refactored broad range of the application, split files, modularized calendar and file views, centralized bottom sheets and clipboard handling, and implemented unit test coverage

test/utils/file_clipboard_test.dart

@@ -0,0 +1,97 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:marianum_mobile/api/marianumcloud/webdav/queries/list_files/cacheable_file.dart';
+import 'package:marianum_mobile/utils/file_clipboard.dart';
+
+CacheableFile _file(String name) =>
+    CacheableFile(path: '/$name', isDirectory: false, name: name);
+
+void main() {
+  // FileClipboard is a singleton — clear between tests so state doesn't leak.
+  setUp(FileClipboard.instance.clear);
+
+  group('FileClipboard.cut', () {
+    test('switches to cut state and notifies listeners', () {
+      final cb = FileClipboard.instance;
+      var notifyCount = 0;
+      void listener() => notifyCount++;
+      cb.addListener(listener);
+      addTearDown(() => cb.removeListener(listener));
+
+      cb.cut([_file('a.txt')]);
+
+      expect(cb.operation, FileClipboardOperation.cut);
+      expect(cb.files.map((f) => f.name), ['a.txt']);
+      expect(cb.isEmpty, isFalse);
+      expect(notifyCount, 1);
+    });
+
+    test('empty input is a no-op', () {
+      final cb = FileClipboard.instance;
+      var notifyCount = 0;
+      void listener() => notifyCount++;
+      cb.addListener(listener);
+      addTearDown(() => cb.removeListener(listener));
+
+      cb.cut(const []);
+
+      expect(cb.operation, isNull);
+      expect(cb.isEmpty, isTrue);
+      expect(notifyCount, 0, reason: 'no state change → no notifyListeners');
+    });
+
+    test('files getter returns an unmodifiable view', () {
+      final cb = FileClipboard.instance;
+      cb.cut([_file('a.txt')]);
+      expect(() => cb.files.add(_file('b.txt')), throwsUnsupportedError);
+    });
+  });
+
+  group('FileClipboard.copy', () {
+    test('switches to copy state and notifies listeners', () {
+      final cb = FileClipboard.instance;
+      cb.copy([_file('a.txt'), _file('b.txt')]);
+
+      expect(cb.operation, FileClipboardOperation.copy);
+      expect(cb.files, hasLength(2));
+    });
+
+    test('overwrites a previous cut state', () {
+      final cb = FileClipboard.instance;
+      cb.cut([_file('cut.txt')]);
+      cb.copy([_file('copy.txt')]);
+
+      expect(cb.operation, FileClipboardOperation.copy);
+      expect(cb.files.single.name, 'copy.txt');
+    });
+  });
+
+  group('FileClipboard.clear', () {
+    test('resets state and notifies', () {
+      final cb = FileClipboard.instance;
+      cb.copy([_file('a.txt')]);
+      var notifyCount = 0;
+      void listener() => notifyCount++;
+      cb.addListener(listener);
+      addTearDown(() => cb.removeListener(listener));
+
+      cb.clear();
+
+      expect(cb.operation, isNull);
+      expect(cb.isEmpty, isTrue);
+      expect(notifyCount, 1);
+    });
+
+    test('clearing an already-empty clipboard is a no-op', () {
+      final cb = FileClipboard.instance;
+      var notifyCount = 0;
+      void listener() => notifyCount++;
+      cb.addListener(listener);
+      addTearDown(() => cb.removeListener(listener));
+
+      cb.clear();
+      cb.clear();
+
+      expect(notifyCount, 0);
+    });
+  });
+}