From 56420d1c05ca214cec81025e0616c1549bc3a210 Mon Sep 17 00:00:00 2001
From: Copilot <th3w1zard1@users.noreply.github.com>
Date: Wed, 10 Jun 2026 23:27:10 -0500
Subject: [PATCH] test: add DialogService and FileSystemService baseline
 coverage

Cover dialog folder helper guards and file watcher dispose/stop safety paths.
---
 .../gui-architecture-deferred.md              |  2 +-
 ...113-test-dialog-filesystem-service-plan.md | 19 +++++++++++
 src/ModSync.Tests/DialogServiceTests.cs       | 32 ++++++++++++++++++
 src/ModSync.Tests/FileSystemServiceTests.cs   | 33 +++++++++++++++++++
 4 files changed, 85 insertions(+), 1 deletion(-)
 create mode 100644 docs/plans/2026-06-04-113-test-dialog-filesystem-service-plan.md
 create mode 100644 src/ModSync.Tests/DialogServiceTests.cs
 create mode 100644 src/ModSync.Tests/FileSystemServiceTests.cs

diff --git a/docs/knowledgebase/gui-architecture-deferred.md b/docs/knowledgebase/gui-architecture-deferred.md
index 84f2c7db..42da44e0 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 DialogServiceTests` / `FileSystemServiceTests` (plan `113`).
 
 **Agent guidance:** Do not add new feature logic inline without a plan; prefer `src/ModSync.GUI/Services/`.
 
diff --git a/docs/plans/2026-06-04-113-test-dialog-filesystem-service-plan.md b/docs/plans/2026-06-04-113-test-dialog-filesystem-service-plan.md
new file mode 100644
index 00000000..cd141299
--- /dev/null
+++ b/docs/plans/2026-06-04-113-test-dialog-filesystem-service-plan.md
@@ -0,0 +1,19 @@
+---
+title: "test: DialogService and FileSystemService basics"
+status: shipped
+pr: pending
+---
+
+# test: DialogService and FileSystemService basics
+
+## Problem
+
+`DialogService` path-folder helper and `FileSystemService` watcher/dispose lifecycle had no dedicated tests.
+
+## Solution
+
+Add `DialogServiceTests` and `FileSystemServiceTests` for constructor validation, empty-path handling, and safe dispose/stop paths.
+
+## Verification
+
+`dotnet test src/ModSync.Tests/ModSync.Tests.csproj --filter "FullyQualifiedName~DialogServiceTests|FullyQualifiedName~FileSystemServiceTests"
diff --git a/src/ModSync.Tests/DialogServiceTests.cs b/src/ModSync.Tests/DialogServiceTests.cs
new file mode 100644
index 00000000..7437ba8d
--- /dev/null
+++ b/src/ModSync.Tests/DialogServiceTests.cs
@@ -0,0 +1,32 @@
+// 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 System;
+using System.Threading.Tasks;
+using Avalonia.Controls;
+using Avalonia.Headless.XUnit;
+using ModSync.Services;
+using Xunit;
+
+namespace ModSync.Tests
+{
+    [Collection(HeadlessTestApp.CollectionName)]
+    public sealed class DialogServiceTests
+    {
+        [Fact(DisplayName = "Constructor rejects null parent window")]
+        public void Constructor_NullParentWindow_Throws()
+        {
+            Assert.Throws<ArgumentNullException>(() => new DialogService(null));
+        }
+
+        [AvaloniaFact(DisplayName = "GetStorageFolderFromPathAsync returns null for empty path")]
+        public async Task GetStorageFolderFromPathAsync_EmptyPath_ReturnsNull()
+        {
+            var service = new DialogService(new Window());
+
+            Assert.Null(await service.GetStorageFolderFromPathAsync(string.Empty));
+            Assert.Null(await service.GetStorageFolderFromPathAsync(null));
+        }
+    }
+}
diff --git a/src/ModSync.Tests/FileSystemServiceTests.cs b/src/ModSync.Tests/FileSystemServiceTests.cs
new file mode 100644
index 00000000..2cf07d43
--- /dev/null
+++ b/src/ModSync.Tests/FileSystemServiceTests.cs
@@ -0,0 +1,33 @@
+// 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.Services;
+using Xunit;
+
+namespace ModSync.Tests
+{
+    public sealed class FileSystemServiceTests
+    {
+        [Fact(DisplayName = "SetupModDirectoryWatcher does not throw when watcher disabled")]
+        public void SetupModDirectoryWatcher_Disabled_DoesNotThrow()
+        {
+            FileSystemService.SetupModDirectoryWatcher("/tmp", _ => { });
+        }
+
+        [Fact(DisplayName = "StopWatcher does not throw on fresh service")]
+        public void StopWatcher_FreshService_DoesNotThrow()
+        {
+            using var service = new FileSystemService();
+            service.StopWatcher();
+        }
+
+        [Fact(DisplayName = "Dispose can be called multiple times")]
+        public void Dispose_MultipleCalls_DoesNotThrow()
+        {
+            var service = new FileSystemService();
+            service.Dispose();
+            service.Dispose();
+        }
+    }
+}