diff --git a/SongTidy.Tests/RenameFormatsTests.cs b/SongTidy.Tests/Models/RenameFormatsTests.cs
similarity index 99%
rename from SongTidy.Tests/RenameFormatsTests.cs
rename to SongTidy.Tests/Models/RenameFormatsTests.cs
index a26994c..f346463 100644
--- a/SongTidy.Tests/RenameFormatsTests.cs
+++ b/SongTidy.Tests/Models/RenameFormatsTests.cs
@@ -1,6 +1,6 @@
 using SongTidy.Models;
 
-namespace SongTidy.Tests;
+namespace SongTidy.Tests.Models;
 
 /// <summary>
 /// Contains tests for <see cref="RenameFormats"/>.
diff --git a/SongTidy.Tests/AudioFileScannerTests.cs b/SongTidy.Tests/Services/AudioFileScannerTests.cs
similarity index 76%
rename from SongTidy.Tests/AudioFileScannerTests.cs
rename to SongTidy.Tests/Services/AudioFileScannerTests.cs
index 1dcaa18..02913d1 100644
--- a/SongTidy.Tests/AudioFileScannerTests.cs
+++ b/SongTidy.Tests/Services/AudioFileScannerTests.cs
@@ -2,31 +2,23 @@ using System.IO;
 using System.Linq;
 
 using SongTidy.Services;
+using SongTidy.Tests.TestUtilities;
 
-namespace SongTidy.Tests;
+namespace SongTidy.Tests.Services;
 
 /// <summary>
 /// Contains tests for <see cref="AudioFileScanner"/>.
 /// </summary>
 [TestClass]
 public sealed class AudioFileScannerTests {
-    private string _tempDirectory = string.Empty;
-
-    /// <summary>
-    /// Creates a unique temporary directory for the current test.
-    /// </summary>
-    [TestInitialize]
-    public void Initialize() {
-        _tempDirectory = Path.Combine(Path.GetTempPath(), $"SongTidy Scanner {Guid.NewGuid():N}");
-        Directory.CreateDirectory(_tempDirectory);
-    }
+    private readonly TempDirectory _tempDirectory = new();
 
     /// <summary>
     /// Removes the temporary directory created for the current test.
     /// </summary>
     [TestCleanup]
     public void Cleanup() {
-        Directory.Delete(_tempDirectory, recursive: true);
+        _tempDirectory.Dispose();
     }
 
     /// <summary>
@@ -38,7 +30,7 @@ public sealed class AudioFileScannerTests {
         CreateFile("b.FLAC");
         CreateFile("c.txt");
 
-        IReadOnlyList<string> files = AudioFileScanner.Scan(_tempDirectory);
+        IReadOnlyList<string> files = AudioFileScanner.Scan(_tempDirectory.FullPath);
 
         Assert.HasCount(2, files);
         Assert.IsTrue(files.Any(file => file.EndsWith("a.mp3", StringComparison.OrdinalIgnoreCase)));
@@ -53,7 +45,7 @@ public sealed class AudioFileScannerTests {
         CreateFile("root.mp3");
         CreateFile(Path.Combine("sub", "nested.wav"));
 
-        IReadOnlyList<string> files = AudioFileScanner.Scan(_tempDirectory);
+        IReadOnlyList<string> files = AudioFileScanner.Scan(_tempDirectory.FullPath);
 
         Assert.HasCount(1, files);
         Assert.IsTrue(files[0].EndsWith("root.mp3", StringComparison.OrdinalIgnoreCase));
@@ -64,8 +56,8 @@ public sealed class AudioFileScannerTests {
     /// </summary>
     /// <param name="fileName">The relative file name, which may include a subdirectory.</param>
     private void CreateFile(string fileName) {
-        string path = Path.Combine(_tempDirectory, fileName);
-        string directory = Path.GetDirectoryName(path) ?? _tempDirectory;
+        string path = Path.Combine(_tempDirectory.FullPath, fileName);
+        string directory = Path.GetDirectoryName(path) ?? _tempDirectory.FullPath;
 
