Added tests for mutable aggregate

Workshops/IntroductionToEventSourcing/07-BusinessLogic.Slimmed/Mutable/Aggregate.cs

@@ -1,14 +1,32 @@
 namespace IntroductionToEventSourcing.BusinessLogic.Slimmed.Mutable;
 
-public abstract class Aggregate
+public interface IAggregate
 {
-    public Guid Id { get; protected set; } = default!;
+    public void Evolve(object @event);
 
-    private readonly Queue<object> uncommittedEvents = new();
+    object[] DequeueUncommittedEvents();
+}
+
+public abstract class Aggregate<TEvent>: IAggregate
+{
+    public Guid Id { get; protected set; }
+
+    private readonly Queue<TEvent> uncommittedEvents = new();
+
+    public virtual void Evolve(TEvent @event) { }
+
+    void IAggregate.Evolve(object @event)
+    {
+        if (@event is not TEvent typed)
+            return;
+
+        Evolve(typed);
+    }
 
-    public virtual void Evolve(object @event) { }
+    object[] IAggregate.DequeueUncommittedEvents() =>
+        DequeueUncommittedEvents().Cast<object>().ToArray();
 
-    public object[] DequeueUncommittedEvents()
+    public TEvent[] DequeueUncommittedEvents()
     {
         var dequeuedEvents = uncommittedEvents.ToArray();
 
@@ -17,8 +35,9 @@ public object[] DequeueUncommittedEvents()
         return dequeuedEvents;
     }
 
-    protected void Enqueue(object @event)
+    protected void Enqueue(TEvent @event)
     {
         uncommittedEvents.Enqueue(@event);
+        Evolve(@event);
     }
 }