Added tests for versioning

Sample/EventsVersioning/Talk/EventsVersioning.Talk.sln

@@ -2,6 +2,8 @@
 Microsoft Visual Studio Solution File, Format Version 12.00
 Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HotelManagement", "HotelManagement\HotelManagement.csproj", "{8B5F91C2-572B-4B2D-B67B-3EA98584888E}"
 EndProject
+Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "HotelManagement.Tests", "HotelManagement.Tests\HotelManagement.Tests.csproj", "{79C84CFC-D0C4-4341-B262-92A99A372242}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -12,5 +14,9 @@ Global
 		{8B5F91C2-572B-4B2D-B67B-3EA98584888E}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{8B5F91C2-572B-4B2D-B67B-3EA98584888E}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{8B5F91C2-572B-4B2D-B67B-3EA98584888E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{79C84CFC-D0C4-4341-B262-92A99A372242}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{79C84CFC-D0C4-4341-B262-92A99A372242}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{79C84CFC-D0C4-4341-B262-92A99A372242}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{79C84CFC-D0C4-4341-B262-92A99A372242}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 EndGlobal

Sample/EventsVersioning/Talk/HotelManagement.Tests/Downcasters/ChangedStructure.cs

@@ -0,0 +1,82 @@
+using System.Text.Json;
+using FluentAssertions;
+using HotelManagement.GuestStayAccounts;
+
+namespace HotelManagement.Tests.Downcasters;
+
+using V1 = GuestStayAccountEvent;
+
+public class ChangedStructure
+{
+    public record Money(
+        decimal Amount,
+        string Currency = "CHF"
+    );
+
+    public record PaymentRecorded(
+        string GuestStayAccountId,
+        Money Amount,
+        DateTimeOffset RecordedAt
+    );
+
+    public static V1.PaymentRecorded Downcast(
+        PaymentRecorded newEvent
+    )
+    {
+        return new V1.PaymentRecorded(
+            newEvent.GuestStayAccountId,
+            newEvent.Amount.Amount,
+            newEvent.RecordedAt
+        );
+    }
+
+    public static V1.PaymentRecorded Downcast(
+        string newEventJson
+    )
+    {
+        var newEvent = JsonDocument.Parse(newEventJson).RootElement;
+
+        return new V1.PaymentRecorded(
+            newEvent.GetProperty("GuestStayAccountId").GetString()!,
+            newEvent.GetProperty("Amount").GetProperty("Amount").GetDecimal(),
+            newEvent.GetProperty("RecordedAt").GetDateTimeOffset()
+        );
+    }
+
+    [Fact]
+    public void DowncastObjects_Should_BeForwardCompatible()
+    {
+        // Given
+        var newEvent = new PaymentRecorded(
+            Guid.NewGuid().ToString(),
+            new Money((decimal)Random.Shared.NextDouble(), "USD"),
+            DateTimeOffset.Now
+        );
+
+        // When
+        var @event = Downcast(newEvent);
+
+        @event.Should().NotBeNull();
+        @event.GuestStayAccountId.Should().Be(newEvent.GuestStayAccountId);
+        @event.Amount.Should().Be(newEvent.Amount.Amount);
+    }
+
+    [Fact]
+    public void DowncastJson_Should_BeForwardCompatible()
+    {
+        // Given
+        var newEvent = new PaymentRecorded(
+            Guid.NewGuid().ToString(),
+            new Money((decimal)Random.Shared.NextDouble(), "USD"),
+            DateTimeOffset.Now
+        );
+        // When
+        var @event = Downcast(
+            JsonSerializer.Serialize(newEvent)
+        );
+
+        @event.Should().NotBeNull();
+        @event.GuestStayAccountId.Should().Be(newEvent.GuestStayAccountId);
+        @event.Amount.Should().Be(newEvent.Amount.Amount);
+    }
+}

Sample/EventsVersioning/Talk/HotelManagement.Tests/ExplicitSerialization/ExplicitSerializationTests.cs