         Directory.CreateDirectory(directory);
         File.WriteAllText(path, string.Empty);
diff --git a/SongTidy.Tests/FilenameParserTests.cs b/SongTidy.Tests/Services/FilenameParserTests.cs
similarity index 99%
rename from SongTidy.Tests/FilenameParserTests.cs
rename to SongTidy.Tests/Services/FilenameParserTests.cs
index 637cc93..1d0f77a 100644
--- a/SongTidy.Tests/FilenameParserTests.cs
+++ b/SongTidy.Tests/Services/FilenameParserTests.cs
@@ -1,6 +1,6 @@
 using SongTidy.Services;
 
-namespace SongTidy.Tests;
+namespace SongTidy.Tests.Services;
 
 /// <summary>
 /// Contains tests for <see cref="FilenameParser"/>.
diff --git a/SongTidy.Tests/PlanXmlIOTests.cs b/SongTidy.Tests/Services/PlanXmlIOTests.cs
similarity index 89%
rename from SongTidy.Tests/PlanXmlIOTests.cs
rename to SongTidy.Tests/Services/PlanXmlIOTests.cs
index 68240fb..02e76f6 100644
--- a/SongTidy.Tests/PlanXmlIOTests.cs
+++ b/SongTidy.Tests/Services/PlanXmlIOTests.cs
@@ -6,8 +6,9 @@ using System.Xml.Linq;
 
 using SongTidy.Models;
 using SongTidy.Services;
+using SongTidy.Tests.TestUtilities;
 
-namespace SongTidy.Tests;
+namespace SongTidy.Tests.Services;
 
 /// <summary>
 /// Contains tests for <see cref="PlanXmlIO"/>.
@@ -210,32 +211,27 @@ public sealed class PlanXmlIOTests {
     /// </summary>
     [TestMethod]
     public void SavesAndLoadsFileWithSpacesInPath() {
-        string directory = Path.Combine(Path.GetTempPath(), $"SongTidy Plan Test {Guid.NewGuid():N}");
-        string filePath = Path.Combine(directory, "plan with spaces.xml");
-        Directory.CreateDirectory(directory);
+        using TempDirectory tempDirectory = new();
+        string filePath = Path.Combine(tempDirectory.FullPath, "plan with spaces.xml");
 
-        try {
-            SongPlan plan = CreateSamplePlan();
+        SongPlan plan = CreateSamplePlan();
 
-            PlanXmlIO.Save(plan, filePath);
+        PlanXmlIO.Save(plan, filePath);
 
-            Assert.IsTrue(File.Exists(filePath));
+        Assert.IsTrue(File.Exists(filePath));
 
-            byte[] bytes = File.ReadAllBytes(filePath);
-            Assert.AreEqual((byte)'<', bytes[0]);
+        byte[] bytes = File.ReadAllBytes(filePath);
+        Assert.AreEqual((byte)'<', bytes[0]);
 
-            string xml = Encoding.UTF8.GetString(bytes);
-            Assert.IsTrue(
-                xml.StartsWith("<?xml version=\"1.0\" encoding=\"utf-8\"?>", StringComparison.Ordinal),
-                "The file should be written as UTF-8 without a BOM.");
+        string xml = Encoding.UTF8.GetString(bytes);
+        Assert.IsTrue(
+            xml.StartsWith("<?xml version=\"1.0\" encoding=\"utf-8\"?>", StringComparison.Ordinal),
+            "The file should be written as UTF-8 without a BOM.");
 
-            SongPlan loaded = PlanXmlIO.Load(filePath);
-            Assert.AreEqual(plan.Format, loaded.Format);
-            Assert.HasCount(plan.Items.Count, loaded.Items);
-            AssertPlanItem(plan.Items[0], loaded.Items[0]);
-        } finally {
-            Directory.Delete(directory, recursive: true);
-        }
+        SongPlan loaded = PlanXmlIO.Load(filePath);
+        Assert.AreEqual(plan.Format, loaded.Format);
+        Assert.HasCount(plan.Items.Count, loaded.Items);
+        AssertPlanItem(plan.Items[0], loaded.Items[0]);
     }
 
