test: 添加 D3D12 引擎测试框架

- 修复 engine/CMakeLists.txt 路径问题
- 在 tests/D3D12_engine/test/ 创建测试框架
- 添加基础测试夹具 D3D12TestFixture
- 添加 13 个基础测试用例
- 所有测试通过

tests/D3D12_engine/test/fixtures/D3D12TestFixture.h

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <gtest/gtest.h>
+#include <d3d12.h>
+#include <dxgi1_4.h>
+#include <wrl/client.h>
+
+#include "XCEngine/RHI/D3D12/D3D12Device.h"
+#include "XCEngine/RHI/D3D12/D3D12CommandQueue.h"
+#include "XCEngine/RHI/D3D12/D3D12CommandAllocator.h"
+#include "XCEngine/RHI/D3D12/D3D12CommandList.h"
+#include "XCEngine/RHI/D3D12/D3D12Fence.h"
+
+using namespace Microsoft::WRL;
+
+class D3D12TestFixture : public ::testing::Test {
+protected:
+    static void SetUpTestSuite();
+    static void TearDownTestSuite();
+
+    void SetUp() override;
+    void TearDown() override;
+
+    ID3D12Device* GetDevice() { return mDevice.Get(); }
+    ID3D12CommandQueue* GetCommandQueue() { return mCommandQueue.Get(); }
+    ID3D12CommandList* GetCommandList() { return mCommandList.Get(); }
+    ID3D12CommandAllocator* GetCommandAllocator() { return mCommandAllocator.Get(); }
+
+    void WaitForGPU();
+
+private:
+    static ComPtr<ID3D12Device> mDevice;
+    ComPtr<ID3D12CommandQueue> mCommandQueue;
+    ComPtr<ID3D12CommandAllocator> mCommandAllocator;
+    ComPtr<ID3D12CommandList> mCommandList;
+};