Adding more unit tests and fixing the last errors

Juliet/include/Core/Container/Vector.h

@@ -13,6 +13,7 @@ namespace Juliet
       public:
         VectorArena()
           : First(nullptr)
+          , Last(nullptr)
           , Count(0)
           , Stride(sizeof(Type))
         {
@@ -21,6 +22,27 @@ namespace Juliet
 
         ~VectorArena() { ArenaRelease(Arena); }
 
+        VectorArena(const VectorArena&)
+          : Arena(nullptr)
+          , First(nullptr)
+          , Last(nullptr)
+          , Count(0)
+          , Stride(sizeof(Type))
+        {
+            Assert(false, "Copying VectorArena is not allowed");
+        }
+        VectorArena(VectorArena&&) noexcept
+          : Arena(nullptr)
+          , First(nullptr)
+          , Last(nullptr)
+          , Count(0)
+          , Stride(sizeof(Type))
+        {
+            Assert(false, "Moving VectorArena is not allowed");
+        }
+        void operator=(const VectorArena&) { Assert(false, "Copying VectorArena is not allowed"); }
+        void operator=(VectorArena&&) noexcept { Assert(false, "Moving VectorArena is not allowed"); }
+
         void PushBack(Type&& value)
         {
             Type* entry = ArenaPushStruct<Type>(Arena);
@@ -46,13 +68,20 @@ namespace Juliet
             Swap(Last, elementAdr);
             --Last;
             --Count;
+
+            if (Count == 0)
+            {
+                First = Last = nullptr;
+            }
+
             ArenaPop(Arena, Stride);
         }
 
         void Clear()
         {
             ArenaClear(Arena);
-            Count = 0;
+            First = Last = nullptr;
+            Count        = 0;
         }
 
         // C++ Accessors for loop supports and Index based access

Juliet/src/Core/HAL/Display/DisplayDevice.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <Core/Common/NonNullPtr.h>
+#include <Core/Container/Vector.h>
 #include <Core/HAL/Display/Window.h>
 
 namespace Juliet
@@ -29,7 +30,8 @@ namespace Juliet
         void (*PumpEvents)(NonNullPtr<DisplayDevice> self);
 
         // TODO : Use vector
-        Window* MainWindow = nullptr;
+        VectorArena<Window*> Windows;
+        Window*              MainWindow = nullptr;
     };
 
     struct DisplayDeviceFactory

Juliet/src/UnitTest/Container/VectorUnitTest.cpp

@@ -2,33 +2,54 @@
 #if JULIET_DEBUG
 
 #include <algorithm>
-
 #include <Core/Common/CoreUtils.h>
 #include <Core/Container/Vector.h>
 
 namespace Juliet
 {
+    namespace
+    {
+        template <typename T>
+        inline void VerifyVectorState(const VectorArena<T>& vec, size_t expectedCount)
+        {
+            Assert(vec.Size() == expectedCount);
+
+            if (expectedCount == 0)
+            {
+                Assert(vec.begin() == nullptr);
+                Assert(vec.end() == nullptr);
+            }
+            else
+            {
+                Assert(vec.begin() != nullptr);
+                Assert(vec.end() == vec.begin() + expectedCount);
+            }
+        }
+    } // namespace
+
     void VectorUnitTest()
     {
-        // Test 1: Integer VectorArena - Basic PushBack and Access
+        // Test 1: Integer VectorArena
         {
             VectorArena<int> vec;
-            Assert(vec.Size() == 0);
+            VerifyVectorState(vec, 0);
-            Assert(vec.begin() == vec.end());
 
             vec.PushBack(10);
-            Assert(vec.Size() == 1);
+            VerifyVectorState(vec, 1);
             Assert(vec[0] == 10);
             Assert(*vec.begin() == 10);
+            Assert(*(vec.end() - 1) == 10);
 
             vec.PushBack(20);
-            Assert(vec.Size() == 2);
+            VerifyVectorState(vec, 2);
             Assert(vec[0] == 10);
             Assert(vec[1] == 20);
+            Assert(*(vec.end() - 1) == 20);
 
             vec.PushBack(30);
-            Assert(vec.Size() == 3);
+            VerifyVectorState(vec, 3);
             Assert(vec[2] == 30);
+            Assert(*(vec.end() - 1) == 30);
 
