fix(tests): harden factory override checks and keep redirect handling explicit

Use explicit single-or-none descriptor removal (throws if duplicates are present) for DbContext options, DbConnection, DatabaseMigrationService, and EnsureCreatedHostedService. Keep schema creation serialized via semaphore. Update FunctionalTests to use CreateClientWithoutAutoRedirect so manual redirect handling remains intentional.

Author: BenjaminMichaelis

EssentialCSharp.Web.Tests/WebApplicationFactory.cs

@@ -16,7 +16,8 @@ namespace EssentialCSharp.Web.Tests;
 public sealed class WebApplicationFactory : TestWebApplicationFactory<Program>
 {
     private static readonly SemaphoreSlim SchemaInitializationGate = new(1, 1);
-    // One GUID per factory instance → each factory gets its own isolated in-memory database.
+    // One GUID per factory instance (field, not computed property) ensures each factory
+    // gets its own isolated in-memory database and keeps a stable connection string.
     private readonly string _sqlConnectionString =
         $"DataSource=file:{Guid.NewGuid():N}?mode=memory&cache=shared";
 
@@ -28,34 +29,24 @@ protected override void ConfigureWebHost(IWebHostBuilder builder)
     {
         builder.ConfigureServices(services =>
         {
-            for (int i = services.Count - 1; i >= 0; i--)
-            {
-                if (services[i].ServiceType ==
-                    typeof(IDbContextOptionsConfiguration<EssentialCSharpWebContext>))
-                {
-                    services.RemoveAt(i);
-                }
-            }
+            RemoveSingleOrNone(
+                services,
+                descriptor => descriptor.ServiceType ==
+                    typeof(IDbContextOptionsConfiguration<EssentialCSharpWebContext>),
+                "IDbContextOptionsConfiguration<EssentialCSharpWebContext>");
 
-            for (int i = services.Count - 1; i >= 0; i--)
-            {
-                if (services[i].ServiceType == typeof(DbConnection))
-                {
-                    services.RemoveAt(i);
-                }
-            }
+            RemoveSingleOrNone(
+                services,
+                descriptor => descriptor.ServiceType == typeof(DbConnection),
+                nameof(DbConnection));
 
             // Remove DatabaseMigrationService: it calls MigrateAsync which conflicts
             // with EnsureCreated() used below for the in-memory SQLite test database.
-            for (int i = services.Count - 1; i >= 0; i--)
-            {
-                ServiceDescriptor descriptor = services[i];
-                if (descriptor.ServiceType == typeof(IHostedService) &&
-                    descriptor.ImplementationType == typeof(DatabaseMigrationService))
-                {
-                    services.RemoveAt(i);
-                }
-            }
+            RemoveSingleOrNone(
+                services,
+                descriptor => descriptor.ServiceType == typeof(IHostedService) &&
+                    descriptor.ImplementationType == typeof(DatabaseMigrationService),
+                nameof(DatabaseMigrationService));
 
             // Open a keep-alive connection to prevent the shared-cache in-memory database from
             // being dropped when per-scope connections are disposed between requests.
@@ -81,15 +72,11 @@ protected override void ConfigureWebHost(IWebHostBuilder builder)
             });
 
             // Ensure schema exists before any hosted service that reads from the database.
-            for (int i = services.Count - 1; i >= 0; i--)
-            {
-                ServiceDescriptor descriptor = services[i];
-                if (descriptor.ServiceType == typeof(IHostedService) &&
-                    descriptor.ImplementationType == typeof(EnsureCreatedHostedService))
-                {
-                    services.RemoveAt(i);
-                }
-            }
+            RemoveSingleOrNone(
+                services,
+                descriptor => descriptor.ServiceType == typeof(IHostedService) &&
+                    descriptor.ImplementationType == typeof(EnsureCreatedHostedService),
+                nameof(EnsureCreatedHostedService));
 
             ServiceDescriptor ensureCreatedDescriptor =
                 ServiceDescriptor.Singleton<IHostedService, EnsureCreatedHostedService>();
@@ -127,6 +114,32 @@ protected override void Dispose(bool disposing)
         base.Dispose(disposing);
     }
 
+    private static void RemoveSingleOrNone(
+        IServiceCollection services,
+        Func<ServiceDescriptor, bool> predicate,
+        string descriptorName)
+    {
+        List<int> matchIndexes = [];
+        for (int i = 0; i < services.Count; i++)
+        {
+            if (predicate(services[i]))
+            {
+                matchIndexes.Add(i);
+            }
+        }
+
+        if (matchIndexes.Count > 1)
+        {
+            throw new InvalidOperationException(
+                $"Expected at most one '{descriptorName}' registration but found {matchIndexes.Count}.");
+        }
+
+        if (matchIndexes.Count == 1)
+        {
+            services.RemoveAt(matchIndexes[0]);
+        }
+    }
+
     private sealed class EnsureCreatedHostedService(IServiceProvider serviceProvider) : IHostedService
     {
         public async Task StartAsync(CancellationToken cancellationToken)