Add comprehensive tests for formatter classes, services, and utilities

- Introduced tests for various formatter classes including TextFormatter, DurationFormatter, SizeFormatter, DateFormatter, and more to ensure correct formatting behavior.
- Added tests for service classes such as FileTreeService, MetadataService, and RenameService, covering directory validation, metadata extraction, and file renaming functionalities.
- Implemented utility tests for LanguageCodeExtractor, PatternExtractor, and FrameClassMatcher to validate their extraction and matching capabilities.
- Updated test cases to use datasets for better maintainability and clarity.
- Enhanced error handling tests to ensure robustness against missing or invalid data.

renamer/test/test_metadata_extractor.py

@@ -1,32 +1,82 @@
 import pytest
+import json
 from pathlib import Path
 from renamer.extractors.metadata_extractor import MetadataExtractor
 
 
 class TestMetadataExtractor:
+    """
+    Note: MetadataExtractor requires actual media files with embedded metadata.
+    Since we don't have real media files in the repository, these tests verify
+    the extractor handles missing/empty metadata gracefully.
+
+    Real integration tests with actual media files should be done manually.
+    """
+
+    @pytest.fixture
+    def dataset(self):
+        """Load filename patterns dataset for test data"""
+        dataset_file = Path(__file__).parent / "datasets" / "filenames" / "filename_patterns.json"
+        with open(dataset_file, 'r', encoding='utf-8') as f:
+            return json.load(f)
+
+    @pytest.fixture
+    def test_file(self):
+        """Use the dataset JSON file (has no media metadata)"""
+        return Path(__file__).parent / "datasets" / "filenames" / "filename_patterns.json"
+
     @pytest.fixture
     def extractor(self, test_file):
         return MetadataExtractor(test_file)
 
-    @pytest.fixture
-    def test_file(self):
-        """Use the filenames.txt file for testing"""
-        return Path(__file__).parent / "filenames.txt"
-
     def test_extract_title(self, extractor):
-        """Test extracting title from metadata"""
+        """Test extracting title from metadata - should return None for non-media files"""
         title = extractor.extract_title()
-        # Text files don't have metadata, so should be None
         assert title is None
 
     def test_extract_duration(self, extractor):
-        """Test extracting duration from metadata"""
+        """Test extracting duration from metadata - should return None for non-media files"""
         duration = extractor.extract_duration()
-        # Text files don't have duration
         assert duration is None
 
     def test_extract_artist(self, extractor):
-        """Test extracting artist from metadata"""
+        """Test extracting artist from metadata - should return None for non-media files"""
         artist = extractor.extract_artist()
-        # Text files don't have artist
-        assert artist is None
+        assert artist is None
+
+    def test_extract_meta_type(self, extractor):
+        """Test extracting meta type - should detect file type"""
+        meta_type = extractor.extract_meta_type()
+        # Should return some string describing file type
+        assert isinstance(meta_type, str)
+
+    def test_handles_missing_metadata(self, test_file):
+        """Test that extractor doesn't crash on files without metadata"""
+        extractor = MetadataExtractor(test_file)
+        # Should not raise exceptions
+        assert extractor.extract_title() is None
+        assert extractor.extract_duration() is None
+        assert extractor.extract_artist() is None
+
+    def test_handles_nonexistent_file(self):
+        """Test that extractor handles nonexistent files gracefully"""
+        fake_file = Path("/nonexistent/file.mkv")
+        extractor = MetadataExtractor(fake_file)
+        # Should return None instead of crashing
+        assert extractor.extract_title() is None
+
+    def test_dataset_available(self, dataset):
+        """Verify test dataset is available and valid"""
+        assert 'test_cases' in dataset
+        assert len(dataset['test_cases']) > 0
+        # Verify dataset has expected structure
+        first_case = dataset['test_cases'][0]
+        assert 'filename' in first_case
+        assert 'expected' in first_case
+
+
+# Note: Full integration tests with real media files should include:
+# - Extracting metadata from actual MKV/MP4 files
+# - Testing with files that have metadata tags
+# - Verifying metadata extraction accuracy
+# These tests require actual media files which are not in the repository.