             // Test Iteration
             int sum = 0;
@@ -45,24 +66,24 @@ namespace Juliet
             vec.PushBack(10);
             vec.PushBack(20);
             vec.PushBack(30);
+            VerifyVectorState(vec, 3);
 
-            // Initial: [10, 20, 30]
+            // Remove index 0 (value 10). Should swap with Last (30).
-            // Remove index 0 (value 10). Should swap with Last (30) and pop last.
-            // Expected: [30, 20]
             vec.RemoveAtFast(0);
-            Assert(vec.Size() == 2);
+            VerifyVectorState(vec, 2);
             Assert(vec[0] == 30);
             Assert(vec[1] == 20);
+            Assert(*(vec.end() - 1) == 20);
 
-            // Remove index 1 (value 20). Last is 20. Swap 20 with 20.
+            // Remove index 1 (value 20).
-            // Expected: [30]
             vec.RemoveAtFast(1);
-            Assert(vec.Size() == 1);
+            VerifyVectorState(vec, 1);
             Assert(vec[0] == 30);
+            Assert(*(vec.end() - 1) == 30);
 
             // Remove remaining element
             vec.RemoveAtFast(0);
-            Assert(vec.Size() == 0);
+            VerifyVectorState(vec, 0);
         }
 
         // Test 3: Clear and Reuse
@@ -70,19 +91,18 @@ namespace Juliet
             VectorArena<int> vec;
             vec.PushBack(100);
             vec.PushBack(200);
-            Assert(vec.Size() == 2);
+            VerifyVectorState(vec, 2);
 
             vec.Clear();
-            Assert(vec.Size() == 0);
+            VerifyVectorState(vec, 0);
-            Assert(vec.begin() == vec.end());
 
-            // Should be able to push again
             vec.PushBack(300);
-            Assert(vec.Size() == 1);
+            VerifyVectorState(vec, 1);
             Assert(vec[0] == 300);
+            Assert(*(vec.end() - 1) == 300);
         }
 
-        // Test 4: Struct VectorArena (Testing Move Semantics and Complex Types)
+        // Test 4: Struct VectorArena
         {
             struct TestItem
             {
@@ -97,25 +117,60 @@ namespace Juliet
             };
 
             VectorArena<TestItem> vec;
-            TestItem              test{ 1, 1.0f };
+            VerifyVectorState(vec, 0);
-            vec.PushBack(std::move(test));
+
+            vec.PushBack({ 1, 1.0f });
             vec.PushBack({ 2, 2.0f });
             vec.PushBack({ 3, 3.0f });
+            VerifyVectorState(vec, 3);
 
-            Assert(vec.Size() == 3);
+            // Remove middle element (index 1)
-            Assert(vec[0].A == 1);
-            Assert(vec[1].A == 2);
-
-            // Remove middle element (index 1, value {2, 2.0f})
-            // Should swap with last ({3, 3.0f})
-            // Result: [{1, 1.0f}, {3, 3.0f}]
             vec.RemoveAtFast(1);
-            Assert(vec.Size() == 2);
+            VerifyVectorState(vec, 2);
-            // Use operator== to verify entire struct including float
             Assert(vec[0] == (TestItem{ 1, 1.0f }));
             Assert(vec[1] == (TestItem{ 3, 3.0f }));
         }
+
+        // Test 5: Add 2, Remove 2 -> Expect nullptr
+        {
+            VectorArena<int> vec;
+            vec.PushBack(1);
+            vec.PushBack(2);
+            VerifyVectorState(vec, 2);
+
+            vec.RemoveAtFast(0);
+            vec.RemoveAtFast(0);
+            VerifyVectorState(vec, 0);
+        }
+
+        // Test 6: Volume Test (100 items)
+        {
+            VectorArena<int> vec;
+            VerifyVectorState(vec, 0);
+
+            // Push 100 items
+            for (int i = 0; i < 100; ++i)
+            {
+                vec.PushBack(static_cast<int>(i));
+            }
+            VerifyVectorState(vec, 100);
+
+            // Verify content
+            for (int i = 0; i < 100; ++i)
+            {
+                Assert(vec[static_cast<size_t>(i)] == i);
+            }
+
+            // Remove 50 items from front (causing swaps)
+            for (int i = 0; i < 50; ++i)
+            {
+                vec.RemoveAtFast(0);
+            }
+            VerifyVectorState(vec, 50);
+
+            vec.Clear();
+            VerifyVectorState(vec, 0);
+        }
     }
 } // namespace Juliet
-
 #endif