diff --git a/tests/Jellyfin.Plugin.Multilang.Tests/ItemsProxySortingTests.cs b/tests/Jellyfin.Plugin.Multilang.Tests/ItemsProxySortingTests.cs
new file mode 100644
index 0000000..fd2bed7
--- /dev/null
+++ b/tests/Jellyfin.Plugin.Multilang.Tests/ItemsProxySortingTests.cs
@@ -0,0 +1,106 @@
+using System.Globalization;
+using System.Text.Json.Nodes;
+using Jellyfin.Plugin.Multilang.Configuration;
+using Jellyfin.Plugin.Multilang.Services;
+
+namespace Jellyfin.Plugin.Multilang.Tests;
+
+public sealed class ItemsProxySortingTests
+{
+    [Fact]
+    public void GetSortArticlesUsesBuiltInLocaleFallback()
+    {
+        var articles = ItemsProxySorting.GetSortArticles(new SortArticleCatalog(), [], "sv-FI");
+
+        Assert.Equal(["en", "ett"], articles);
+    }
+
+    [Fact]
+    public void GetSortArticlesUsesConfiguredLanguageFallback()
+    {
+        var articles = ItemsProxySorting.GetSortArticles(
+            new SortArticleCatalog(),
+            [new SortArticleEntry { Language = "en", Articles = "one, two" }],
+            "en-CA");
+
+        Assert.Equal(["one", "two"], articles);
+    }
+
+    [Fact]
+    public void GetSortArticlesPrefersConfiguredExactLocale()
+    {
+        var articles = ItemsProxySorting.GetSortArticles(
+            new SortArticleCatalog(),
+            [
+                new SortArticleEntry { Language = "en", Articles = "language" },
+                new SortArticleEntry { Language = "en-GB", Articles = "exact" }
+            ],
+            "en-GB");
+
+        Assert.Equal(["exact"], articles);
+    }
+
+    [Fact]
+    public void ApplySortsByTitleAfterLeadingArticles()
+    {
+        var root = ItemsRoot("The Matrix", "A Beautiful Mind", "Avatar");
+
+        ItemsProxySorting.Apply(
+            root,
+            new ItemsProxyControls("SortName", "Ascending", "", 0, 0, "en-US", ""),
+            CultureInfo.GetCultureInfo("en-US"),
+            ["a", "an", "the"]);
+
+        Assert.Equal(["Avatar", "A Beautiful Mind", "The Matrix"], ItemNames(root));
+    }
+
+    [Fact]
+    public void ApplyPadsNumbersDuringTitleSort()
+    {
+        var root = ItemsRoot("Movie 10", "Movie 2", "Movie 1");
+
+        ItemsProxySorting.Apply(
+            root,
+            new ItemsProxyControls("SortName", "Ascending", "", 0, 0, "en-US", ""),
+            CultureInfo.GetCultureInfo("en-US"),
+            []);
+
+        Assert.Equal(["Movie 1", "Movie 2", "Movie 10"], ItemNames(root));
+    }
+
+    [Fact]
+    public void ApplyFiltersAndSlicesAfterLocalSort()
+    {
+        var root = ItemsRoot("The Matrix", "Magnolia", "A Monster Calls", "Avatar");
+
+        ItemsProxySorting.Apply(
+            root,
+            new ItemsProxyControls("SortName", "Ascending", "M", 1, 1, "en-US", ""),
+            CultureInfo.GetCultureInfo("en-US"),
+            ["a", "an", "the"]);
+
+        Assert.Equal(["The Matrix"], ItemNames(root));
+        Assert.Equal(3, root["TotalRecordCount"]!.GetValue<int>());
+        Assert.Equal(1, root["StartIndex"]!.GetValue<int>());
+    }
+
+    private static JsonObject ItemsRoot(params string[] names)
+    {
+        var items = new JsonArray();
+        foreach (var name in names)
+            items.Add(new JsonObject { ["Name"] = name, ["SortName"] = name });
+
+        return new JsonObject
+        {
+            ["Items"] = items,
+            ["TotalRecordCount"] = names.Length,
+            ["StartIndex"] = 0
+        };
+    }
+
+    private static string[] ItemNames(JsonObject root)
+        => root["Items"]!.AsArray()
+            .OfType<JsonObject>()
+            .Select(item => item["Name"]!.GetValue<string>())
+            .ToArray();
+}