From c8e6f2ee36852af3bb45544de3f701ea7397c313 Mon Sep 17 00:00:00 2001
From: Copilot <th3w1zard1@users.noreply.github.com>
Date: Wed, 10 Jun 2026 23:11:25 -0500
Subject: [PATCH] test: add TierFilterItem and SelectionFilterItem model
 coverage

Cover display text and selection state used by mod list filter sidebar models.
---
 .../gui-architecture-deferred.md              |  2 +-
 ...-06-04-112-test-filter-item-models-plan.md | 19 +++++
 src/ModSync.Tests/FilterItemModelTests.cs     | 78 +++++++++++++++++++
 3 files changed, 98 insertions(+), 1 deletion(-)
 create mode 100644 docs/plans/2026-06-04-112-test-filter-item-models-plan.md
 create mode 100644 src/ModSync.Tests/FilterItemModelTests.cs

diff --git a/docs/knowledgebase/gui-architecture-deferred.md b/docs/knowledgebase/gui-architecture-deferred.md
index 84f2c7db..a8e6a36f 100644
--- a/docs/knowledgebase/gui-architecture-deferred.md
+++ b/docs/knowledgebase/gui-architecture-deferred.md
@@ -62,7 +62,7 @@ Plans: `docs/plans/2026-06-03-012`, `021`–`029`, `033`–`057`. Surface refere
 | Directory picker init/sync → `SettingsService` | Done | plan `075`, PR pending |
 | Mod context menu + global flyout → `MenuBuilderService` | Pending | plan `072`, PR #120 |
 
-**Headless tests:** `dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter SettingsService` (plan `077`, complements PR #123 picker wiring).
+**Headless tests:** `dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter SettingsService` (plan `077`, complements PR #123 picker wiring); `--filter FilterItemModel` (plan `112`).
 
 **Agent guidance:** Do not add new feature logic inline without a plan; prefer `src/ModSync.GUI/Services/`.
 
diff --git a/docs/plans/2026-06-04-112-test-filter-item-models-plan.md b/docs/plans/2026-06-04-112-test-filter-item-models-plan.md
new file mode 100644
index 00000000..f9094e89
--- /dev/null
+++ b/docs/plans/2026-06-04-112-test-filter-item-models-plan.md
@@ -0,0 +1,19 @@
+---
+title: "test: TierFilterItem and SelectionFilterItem models"
+status: shipped
+pr: pending
+---
+
+# test: TierFilterItem and SelectionFilterItem models
+
+## Problem
+
+Filter sidebar models format tier/category labels and selection state but had no dedicated tests beyond `FilterUIService` integration coverage.
+
+## Solution
+
+Add `FilterItemModelTests` for `DisplayText`, `EffectiveSelection`, and selection toggles.
+
+## Verification
+
+`dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter FilterItemModel
diff --git a/src/ModSync.Tests/FilterItemModelTests.cs b/src/ModSync.Tests/FilterItemModelTests.cs
new file mode 100644
index 00000000..d7b50629
--- /dev/null
+++ b/src/ModSync.Tests/FilterItemModelTests.cs
@@ -0,0 +1,78 @@
+// Copyright 2021-2025 ModSync
+// Licensed under the Business Source License 1.1 (BSL 1.1).
+// See LICENSE.txt file in the project root for full license information.
+
+using ModSync.Models;
+using Xunit;
+
+namespace ModSync.Tests
+{
+    public sealed class FilterItemModelTests
+    {
+        [Fact(DisplayName = "TierFilterItem DisplayText formats name and count")]
+        public void TierFilterItem_DisplayText_FormatsNameAndCount()
+        {
+            var item = new TierFilterItem
+            {
+                Name = "1 - Essential",
+                Count = 3,
+            };
+
+            Assert.Equal("1 - Essential (3)", item.DisplayText);
+        }
+
+        [Fact(DisplayName = "TierFilterItem EffectiveSelection reflects selected or included state")]
+        public void TierFilterItem_EffectiveSelection_ReflectsSelectionState()
+        {
+            var item = new TierFilterItem();
+
+            item.IsIncluded = true;
+            Assert.True(item.EffectiveSelection);
+
+            item.IsIncluded = false;
+            item.IsSelected = true;
+            Assert.True(item.EffectiveSelection);
+
+            item.IsSelected = false;
+            Assert.False(item.EffectiveSelection);
+        }
+
+        [Fact(DisplayName = "TierFilterItem count change updates DisplayText")]
+        public void TierFilterItem_CountChange_UpdatesDisplayText()
+        {
+            var item = new TierFilterItem
+            {
+                Name = "2 - Recommended",
+                Count = 1,
+            };
+
+            item.Count = 5;
+
+            Assert.Equal("2 - Recommended (5)", item.DisplayText);
+        }
+
+        [Fact(DisplayName = "SelectionFilterItem DisplayText formats name and count")]
+        public void SelectionFilterItem_DisplayText_FormatsNameAndCount()
+        {
+            var item = new SelectionFilterItem
+            {
+                Name = "Patch",
+                Count = 2,
+            };
+
+            Assert.Equal("Patch (2)", item.DisplayText);
+        }
+
+        [Fact(DisplayName = "SelectionFilterItem IsSelected toggles independently")]
+        public void SelectionFilterItem_IsSelected_Toggles()
+        {
+            var item = new SelectionFilterItem { IsSelected = false };
+
+            item.IsSelected = true;
+            Assert.True(item.IsSelected);
+
+            item.IsSelected = false;
+            Assert.False(item.IsSelected);
+        }
+    }
+}