refactor: Consolidate handler unit test setup using a shared base class and aggregate factory.

Author: aalmada

tests/BookStore.ApiService.UnitTests/AggregateFactory.cs

@@ -0,0 +1,36 @@
+using System.Reflection;
+
+namespace BookStore.ApiService.UnitTests;
+
+/// <summary>
+/// Domain-neutral factory to create and hydrate aggregates for testing purposes.
+/// This mimics how Marten rehydrates aggregates from the event stream.
+/// </summary>
+public static class AggregateFactory
+{
+    public static T Hydrate<T>(params object[] events) where T : class
+    {
+        var aggregate = (T)Activator.CreateInstance(typeof(T), true)!;
+        var type = typeof(T);
+
+        foreach (var @event in events)
+        {
+            // Find the appropriate Apply method for this event type
+            var applyMethod = type.GetMethod("Apply",
+                BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic,
+                [@event.GetType()]);
+
+            if (applyMethod != null)
+            {
+                _ = applyMethod.Invoke(aggregate, [@event]);
+            }
+            else
+            {
+                throw new InvalidOperationException(
+                    $"Aggregate {type.Name} does not have an Apply method for event type {@event.GetType().Name}");
+            }
+        }
+
+        return aggregate;
+    }
+}

tests/BookStore.ApiService.UnitTests/GlobalUsings.cs

@@ -1 +1,2 @@
 global using BookStore.Shared.Models;
+global using NSubstitute;

tests/BookStore.ApiService.UnitTests/Handlers/AuthorHandlerTests.cs

@@ -2,18 +2,11 @@
 using BookStore.ApiService.Commands;
 using BookStore.ApiService.Events;
 using BookStore.ApiService.Handlers.Authors;
-using BookStore.ApiService.Infrastructure;
-using BookStore.Shared.Models;
-using Marten;
 using Microsoft.AspNetCore.Http;
-using Microsoft.Extensions.Caching.Hybrid;
-using Microsoft.Extensions.Logging;
-using Microsoft.Extensions.Options;
-using NSubstitute;
 
 namespace BookStore.ApiService.UnitTests.Handlers;
 
-public class AuthorHandlerTests
+public class AuthorHandlerTests : HandlerTestBase
 {
     [Test]
     [Category("Unit")]
@@ -25,24 +18,14 @@ public async Task CreateAuthorHandler_ShouldStartStreamWithAuthorAddedEvent()
             new Dictionary<string, AuthorTranslationDto> { ["en"] = new AuthorTranslationDto("Uncle Bob") }
         );
 
-        var session = Substitute.For<IDocumentSession>();
-        _ = session.CorrelationId.Returns("test-correlation-id");
-
-        var localizationOptions = Options.Create(new LocalizationOptions
-        {
-            DefaultCulture = "en",
-            SupportedCultures = ["en"]
-        });
-
         // Act
-        var result = await AuthorHandlers.Handle(command, session, localizationOptions, Substitute.For<HybridCache>(),
-            Substitute.For<ILogger>());
+        var result = await AuthorHandlers.Handle(command, Session, LocalizationOptions, Cache, Logger);
 
         // Assert
         _ = await Assert.That(result).IsNotNull();
-        _ = session.Events.Received(1).StartStream<AuthorAggregate>(
+        _ = Session.Events.Received(1).StartStream<AuthorAggregate>(
             command.Id,
-            Arg.Is<AuthorAdded>(e =>
+            Arg.Is<AuthorAdded>((AuthorAdded e) =>
                 e.Name == "Robert C. Martin"));
     }
 
@@ -59,21 +42,12 @@ public async Task CreateAuthorHandler_WithInvalidCulture_ShouldReturnBadRequest(
             new Dictionary<string, AuthorTranslationDto> { [invalidCulture] = new AuthorTranslationDto("Uncle Bob") }
         );
 
-        var session = Substitute.For<IDocumentSession>();
-        var localizationOptions = Options.Create(new LocalizationOptions
-        {
-            DefaultCulture = "en",
-            SupportedCultures = ["en"]
-        });
-
         // Act
-        var result = await AuthorHandlers.Handle(command, session, localizationOptions, Substitute.For<HybridCache>(),
-            Substitute.For<ILogger>());
+        var result = await AuthorHandlers.Handle(command, Session, LocalizationOptions, Cache, Logger);
 
