TRUE(guid.IsValid());
+    EXPECT_EQ(guid.value, 12345);
+}
+
+TEST(Resources_GUID, Generate_FromCString) {
+    ResourceGUID guid1 = ResourceGUID::Generate("textures/player.png");
+    ResourceGUID guid2 = ResourceGUID::Generate("textures/player.png");
+    
+    EXPECT_EQ(guid1, guid2);
+    EXPECT_TRUE(guid1.IsValid());
+}
+
+TEST(Resources_GUID, Generate_FromString) {
+    String path = "models/player.fbx";
+    ResourceGUID guid = ResourceGUID::Generate(path);
+    EXPECT_TRUE(guid.IsValid());
+}
+
+TEST(Resources_GUID, Generate_DifferentPaths) {
+    ResourceGUID guid1 = ResourceGUID::Generate("textures/a.png");
+    ResourceGUID guid2 = ResourceGUID::Generate("textures/b.png");
+    
+    EXPECT_NE(guid1, guid2);
+}
+
+TEST(Resources_GUID, ToString) {
+    ResourceGUID guid(0x1234567890ABCDEF);
+    String str = guid.ToString();
+    
+    EXPECT_EQ(str.Length(), 16u);
+}
+
+TEST(Resources_GUID, MakeResourceGUID_Helper) {
+    ResourceGUID guid = MakeResourceGUID("test/path");
+    EXPECT_TRUE(guid.IsValid());
+}
+
+TEST(Resources_GUID, EqualityOperators) {
+    ResourceGUID guid1(100);
+    ResourceGUID guid2(100);
+    ResourceGUID guid3(200);
+    
+    EXPECT_TRUE(guid1 == guid2);
+    EXPECT_TRUE(guid1 != guid3);
+}
+
+} // namespace