     #endregion
diff --git a/SongTidy.Tests/RenameValidatorTests.cs b/SongTidy.Tests/Services/RenameValidatorTests.cs
similarity index 94%
rename from SongTidy.Tests/RenameValidatorTests.cs
rename to SongTidy.Tests/Services/RenameValidatorTests.cs
index a94defa..932b451 100644
--- a/SongTidy.Tests/RenameValidatorTests.cs
+++ b/SongTidy.Tests/Services/RenameValidatorTests.cs
@@ -3,31 +3,23 @@ using System.Linq;
 
 using SongTidy.Models;
 using SongTidy.Services;
+using SongTidy.Tests.TestUtilities;
 
-namespace SongTidy.Tests;
+namespace SongTidy.Tests.Services;
 
 /// <summary>
 /// Contains tests for <see cref="RenameValidator"/>.
 /// </summary>
 [TestClass]
 public sealed class RenameValidatorTests {
-    private string _tempDirectory = string.Empty;
-
-    /// <summary>
-    /// Creates a unique temporary directory for the current test.
-    /// </summary>
-    [TestInitialize]
-    public void Initialize() {
-        _tempDirectory = Path.Combine(Path.GetTempPath(), $"SongTidy Validation {Guid.NewGuid():N}");
-        Directory.CreateDirectory(_tempDirectory);
-    }
+    private readonly TempDirectory _tempDirectory = new();
 
     /// <summary>
     /// Removes the temporary directory created for the current test.
     /// </summary>
     [TestCleanup]
     public void Cleanup() {
-        Directory.Delete(_tempDirectory, recursive: true);
+        _tempDirectory.Dispose();
     }
 
     #region Per-entry validation
@@ -105,7 +97,7 @@ public sealed class RenameValidatorTests {
     /// </summary>
     [TestMethod]
     public void ReportsMissingSourceFile() {
-        string sourcePath = Path.Combine(_tempDirectory, "Missing.mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "Missing.mp3");
 
         RenameValidationResult result = Validate(CreateItem(sourcePath, "Title"));
 
@@ -140,8 +132,8 @@ public sealed class RenameValidatorTests {
     [TestMethod]
     public void TreatsSourcePathsAsCaseSensitive() {
         CreateFile("Case.mp3");
-        PlanItem first = CreateItem(Path.Combine(_tempDirectory, "Case.mp3"), "One");
-        PlanItem second = CreateItem(Path.Combine(_tempDirectory, "case.mp3"), "Two");
+        PlanItem first = CreateItem(Path.Combine(_tempDirectory.FullPath, "Case.mp3"), "One");
+        PlanItem second = CreateItem(Path.Combine(_tempDirectory.FullPath, "case.mp3"), "Two");
 
         RenameValidationResult result = Validate(first, second);
 
@@ -283,7 +275,7 @@ public sealed class RenameValidatorTests {
     public void ReportsAllProblemKinds() {
         string sourcePath = CreateFile("A.mp3");
         PlanItem emptyTitle = CreateItem(sourcePath, "");
-        PlanItem missingSource = CreateItem(Path.Combine(_tempDirectory, "Missing.mp3"), "Title");
+        PlanItem missingSource = CreateItem(Path.Combine(_tempDirectory.FullPath, "Missing.mp3"), "Title");
         PlanItem invalidCharacter = CreateItem(sourcePath, "Bad/Title");
 
         RenameValidationResult result = Validate(emptyTitle, missingSource, invalidCharacter);
@@ -319,8 +311,8 @@ public sealed class RenameValidatorTests {
     /// <param name="fileName">The relative file name, which may include a subdirectory.</param>
     /// <returns>The full path of the created file.</returns>
     private string CreateFile(string fileName) {
-        string path = Path.Combine(_tempDirectory, fileName);
-        string directory = Path.GetDirectoryName(path) ?? _tempDirectory;
+        string path = Path.Combine(_tempDirectory.FullPath, fileName);
+        string directory = Path.GetDirectoryName(path) ?? _tempDirectory.FullPath;
 
