Swap in an in-memory file storage provider for the API specs

docs/web/testing.md

@@ -257,7 +257,8 @@ API.Specs/
 │   └── ApiGeneralSteps.cs              # Shared/general step definitions
 ├── Mocks/
 │   ├── MockEmailDispatcher.cs          # Substitutes Features.Emails' IEmailDispatcher
-│   └── MockEmailProvider.cs            # Substitutes Features.Emails' IEmailProvider
+│   ├── MockEmailProvider.cs            # Substitutes Features.Emails' IEmailProvider
+│   └── MockFileStorageProvider.cs      # Substitutes Features.ImageUploads' IFileStorageProvider
 └── TestApiFactory.cs                   # Test server setup (swaps in the mocks above)
 ```
 

web/backend/API/API.Specs/Mocks/MockFileStorageProvider.cs

@@ -0,0 +1,55 @@
+using Features.ImageUploads.Services;
+
+namespace API.Specs.Mocks;
+
+/// <summary>
+///     Test double for <see cref="IFileStorageProvider" /> that records uploads in memory, so specs can
+///     exercise photo-backed features without object storage.
+/// </summary>
+public class MockFileStorageProvider : IFileStorageProvider
+{
+    private readonly List<string> _keys = [];
+    private readonly Dictionary<string, byte[]> _objects = new();
+
+    public IReadOnlyCollection<string> UploadedKeys => _keys.ToList();
+
+    /// <summary>The key of the most recent upload.</summary>
+    /// <exception cref="InvalidOperationException">Thrown when nothing has been uploaded yet.</exception>
+    public string LastUploadedKey =>
+        _keys.Count > 0
+            ? _keys[^1]
+            : throw new InvalidOperationException("no file has been uploaded");
+
+    public Task UploadAsync(
+        string key,
+        Stream content,
+        string contentType,
+        CancellationToken cancellationToken = default
+    )
+    {
+        using MemoryStream buffer = new();
+        content.CopyTo(buffer);
+
+        if (!_objects.ContainsKey(key))
+            _keys.Add(key);
+
+        _objects[key] = buffer.ToArray();
+        return Task.CompletedTask;
+    }
+
+    public Task DeleteAsync(string key, CancellationToken cancellationToken = default)
+    {
+        _objects.Remove(key);
+        _keys.Remove(key);
+        return Task.CompletedTask;
+    }
+
+    /// <summary>
+    ///     Stands in for a signed download URL: an absolute URL on a host the object store would serve,
+    ///     carrying the key in its path, so specs can assert the shape callers actually receive.
+    /// </summary>
+    public string GetPresignedUrl(string key, TimeSpan expiresIn)
+    {
+        return $"https://storage.test/{key}?X-Amz-Expires={(int)expiresIn.TotalSeconds}";
+    }
+}

web/backend/API/API.Specs/TestApiFactory.cs

@@ -1,6 +1,7 @@
 using API.Core;
 using API.Specs.Mocks;
 using Features.Emails.Services;
+using Features.ImageUploads.Services;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc.Testing;
 using Microsoft.Extensions.DependencyInjection;
@@ -32,6 +33,15 @@ internal class TestApiFactory : WebApplicationFactory<Program>
                 services.Remove(emailDispatcherDescriptor);
 
             services.AddScoped<IEmailDispatcher, MockEmailDispatcher>();
+
+            ServiceDescriptor? fileStorageDescriptor = services.SingleOrDefault(d =>
+                d.ServiceType == typeof(IFileStorageProvider)
+            );
+
+            if (fileStorageDescriptor != null)
+                services.Remove(fileStorageDescriptor);
+
+            services.AddSingleton<IFileStorageProvider, MockFileStorageProvider>();
         });
     }
 }