         // Assert
-        // Assert
-        _ = await Assert.That(result).IsAssignableTo<Microsoft.AspNetCore.Http.IStatusCodeHttpResult>();
-        var badRequestResult = (Microsoft.AspNetCore.Http.IStatusCodeHttpResult)result;
+        _ = await Assert.That(result).IsAssignableTo<IStatusCodeHttpResult>();
+        var badRequestResult = (IStatusCodeHttpResult)result;
         _ = await Assert.That(badRequestResult.StatusCode).IsEqualTo(400);
     }
 
@@ -89,33 +63,24 @@ public async Task UpdateAuthorHandler_ShouldAppendAuthorUpdatedEvent()
         )
         { ETag = "test-etag" };
 
-        var session = Substitute.For<IDocumentSession>();
-        var httpContext = new DefaultHttpContext();
-        var httpContextAccessor = Substitute.For<IHttpContextAccessor>();
-        _ = httpContextAccessor.HttpContext.Returns(httpContext);
-
-        var localizationOptions = Options.Create(new LocalizationOptions
-        {
-            DefaultCulture = "en",
-            SupportedCultures = ["en"]
-        });
-
         // Mock Stream State
-        _ = session.Events.FetchStreamStateAsync(command.Id).Returns(new Marten.Events.StreamState { Version = 1 });
+        _ = Session.Events.FetchStreamStateAsync(command.Id).Returns(new Marten.Events.StreamState { Version = 1 });
 
         // Mock Aggregate Load
-        var existingAggregate = CreateAuthorAggregate(command.Id, "Old Name", false);
-        _ = session.Events.AggregateStreamAsync<AuthorAggregate>(command.Id).Returns(existingAggregate);
+        var existingAggregate = AggregateFactory.Hydrate<AuthorAggregate>(
+            new AuthorAdded(command.Id, "Old Name", new Dictionary<string, AuthorTranslation> { ["en"] = new("Bio") },
+                DateTimeOffset.UtcNow));
+        _ = Session.Events.AggregateStreamAsync<AuthorAggregate>(command.Id).Returns(existingAggregate);
 
         // Act
-        var result = await AuthorHandlers.Handle(command, session, httpContextAccessor, localizationOptions,
-            Substitute.For<HybridCache>(), Substitute.For<ILogger>());
+        var result =
+            await AuthorHandlers.Handle(command, Session, HttpContextAccessor, LocalizationOptions, Cache, Logger);
 
         // Assert
         _ = await Assert.That(result).IsTypeOf<Microsoft.AspNetCore.Http.HttpResults.NoContent>();
-        _ = session.Events.Received(1).Append(
+        _ = Session.Events.Received(1).Append(
             command.Id,
-            Arg.Is<AuthorUpdated>(e =>
+            Arg.Is<AuthorUpdated>((AuthorUpdated e) =>
                 e.Name == "Robert C. Martin Updated"));
     }
 
@@ -127,25 +92,21 @@ public async Task SoftDeleteAuthorHandler_ShouldAppendAuthorSoftDeletedEvent()
         var id = Guid.CreateVersion7();
         var command = new SoftDeleteAuthor(id);
 
-        var session = Substitute.For<IDocumentSession>();
-        var httpContext = new DefaultHttpContext();
-        var httpContextAccessor = Substitute.For<IHttpContextAccessor>();
-        _ = httpContextAccessor.HttpContext.Returns(httpContext);
-
         // Mock Stream State
-        _ = session.Events.FetchStreamStateAsync(id).Returns(new Marten.Events.StreamState { Version = 1 });
+        _ = Session.Events.FetchStreamStateAsync(id).Returns(new Marten.Events.StreamState { Version = 1 });
 