         Directory.CreateDirectory(directory);
         File.WriteAllText(path, string.Empty);
diff --git a/SongTidy.Tests/TestUtilities/TempDirectory.cs b/SongTidy.Tests/TestUtilities/TempDirectory.cs
new file mode 100644
index 0000000..cca61d4
--- /dev/null
+++ b/SongTidy.Tests/TestUtilities/TempDirectory.cs
@@ -0,0 +1,40 @@
+namespace SongTidy.Tests.TestUtilities;
+
+/// <summary>
+/// Creates a unique temporary directory per test instance and removes it on disposal.
+/// </summary>
+public sealed class TempDirectory : IDisposable {
+    /// <summary>
+    /// Gets the unique directory path managed by this instance.
+    /// </summary>
+    public string FullPath { get; }
+
+    /// <summary>
+    /// Creates a unique temporary directory.
+    /// </summary>
+    public TempDirectory() {
+        FullPath = Path.Combine(Path.GetTempPath(), "songtidy-tests-" + Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(FullPath);
+    }
+
+    /// <summary>
+    /// Deletes the directory tree, retrying once after a short delay.
+    /// </summary>
+    public void Dispose() {
+        try {
+            // SAFETY: Recursive deletion is confined to the GUID-named directory
+            // created by this instance under the OS temp folder.
+            Directory.Delete(FullPath, recursive: true);
+        } catch (IOException) {
+            // A file handle may still be closing; retry once before giving up.
+            Thread.Sleep(100);
+
+            try {
+                // SAFETY: The retry targets the same instance-owned temp directory.
+                Directory.Delete(FullPath, recursive: true);
+            } catch (IOException) {
+                // Leftovers in the OS temp folder are harmless; never fail a test over cleanup.
+            }
+        }
+    }
+}
diff --git a/SongTidy.Tests/MainWindowViewModelTests.cs b/SongTidy.Tests/ViewModels/MainWindowViewModelTests.cs
similarity index 81%
rename from SongTidy.Tests/MainWindowViewModelTests.cs
rename to SongTidy.Tests/ViewModels/MainWindowViewModelTests.cs
index 4b5f232..1127365 100644
--- a/SongTidy.Tests/MainWindowViewModelTests.cs
+++ b/SongTidy.Tests/ViewModels/MainWindowViewModelTests.cs
@@ -3,32 +3,24 @@ using System.Linq;
 
 using SongTidy.Models;
 using SongTidy.Services;
+using SongTidy.Tests.TestUtilities;
 using SongTidy.ViewModels;
 
-namespace SongTidy.Tests;
+namespace SongTidy.Tests.ViewModels;
 
 /// <summary>
 /// Contains tests for <see cref="MainWindowViewModel"/>.
 /// </summary>
 [TestClass]
 public sealed class MainWindowViewModelTests {
-    private string _tempDirectory = string.Empty;
-
-    /// <summary>
-    /// Creates a unique temporary directory for the current test.
-    /// </summary>
-    [TestInitialize]
-    public void Initialize() {
-        _tempDirectory = Path.Combine(Path.GetTempPath(), $"SongTidy ViewModel {Guid.NewGuid():N}");
-        Directory.CreateDirectory(_tempDirectory);
-    }
+    private readonly TempDirectory _tempDirectory = new();
 
     /// <summary>
     /// Removes the temporary directory created for the current test.
     /// </summary>
     [TestCleanup]
     public void Cleanup() {
-        Directory.Delete(_tempDirectory, recursive: true);
+        _tempDirectory.Dispose();
     }
 
     #region Input and merge rules
@@ -39,7 +31,7 @@ public sealed class MainWindowViewModelTests {
     [TestMethod]
     public void AddFilesParsesAndAppendsEntries() {
         MainWindowViewModel viewModel = new();
-        string sourcePath = Path.Combine(_tempDirectory, "A - B (Live).mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "A - B (Live).mp3");
 
         viewModel.AddFiles(new[] { sourcePath });
 
@@ -62,7 +54,7 @@ public sealed class MainWindowViewModelTests {
     [TestMethod]
     public void AddFilesSkipsDuplicatesAndPreservesEdits() {
         MainWindowViewModel viewModel = new();
-        string sourcePath = Path.Combine(_tempDirectory, "A - B.mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "A - B.mp3");
         viewModel.AddFiles(new[] { sourcePath });
         viewModel.Entries[0].Artist = "Edited";
 
