Adding unit tests

Services/ItemService.cs

@@ -17,22 +17,22 @@ public class ItemService
         _items = db.GetCollection<Item>("Items");
     }
 
-    public async Task CreateAsync(Item item)
+    public virtual async Task CreateAsync(Item item)
     {
         await _items.InsertOneAsync(item);
     }
 
-    public async Task<List<Item>> GetByLocationAsync(string locationId)
+    public virtual async Task<List<Item>> GetByLocationAsync(string locationId)
     {
         return await _items.Find(i => i.LocationId == locationId).ToListAsync();
     }
 
-    public async Task<Item> GetByIdAsync(string id)
+    public virtual async Task<Item> GetByIdAsync(string id)
     {
         return await _items.Find(i => i.Id == id).FirstOrDefaultAsync();
     }
 
-    public async Task UpdateAsync(Item item)
+    public virtual async Task UpdateAsync(Item item)
     {
         await _items.ReplaceOneAsync(i => i.Id == item.Id, item);
     }