@@ -0,0 +1,107 @@
+using System.Text.Json;
+using FluentAssertions;
+
+namespace HotelManagement.Tests.ExplicitSerialization;
+
+using static ShoppingCartEvent;
+
+public class ExplicitSerializationTests
+{
+    [Fact]
+    public void ShouldSerializeAndDeserializeEvents()
+    {
+        var shoppingCartId = ShoppingCartId.New();
+        var clientId = ClientId.New();
+
+        var tShirt = ProductId.New();
+        var tShirtPrice = Price.Parse(new Money(Amount.Parse(33), Currency.PLN));
+
+        var shoes = ProductId.New();
+        var shoesPrice = Price.Parse(new Money(Amount.Parse(77), Currency.PLN));
+
+        var events = new ShoppingCartEvent[]
+        {
+            new ShoppingCartOpened(
+                shoppingCartId,
+                clientId
+            ),
+            new ProductItemAddedToShoppingCart(
+                shoppingCartId,
+                new PricedProductItem(tShirt, Quantity.Parse(5), tShirtPrice)
+            ),
+            new ProductItemAddedToShoppingCart(
+                shoppingCartId,
+                new PricedProductItem(shoes, Quantity.Parse(1), shoesPrice)
+            ),
+            new ProductItemRemovedFromShoppingCart(
+                shoppingCartId,
+                new PricedProductItem(tShirt, Quantity.Parse(3), tShirtPrice)
+            ),
+            new ShoppingCartConfirmed(
+                shoppingCartId,
+                LocalDateTime.Parse(DateTimeOffset.UtcNow)
+            )
+        };
+
+        var serde = new ShoppingCartEventsSerde();
+
+        var serializedEvents = events.Select(serde.Serialize);
+
+        var deserializedEvents = serializedEvents.Select(e =>
+            serde.Deserialize(e.EventType, JsonDocument.Parse(e.Data.ToJsonString()))
+        ).ToArray();
+
+        for (var i = 0; i < deserializedEvents.Length; i++)
+        {
+            deserializedEvents[i].Equals(events[i]).Should().BeTrue();
+        }
+    }
+
+
+    [Fact]
+    public void ShouldGetCurrentShoppingCartState()
+    {
+        var shoppingCartId = ShoppingCartId.New();
+        var clientId = ClientId.New();
+
+        var tShirt = ProductId.New();
+        var tShirtPrice = Price.Parse(new Money(Amount.Parse(33), Currency.PLN));
+
+        var shoes = ProductId.New();
+        var shoesPrice = Price.Parse(new Money(Amount.Parse(77), Currency.PLN));
+
+        var events = new ShoppingCartEvent[]
+        {
+            new ShoppingCartOpened(
+                shoppingCartId,
+                clientId
+            ),
+            new ProductItemAddedToShoppingCart(
+                shoppingCartId,
+                new PricedProductItem(tShirt, Quantity.Parse(5), tShirtPrice)
+            ),
+            new ProductItemAddedToShoppingCart(
+                shoppingCartId,
+                new PricedProductItem(shoes, Quantity.Parse(1), shoesPrice)
+            ),
+            new ProductItemRemovedFromShoppingCart(
+                shoppingCartId,
+                new PricedProductItem(tShirt, Quantity.Parse(3), tShirtPrice)
+            ),
+            new ShoppingCartConfirmed(
+                shoppingCartId,
+                LocalDateTime.Parse(DateTimeOffset.UtcNow)
+            )
+        };
+
+        var shoppingCart = events.Aggregate(ShoppingCart.Default, ShoppingCart.Evolve);
+
+        shoppingCart.Id.Should().Be(shoppingCartId);
+        shoppingCart.ClientId.Should().Be(clientId);
+        shoppingCart.Status.Should().Be(ShoppingCartStatus.Confirmed);
+        shoppingCart.ProductItems.Should().HaveCount(2);
+        shoppingCart.ProductItems.Keys.Should().Contain(new[] { tShirt, shoes });
+        shoppingCart.ProductItems[tShirt].Should().Be(Quantity.Parse(2));
+        shoppingCart.ProductItems[shoes].Should().Be(Quantity.Parse(1));
+    }
+}