Fix resize() with non-default constructor + test

Vector.h

@@ -133,7 +133,7 @@ class Vector {
     // Resize the size of the vector to the given new_size
     // If this decreases the size, some elements are deleted
     // If this increases the size, some default-constructed elements are added
-    void resize(unsigned int new_size) {
+    void resize(unsigned int new_size, const T &padder = T()) {
         int difference = new_size - size();
 
         if (difference > 0) {
@@ -143,7 +143,7 @@ class Vector {
 
             // Add additional default-constructed items
             for (int i = 0; i < difference; i++) {
-                data[element_count + i] = T();
+                new (data + element_count + i) T(padder);
             }
         } else if (difference < 0) {
             // Call the destructor on all excess items
@@ -160,15 +160,26 @@ class Vector {
     }
 
   private:
-    unsigned int capacity;
+    unsigned int capacity; // Number of T objects the Vector could hold
-    unsigned int element_count;
+    unsigned int
+        element_count; // Number of T objects the Vector currently holds
     T *data;
 
-    bool is_using_excessive_memory() {
+    // Return a sensible capacity for the given size (including some
+    // padding).
+    unsigned int get_capacity_for_size(unsigned int size) {
+        return size * 2 + 5;
+    }
+
+    // Return true if the Vector is holding much more memory (capacity) than it
+    // currently needs (element_count).
+    inline bool is_using_excessive_memory() {
         return 10 + element_count * 2 < capacity;
     }
 
-    bool new_size_exceeds_capacity(unsigned int new_size) {
+    // Return true if the passed new_size would cause the Vector to exceed the
+    // current capacity (meaning it must be expanded with `reallocate` first).
+    inline bool new_size_exceeds_capacity(unsigned int new_size) {
         return new_size > capacity;
     }
 
@@ -182,10 +193,4 @@ class Vector {
 
         data = new_data;
     }
-
-    // Return a sensible capacity for the given size (including some
-    // padding).
-    unsigned int get_capacity_for_size(unsigned int size) {
-        return size * 2 + 5;
-    }
 };

test.cpp

@@ -256,5 +256,15 @@ SCENARIO("Non-default constructor", "[vector]") {
                 REQUIRE(non_default_vector[0].a == 1);
             }
         }
+
+        WHEN("Creating a vector and resizing it") {
+            Vector<NonDefault> non_default_vector;
+
+            non_default_vector.resize(50, NonDefault(42));
+
+            THEN("The new elements should correspond to the passed padder") {
+                REQUIRE(non_default_vector[49].a == 42);
+            }
+        }
     }
 }