diff --git a/tests/test_undo_manager.py b/tests/test_undo_manager.py
index 1fa25fa..3cf56cb 100644
--- a/tests/test_undo_manager.py
+++ b/tests/test_undo_manager.py
@@ -1,13 +1,30 @@
+import pytest
+
+from logic.scheduler import Task
+from logic.storage import sqlite_storage as storage
 from logic.undo_manager import UndoManager
 
 
 class RecordingScheduler:
     def __init__(self):
+        self.tasks = []
         self.deleted = []
+        self.updated = []
+        self.completed = []
+        self.uncompleted = []
 
     def delete_task(self, task_id):
         self.deleted.append(task_id)
 
+    def update_task(self, task):
+        self.updated.append(task)
+
+    def complete_task(self, task_id):
+        self.completed.append(task_id)
+
+    def uncomplete_task(self, task_id):
+        self.uncompleted.append(task_id)
+
 
 class FailingScheduler:
     def delete_task(self, _task_id):
@@ -24,6 +41,64 @@ def test_successful_undo_consumes_action():
     assert not manager.can_undo()
 
 
+def test_undo_delete_restores_original_task(monkeypatch):
+    scheduler = RecordingScheduler()
+    manager = UndoManager(scheduler)
+    task = Task(id="task-1", date="2026-08-28", time="09:00", text="Restore me")
+    restored = []
+    monkeypatch.setattr(storage, "create_entry", restored.append)
+    manager.record_delete(task)
+
+    assert manager.undo() == "Undid delete"
+    assert restored == [task]
+    assert scheduler.tasks == [task]
+
+
+def test_undo_edit_restores_snapshot():
+    scheduler = RecordingScheduler()
+    manager = UndoManager(scheduler)
+    snapshot = Task(id="task-1", date="2026-08-28", time="09:00", text="Before")
+    manager.record_edit(snapshot)
+
+    assert manager.undo() == "Undid edit"
+    assert scheduler.updated == [snapshot]
+
+
+@pytest.mark.parametrize(
+    ("record_method", "expected_result", "recorded_attribute"),
+    [
+        ("record_complete", "Undid complete", "uncompleted"),
+        ("record_uncomplete", "Undid uncomplete", "completed"),
+    ],
+)
+def test_undo_completion_state(record_method, expected_result, recorded_attribute):
+    scheduler = RecordingScheduler()
+    manager = UndoManager(scheduler)
+    getattr(manager, record_method)("task-1")
+
+    assert manager.undo() == expected_result
+    assert getattr(scheduler, recorded_attribute) == ["task-1"]
+
+
+def test_undo_empty_history_returns_none():
+    assert UndoManager(RecordingScheduler()).undo() is None
+
+
+def test_history_limit_drops_oldest_actions():
+    scheduler = RecordingScheduler()
+    manager = UndoManager(scheduler)
+    for index in range(manager.MAX_HISTORY + 1):
+        manager.record_add(f"task-{index}")
+
+    while manager.can_undo():
+        manager.undo()
+
+    assert len(scheduler.deleted) == manager.MAX_HISTORY
+    assert scheduler.deleted[0] == "task-50"
+    assert scheduler.deleted[-1] == "task-1"
+    assert "task-0" not in scheduler.deleted
+
+
 def test_failed_undo_is_logged_and_remains_available(caplog):
     manager = UndoManager(FailingScheduler())
     manager.record_add("task-1")