Refactoring and Adding Tests (#58)

* Moving Identity seeding to its own class and method.

* Adding tests for AddItem

* Added catalog api controller and functional tests
Added and cleaned up some comments

* Adding integration tests for OrderRepository

* Getting integration test for order working with inmemory db

tests/IntegrationTests/Repositories/OrderRepositoryTests/GetById.cs

@@ -0,0 +1,46 @@
+using ApplicationCore.Entities.OrderAggregate;
+using Infrastructure.Data;
+using Microsoft.EntityFrameworkCore;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using UnitTests.Builders;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace IntegrationTests.Repositories.OrderRepositoryTests
+{
+    public class GetById
+    {
+        private readonly CatalogContext _catalogContext;
+        private readonly OrderRepository _orderRepository;
+        private OrderBuilder OrderBuilder { get; } = new OrderBuilder();
+        private readonly ITestOutputHelper _output;
+        public GetById(ITestOutputHelper output)
+        {
+            _output = output;
+            var dbOptions = new DbContextOptionsBuilder<CatalogContext>()
+                .UseInMemoryDatabase(databaseName: "TestCatalog")
+                .Options;
+            _catalogContext = new CatalogContext(dbOptions);
+            _orderRepository = new OrderRepository(_catalogContext);
+        }
+
+        [Fact]
+        public void GetsExistingOrder()
+        {
+            var existingOrder = OrderBuilder.WithDefaultValues();
+            _catalogContext.Orders.Add(existingOrder);
+            _catalogContext.SaveChanges();
+            int orderId = existingOrder.Id;
+            _output.WriteLine($"OrderId: {orderId}");
+
+            var orderFromRepo = _orderRepository.GetById(orderId);
+            Assert.Equal(OrderBuilder.TestBuyerId, orderFromRepo.BuyerId);
+
+            // Note: Using InMemoryDatabase OrderItems is available. Will be null if using SQL DB.
+            var firstItem = orderFromRepo.OrderItems.FirstOrDefault();
+            Assert.Equal(OrderBuilder.TestUnits, firstItem.Units);
+        }
+    }
+}