         // Mock Aggregate Load
-        var existingAggregate = CreateAuthorAggregate(id, "Author", false);
-        _ = session.Events.AggregateStreamAsync<AuthorAggregate>(id).Returns(existingAggregate);
+        var existingAggregate = AggregateFactory.Hydrate<AuthorAggregate>(
+            new AuthorAdded(id, "Author", new Dictionary<string, AuthorTranslation> { ["en"] = new("Bio") },
+                DateTimeOffset.UtcNow));
+        _ = Session.Events.AggregateStreamAsync<AuthorAggregate>(id).Returns(existingAggregate);
 
         // Act
-        var result = await AuthorHandlers.Handle(command, session, httpContextAccessor, Substitute.For<HybridCache>(),
-            Substitute.For<ILogger>());
+        var result = await AuthorHandlers.Handle(command, Session, HttpContextAccessor, Cache, Logger);
 
         // Assert
         _ = await Assert.That(result).IsTypeOf<Microsoft.AspNetCore.Http.HttpResults.NoContent>();
-        _ = session.Events.Received(1).Append(
+        _ = Session.Events.Received(1).Append(
             id,
             Arg.Is<AuthorSoftDeleted>(e => e.Id == id));
     }
@@ -158,43 +119,23 @@ public async Task RestoreAuthorHandler_ShouldAppendAuthorRestoredEvent()
         var id = Guid.CreateVersion7();
         var command = new RestoreAuthor(id);
 
-        var session = Substitute.For<IDocumentSession>();
-        var httpContext = new DefaultHttpContext();
-        var httpContextAccessor = Substitute.For<IHttpContextAccessor>();
-        _ = httpContextAccessor.HttpContext.Returns(httpContext);
-
         // Mock Stream State
-        _ = session.Events.FetchStreamStateAsync(id).Returns(new Marten.Events.StreamState { Version = 1 });
+        _ = Session.Events.FetchStreamStateAsync(id).Returns(new Marten.Events.StreamState { Version = 1 });
 
         // Mock Aggregate Load - Create DELETED aggregate
-        var existingAggregate = CreateAuthorAggregate(id, "Author", true);
-        _ = session.Events.AggregateStreamAsync<AuthorAggregate>(id).Returns(existingAggregate);
+        var existingAggregate = AggregateFactory.Hydrate<AuthorAggregate>(
+            new AuthorAdded(id, "Author", new Dictionary<string, AuthorTranslation> { ["en"] = new("Bio") },
+                DateTimeOffset.UtcNow),
+            new AuthorSoftDeleted(id, DateTimeOffset.UtcNow));
+        _ = Session.Events.AggregateStreamAsync<AuthorAggregate>(id).Returns(existingAggregate);
 
         // Act
-        var result = await AuthorHandlers.Handle(command, session, httpContextAccessor, Substitute.For<HybridCache>(),
-            Substitute.For<ILogger>());
+        var result = await AuthorHandlers.Handle(command, Session, HttpContextAccessor, Cache, Logger);
 
         // Assert
         _ = await Assert.That(result).IsTypeOf<Microsoft.AspNetCore.Http.HttpResults.NoContent>();
-        _ = session.Events.Received(1).Append(
+        _ = Session.Events.Received(1).Append(
             id,
             Arg.Is<AuthorRestored>(e => e.Id == id));
     }
-
-    static AuthorAggregate CreateAuthorAggregate(Guid id, string name, bool isDeleted)
-    {
-        // Create instance (AuthorAggregate has parameterless constructor but it might be private/internal?)
-        // It's public class, but properties are private set.
-        // Assuming default constructor is accessible or we use Activator.
-        var aggregate = (AuthorAggregate)Activator.CreateInstance(typeof(AuthorAggregate), true)!;
-
-        // Set properties via reflection
-        typeof(AuthorAggregate).GetProperty(nameof(AuthorAggregate.Id))!.SetValue(aggregate, id);
-        typeof(AuthorAggregate).GetProperty(nameof(AuthorAggregate.Name))!.SetValue(aggregate, name);
-        typeof(AuthorAggregate).GetProperty(nameof(AuthorAggregate.Deleted))!.SetValue(aggregate, isDeleted);
-        typeof(AuthorAggregate).GetProperty(nameof(AuthorAggregate.Translations))!.SetValue(aggregate,
-            new Dictionary<string, AuthorTranslation> { ["en"] = new("Bio") });
-
-        return aggregate;
-    }
 }