@@ -80,8 +72,8 @@ public sealed class MainWindowViewModelTests {
         MainWindowViewModel viewModel = new();
 
         viewModel.AddFiles(new[] {
-            Path.Combine(_tempDirectory, "a.mp3"),
-            Path.Combine(_tempDirectory, "A.mp3"),
+            Path.Combine(_tempDirectory.FullPath, "a.mp3"),
+            Path.Combine(_tempDirectory.FullPath, "A.mp3"),
         });
 
         Assert.HasCount(2, viewModel.Entries);
@@ -93,9 +85,9 @@ public sealed class MainWindowViewModelTests {
     [TestMethod]
     public void AddFilesWithOnlyDuplicatesDoesNotDirty() {
         MainWindowViewModel viewModel = new();
-        string sourcePath = Path.Combine(_tempDirectory, "A.mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "A.mp3");
         viewModel.AddFiles(new[] { sourcePath });
-        viewModel.SavePlan(Path.Combine(_tempDirectory, "plan.xml"));
+        viewModel.SavePlan(Path.Combine(_tempDirectory.FullPath, "plan.xml"));
 
         viewModel.AddFiles(new[] { sourcePath });
 
@@ -113,7 +105,7 @@ public sealed class MainWindowViewModelTests {
         CreateFile("C.txt");
         CreateFile(Path.Combine("sub", "D.wav"));
 
-        viewModel.AddFilesFromFolder(_tempDirectory);
+        viewModel.AddFilesFromFolder(_tempDirectory.FullPath);
 
         Assert.HasCount(2, viewModel.Entries);
     }
@@ -128,9 +120,9 @@ public sealed class MainWindowViewModelTests {
     [TestMethod]
     public void EntryEditMarksDirtyAndRevertingDoesNotClear() {
         MainWindowViewModel viewModel = new();
-        string sourcePath = Path.Combine(_tempDirectory, "A.mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "A.mp3");
         viewModel.AddFiles(new[] { sourcePath });
-        viewModel.SavePlan(Path.Combine(_tempDirectory, "plan.xml"));
+        viewModel.SavePlan(Path.Combine(_tempDirectory.FullPath, "plan.xml"));
         SongEntryViewModel entry = viewModel.Entries[0];
         string originalArtist = entry.Artist;
 
@@ -147,9 +139,9 @@ public sealed class MainWindowViewModelTests {
     [TestMethod]
     public void FormatChangeUpdatesPreviewsAndMarksDirty() {
         MainWindowViewModel viewModel = new();
-        string sourcePath = Path.Combine(_tempDirectory, "A - B (Live).mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "A - B (Live).mp3");
         viewModel.AddFiles(new[] { sourcePath });
-        viewModel.SavePlan(Path.Combine(_tempDirectory, "plan.xml"));
+        viewModel.SavePlan(Path.Combine(_tempDirectory.FullPath, "plan.xml"));
 
         viewModel.SelectedFormat = RenameFormat.TitleFirst;
 
@@ -163,9 +155,9 @@ public sealed class MainWindowViewModelTests {
     [TestMethod]
     public void SettingSameFormatDoesNotDirty() {
         MainWindowViewModel viewModel = new();
-        string sourcePath = Path.Combine(_tempDirectory, "A.mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "A.mp3");
         viewModel.AddFiles(new[] { sourcePath });
-        viewModel.SavePlan(Path.Combine(_tempDirectory, "plan.xml"));
+        viewModel.SavePlan(Path.Combine(_tempDirectory.FullPath, "plan.xml"));
 
         viewModel.SelectedFormat = RenameFormat.ArtistFirst;
 
@@ -182,9 +174,9 @@ public sealed class MainWindowViewModelTests {
     [TestMethod]
     public void NewPlanClearsDocument() {
         MainWindowViewModel viewModel = new();
-        string sourcePath = Path.Combine(_tempDirectory, "A.mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "A.mp3");
         viewModel.AddFiles(new[] { sourcePath });
-        viewModel.SavePlan(Path.Combine(_tempDirectory, "plan.xml"));
+        viewModel.SavePlan(Path.Combine(_tempDirectory.FullPath, "plan.xml"));
 
         viewModel.NewPlan();
 
