Datensicherheit: Backup, Verschlüsselung, App-Sperre (Kapitel 13.3)

Automatisches rollierendes Backup der Datenbank beim Start mit
Wiederherstellung über die Einstellungen, versionierte Schema-Migration,
optionale Passwort-Verschlüsselung der LiteDB-Datei und eine App-Sperre
nach Inaktivität mit eigenem Passwort.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

LehrerApp.Tests/AppLockServiceTests.cs

@@ -0,0 +1,74 @@
+using LehrerApp.Core.Services;
+using Xunit;
+
+namespace LehrerApp.Tests;
+
+public sealed class AppLockServiceTests
+{
+    [Fact]
+    public void NeueKonfiguration_IstStandardmaessigDeaktiviert()
+    {
+        using var temp = new TempAppData();
+        var service = new AppLockService(temp.Path);
+
+        Assert.False(service.IsEnabled);
+        Assert.False(service.HasPassword);
+    }
+
+    [Fact]
+    public void SetPassword_VerifyPassword_KorrektesPasswortWirdAkzeptiert()
+    {
+        using var temp = new TempAppData();
+        var service = new AppLockService(temp.Path);
+
+        service.SetPassword("geheim123");
+
+        Assert.True(service.HasPassword);
+        Assert.True(service.VerifyPassword("geheim123"));
+        Assert.False(service.VerifyPassword("falsch"));
+    }
+
+    [Fact]
+    public void Configure_WirdUeberNeueInstanzHinwegPersistiert()
+    {
+        using var temp = new TempAppData();
+        var first = new AppLockService(temp.Path);
+        first.SetPassword("geheim123");
+        first.Configure(enabled: true, timeoutMinutes: 15);
+
+        var second = new AppLockService(temp.Path);
+
+        Assert.True(second.IsEnabled);
+        Assert.Equal(15, second.TimeoutMinutes);
+        Assert.True(second.VerifyPassword("geheim123"));
+    }
+
+    [Fact]
+    public void VerifyPassword_OhneGesetztesPasswort_GibtFalseZurueck()
+    {
+        using var temp = new TempAppData();
+        var service = new AppLockService(temp.Path);
+
+        Assert.False(service.VerifyPassword("irgendwas"));
+    }
+
+    [Fact]
+    public void Configure_TimeoutUnterEinerMinute_WirdAufEineMinuteBegrenzt()
+    {
+        using var temp = new TempAppData();
+        var service = new AppLockService(temp.Path);
+
+        service.Configure(enabled: true, timeoutMinutes: 0);
+
+        Assert.Equal(1, service.TimeoutMinutes);
+    }
+
+    private sealed class TempAppData : IDisposable
+    {
+        public string Path { get; } = System.IO.Path.Combine(
+            System.IO.Path.GetTempPath(), $"lehrerapp-applock-tests-{Guid.NewGuid():N}");
+
+        public TempAppData() => Directory.CreateDirectory(Path);
+        public void Dispose() { if (Directory.Exists(Path)) Directory.Delete(Path, recursive: true); }
+    }
+}

LehrerApp.Tests/BackupServiceTests.cs

@@ -0,0 +1,103 @@
+using LehrerApp.Core.Services;
+using Xunit;
+
+namespace LehrerApp.Tests;
+
+public sealed class BackupServiceTests
+{
+    [Fact]
+    public void CreateBackup_OhneVorhandeneDatenbank_GibtNullZurueck()
+    {
+        using var temp = new TempAppData();
+        var service = new BackupService(temp.Path);
+
+        var result = service.CreateBackup(Path.Combine(temp.Path, "fehlt.db"));
+
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void CreateBackup_KopiertDieDatenbankdatei()
+    {
+        using var temp = new TempAppData();
+        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
+        File.WriteAllText(dbPath, "Testinhalt");
+        var service = new BackupService(temp.Path);
+
+        var backupPath = service.CreateBackup(dbPath);
+
+        Assert.NotNull(backupPath);
+        Assert.True(File.Exists(backupPath));
+        Assert.Equal("Testinhalt", File.ReadAllText(backupPath!));
+    }
+
+    [Fact]
+    public void ListBackups_SortiertNeuesteZuerst()
+    {
+        using var temp = new TempAppData();
+        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
+        File.WriteAllText(dbPath, "v1");
+        var service = new BackupService(temp.Path);
+
+        var first = service.CreateBackup(dbPath)!;
+        File.SetLastWriteTime(first, DateTime.Now.AddMinutes(-5));
+        File.WriteAllText(dbPath, "v2");
+        var second = service.CreateBackup(dbPath)!;
+
+        var backups = service.ListBackups();
+
+        Assert.Equal(2, backups.Count);
+        Assert.Equal(second, backups[0].Path);
+    }
+
+    [Fact]
+    public void CreateBackup_BehaeltNurDieLetztenNBackups()
+    {
+        using var temp = new TempAppData();
+        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
+        var service = new BackupService(temp.Path);
+
+        for (var i = 0; i < 5; i++)
+        {
+            File.WriteAllText(dbPath, $"v{i}");
+            var backup = service.CreateBackup(dbPath, keepCount: 3)!;
+            File.SetLastWriteTime(backup, DateTime.Now.AddMinutes(-5 + i));
+        }
+
+        Assert.Equal(3, service.ListBackups().Count);
+    }
+
+    [Fact]
+    public void RestoreBackup_KopiertBackupUeberDieZieldatei()
+    {
+        using var temp = new TempAppData();
+        var dbPath = Path.Combine(temp.Path, "lehrerapp.db");
+        File.WriteAllText(dbPath, "alt");
+        var service = new BackupService(temp.Path);
+        var backupPath = service.CreateBackup(dbPath)!;
+        File.WriteAllText(dbPath, "neu-kaputt");
+
+        service.RestoreBackup(backupPath, dbPath);
+
+        Assert.Equal("alt", File.ReadAllText(dbPath));
+    }
+
+    [Fact]
+    public void RestoreBackup_OhneVorhandenesBackup_WirftException()
+    {
+        using var temp = new TempAppData();
+        var service = new BackupService(temp.Path);
+
+        Assert.Throws<FileNotFoundException>(() =>
+            service.RestoreBackup(Path.Combine(temp.Path, "backups", "fehlt.db"), Path.Combine(temp.Path, "lehrerapp.db")));
+    }
+
+    private sealed class TempAppData : IDisposable
+    {
+        public string Path { get; } = System.IO.Path.Combine(
+            System.IO.Path.GetTempPath(), $"lehrerapp-backup-tests-{Guid.NewGuid():N}");
+
+        public TempAppData() => Directory.CreateDirectory(Path);
+        public void Dispose() { if (Directory.Exists(Path)) Directory.Delete(Path, recursive: true); }
+    }
+}