[2pts] Write unit tests — items and inventory

[github-actions]

Description

Create comprehensive unit tests for item system and player inventory.

Depends on: Item subclasses and Player issues

Test Coverage

Item Subclass Tests

• Weapon.Use(): Verify damage bonus applied correctly
• Armor.Use(): Verify defense bonus applied correctly
• Potion.Use(): Verify healing applied correctly
• Potion healing capped at MaxHealth

Player Inventory Tests

• AddItem() adds item to inventory
• RemoveItem() removes item from inventory
• UseItem() applies item effect and removes from inventory
• Inventory state changes verified

LootResolver Tests

• Test with injected seed for deterministic drops
• Verify drop probability calculations
• Verify Dragon always drops at least one item
• Verify Gold equals GoldReward

Requirements

• Use xUnit testing framework
• Use seeded Random for loot tests
• Test edge cases (full health, empty inventory, etc.)
• All tests must pass in CI pipeline

Acceptance Criteria

• Test class for Item subclasses
• Weapon.Use() damage bonus tested
• Armor.Use() defense bonus tested
• Potion.Use() healing tested
• Potion healing capped at MaxHealth verified
• Test class for Player inventory operations
• AddItem() tested
• RemoveItem() tested
• UseItem() tested
• Inventory state changes verified
• Test class for LootResolver
• Tested with injected seed
• Drop probability logic verified
• Dragon loot guarantee tested
• Gold amount verification tested
• All tests pass in CI
• Tests follow naming conventions