diff --git a/.coverage b/.coverage
index 1ff4a45..618aa76 100644
Binary files a/.coverage and b/.coverage differ
diff --git a/.cursorrules b/.cursorrules
index 61f2508..76ff318 100644
--- a/.cursorrules
+++ b/.cursorrules
@@ -105,6 +105,7 @@
         "styling": "Not applicable",
         "testing_framework": "pytest",
         "build_tool": "setuptools",
+        "use_venv": ".venv",
         
         "deployment": {
             "environment": "Local machine",
diff --git a/tests/test_config.py b/tests/test_config.py
index 6d3e6ed..988e836 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -38,6 +38,13 @@ def test_can_access_miniapp_denied(monkeypatch):
     assert config.can_access_miniapp("") is False
 
 
+def test_settings_from_env_parse_admin_phones_adds_normalized(monkeypatch):
+    """Settings.from_env() parses ADMIN_PHONES and adds normalized phone to admin_phones."""
+    monkeypatch.setenv("ADMIN_PHONES", "+7 900 123-45-67")
+    settings = config.Settings.from_env()
+    assert settings.admin_phones == {"79001234567"}
+
+
 def test_normalize_phone():
     """Phone is normalized to digits only."""
     assert config.normalize_phone("+7 900 123-45-67") == "79001234567"
diff --git a/tests/test_handlers_common.py b/tests/test_handlers_common.py
new file mode 100644
index 0000000..d1fa803
--- /dev/null
+++ b/tests/test_handlers_common.py
@@ -0,0 +1,52 @@
+"""Tests for duty_teller.handlers.common (is_admin_async)."""
+
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from duty_teller.handlers.common import is_admin_async
+
+
+@pytest.mark.asyncio
+async def test_is_admin_async_true_when_repository_returns_true():
+    """is_admin_async returns True when is_admin_for_telegram_user returns True."""
+    mock_session = MagicMock()
+    mock_scope = MagicMock()
+    mock_scope.return_value.__enter__.return_value = mock_session
+    mock_scope.return_value.__exit__.return_value = None
+
+    with patch(
+        "duty_teller.handlers.common.session_scope",
+        mock_scope,
+    ):
+        with patch(
+            "duty_teller.handlers.common.is_admin_for_telegram_user",
+            return_value=True,
+        ) as mock_is_admin:
+            result = await is_admin_async(12345)
+    assert result is True
+    mock_scope.assert_called_once()
+    mock_scope.return_value.__enter__.assert_called_once()
+    mock_is_admin.assert_called_once_with(mock_session, 12345)
+
+
+@pytest.mark.asyncio
+async def test_is_admin_async_false_when_repository_returns_false():
+    """is_admin_async returns False when is_admin_for_telegram_user returns False."""
+    mock_session = MagicMock()
+    mock_scope = MagicMock()
+    mock_scope.return_value.__enter__.return_value = mock_session
+    mock_scope.return_value.__exit__.return_value = None
+
+    with patch(
+        "duty_teller.handlers.common.session_scope",
+        mock_scope,
+    ):
+        with patch(
+            "duty_teller.handlers.common.is_admin_for_telegram_user",
+            return_value=False,
+        ) as mock_is_admin:
+            result = await is_admin_async(99999)
+    assert result is False
+    mock_scope.assert_called_once()
+    mock_is_admin.assert_called_once_with(mock_session, 99999)
diff --git a/tests/test_handlers_errors.py b/tests/test_handlers_errors.py
index f4712b8..ca2eb05 100644
--- a/tests/test_handlers_errors.py
+++ b/tests/test_handlers_errors.py
@@ -52,3 +52,26 @@ async def test_error_handler_update_none_does_not_crash():
     context = MagicMock()
     context.error = Exception("test")
     await error_handler(None, context)
+
+
+@pytest.mark.asyncio
+async def test_error_handler_reply_text_raises_does_not_propagate():
+    """error_handler: when reply_text raises, exception is caught and logged; does not propagate."""
+    class FakeUpdate:
+        pass
+
+    update = FakeUpdate()
+    update.effective_message = MagicMock()
+    update.effective_message.reply_text = AsyncMock(
+        side_effect=Exception("reply failed")
+    )
+    update.effective_user = MagicMock()
+    context = MagicMock()
+    context.error = Exception("test error")
+
+    with patch("duty_teller.handlers.errors.Update", FakeUpdate):
+        with patch("duty_teller.handlers.errors.get_lang", return_value="en"):
+            with patch("duty_teller.handlers.errors.t", return_value="An error occurred."):
+                await error_handler(update, context)
+    # Handler must not raise; reply_text was attempted
+    update.effective_message.reply_text.assert_called_once()
diff --git a/tests/test_personal_calendar_ics.py b/tests/test_personal_calendar_ics.py
index 0511eb4..a2089f2 100644
--- a/tests/test_personal_calendar_ics.py
+++ b/tests/test_personal_calendar_ics.py
@@ -58,3 +58,19 @@ def test_build_personal_ics_event_types():
     summaries = [str(ev.get("summary")) for ev in events]
     assert "Unavailable" in summaries
     assert "Vacation" in summaries
+
+
+def test_build_personal_ics_naive_datetime_treated_as_utc():
+    """Duties with start_at/end_at without Z (naive datetime) are treated as UTC."""
+    duties = [
+        _duty(1, "2025-02-20T09:00:00", "2025-02-20T18:00:00", "duty"),
+    ]
+    ics = build_personal_ics(duties)
+    cal = ICalendar.from_ical(ics)
+    assert cal is not None
+    events = [c for c in cal.walk() if c.name == "VEVENT"]
+    assert len(events) == 1
+    ev = events[0]
+    assert ev.get("summary") == "Duty"
+    assert "2025-02-20" in str(ev.get("dtstart").dt)
+    assert "2025-02-20" in str(ev.get("dtend").dt)