test the avatar failback

src/Yavsc.Org.Tests/NonRegression/AvatarFallbackTests.cs

@@ -0,0 +1,34 @@
+namespace Yavsc.Org.Tests.NonRegression;
+
+/// <summary>
+/// Non-regression: avatar requests under /avatars must never return 404
+/// for missing files. The pipeline falls back to static defaults under
+/// /images/Users/icon_user*.png.
+/// </summary>
+public class AvatarFallbackTests : IClassFixture<TestWebApplicationFactory>
+{
+    private readonly TestWebApplicationFactory _factory;
+
+    public AvatarFallbackTests(TestWebApplicationFactory factory)
+    {
+        _factory = factory;
+    }
+
+    [Theory]
+    [InlineData("/avatars/user-does-not-exist.png")]
+    [InlineData("/avatars/user-does-not-exist.s.png")]
+    [InlineData("/avatars/user-does-not-exist.xs.png")]
+    public async Task Missing_avatar_file_returns_default_image_instead_of_404(string path)
+    {
+        using var client = _factory.CreateClient();
+        var ct = TestContext.Current.CancellationToken;
+
+        var response = await client.GetAsync(path, ct);
+
+        Assert.Equal(System.Net.HttpStatusCode.OK, response.StatusCode);
+        Assert.Equal("image/png", response.Content.Headers.ContentType?.MediaType);
+
+        var payload = await response.Content.ReadAsByteArrayAsync(ct);
+        Assert.True(payload.Length > 0, $"Expected a non-empty fallback image for {path}.");
+    }
+}