Add comprehensive test coverage for 8 modules

Increases overall test coverage from 53% to 56% by adding tests for:
- accommodation.py (60% → 100%)
- birthday.py (24% → 100%)
- calendar.py (19% → 100%)
- carnival.py (33% → 100%)
- domains.py (75% → 100%)
- events_yaml.py (50% → 96%)
- fx.py (14% → 21% for tested functions)
- sun.py (55% → 100%)

🤖 Generated with [Claude Code](https://claude.ai/code)

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

tests/test_events_yaml.py

@@ -0,0 +1,49 @@
+"""Tests for events_yaml functionality."""
+
+from datetime import date, datetime, time
+
+from agenda.events_yaml import midnight
+
+
+class TestMidnight:
+    """Test the midnight function."""
+
+    def test_midnight_with_date(self) -> None:
+        """Test converting date to midnight datetime."""
+        test_date = date(2024, 6, 15)
+        result = midnight(test_date)
+        
+        assert isinstance(result, datetime)
+        assert result.date() == test_date
+        assert result.time() == time(0, 0, 0)  # Midnight
+        assert result == datetime(2024, 6, 15, 0, 0, 0)
+
+    def test_midnight_different_dates(self) -> None:
+        """Test midnight function with different dates."""
+        test_cases = [
+            date(2024, 1, 1),    # New Year's Day
+            date(2024, 12, 31),  # New Year's Eve
+            date(2024, 2, 29),   # Leap day
+            date(2024, 7, 4),    # Independence Day
+        ]
+        
+        for test_date in test_cases:
+            result = midnight(test_date)
+            assert result.date() == test_date
+            assert result.time() == time(0, 0, 0)
+            assert result.hour == 0
+            assert result.minute == 0
+            assert result.second == 0
+            assert result.microsecond == 0
+
+    def test_midnight_preserves_year_month_day(self) -> None:
+        """Test that midnight preserves the year, month, and day."""
+        test_date = date(2023, 11, 27)
+        result = midnight(test_date)
+        
+        assert result.year == 2023
+        assert result.month == 11
+        assert result.day == 27
+        assert result.hour == 0
+        assert result.minute == 0
+        assert result.second == 0