@@ -200,9 +192,9 @@ public sealed class MainWindowViewModelTests {
     [TestMethod]
     public void ClosePlanClearsDocument() {
         MainWindowViewModel viewModel = new();
-        string sourcePath = Path.Combine(_tempDirectory, "A.mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "A.mp3");
         viewModel.AddFiles(new[] { sourcePath });
-        viewModel.SavePlan(Path.Combine(_tempDirectory, "plan.xml"));
+        viewModel.SavePlan(Path.Combine(_tempDirectory.FullPath, "plan.xml"));
 
         viewModel.ClosePlan();
 
@@ -217,17 +209,17 @@ public sealed class MainWindowViewModelTests {
     /// </summary>
     [TestMethod]
     public void LoadPlanRestoresDocument() {
-        string planPath = Path.Combine(_tempDirectory, "plan.xml");
+        string planPath = Path.Combine(_tempDirectory.FullPath, "plan.xml");
         SongPlan plan = new() {
             Format = RenameFormat.TitleFirst,
             Items = new List<PlanItem> {
                 new PlanItem {
-                    Path = Path.Combine(_tempDirectory, "A - B.mp3"),
+                    Path = Path.Combine(_tempDirectory.FullPath, "A - B.mp3"),
                     Artist = "A",
                     Title = "B",
                 },
                 new PlanItem {
-                    Path = Path.Combine(_tempDirectory, "C.mp3"),
+                    Path = Path.Combine(_tempDirectory.FullPath, "C.mp3"),
                     Title = "C",
                     Comment = "Live",
                 },
@@ -253,10 +245,10 @@ public sealed class MainWindowViewModelTests {
     [TestMethod]
     public void SavePlanWritesDocumentAndClearsDirty() {
         MainWindowViewModel viewModel = new();
-        string sourcePath = Path.Combine(_tempDirectory, "A - B (Live).mp3");
+        string sourcePath = Path.Combine(_tempDirectory.FullPath, "A - B (Live).mp3");
         viewModel.AddFiles(new[] { sourcePath });
         viewModel.SelectedFormat = RenameFormat.TitleFirst;
-        string planPath = Path.Combine(_tempDirectory, "saved.xml");
+        string planPath = Path.Combine(_tempDirectory.FullPath, "saved.xml");
 
         viewModel.SavePlan(planPath);
 
@@ -306,8 +298,8 @@ public sealed class MainWindowViewModelTests {
     /// <param name="fileName">The relative file name, which may include a subdirectory.</param>
     /// <returns>The full path of the created file.</returns>
     private string CreateFile(string fileName) {
-        string path = Path.Combine(_tempDirectory, fileName);
-        string directory = Path.GetDirectoryName(path) ?? _tempDirectory;
+        string path = Path.Combine(_tempDirectory.FullPath, fileName);
+        string directory = Path.GetDirectoryName(path) ?? _tempDirectory.FullPath;
 
         Directory.CreateDirectory(directory);
         File.WriteAllText(path, string.Empty);
diff --git a/SongTidy.Tests/SongEntryViewModelTests.cs b/SongTidy.Tests/ViewModels/SongEntryViewModelTests.cs
similarity index 99%
rename from SongTidy.Tests/SongEntryViewModelTests.cs
rename to SongTidy.Tests/ViewModels/SongEntryViewModelTests.cs
index 9926558..79fe690 100644
--- a/SongTidy.Tests/SongEntryViewModelTests.cs
+++ b/SongTidy.Tests/ViewModels/SongEntryViewModelTests.cs
@@ -3,7 +3,7 @@ using System.IO;
 using SongTidy.Models;
 using SongTidy.ViewModels;
 
-namespace SongTidy.Tests;
+namespace SongTidy.Tests.ViewModels;
 
 /// <summary>
 /// Contains tests for <see cref="SongEntryViewModel"/>.