diff --git a/.gitignore b/.gitignore
index ad429e4..1e18cb9 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,4 +2,5 @@
 .vscode
 *.sif
 *.ipynb
-backups
\ No newline at end of file
+backups
+.pytest_cache
\ No newline at end of file
diff --git a/tests/test_backup.py b/tests/test_backup.py
index d21e289..635bed4 100644
--- a/tests/test_backup.py
+++ b/tests/test_backup.py
@@ -1,5 +1,6 @@
 import zipfile
 import datetime
+from unittest.mock import patch
 from utils import backup
 
 
@@ -31,4 +32,183 @@ def test_backup_creates_zip(tmp_path, monkeypatch):
         assert any('file2.txt' in n for n in names)
     
     # Cleanup: remove the backup file after test
-    backup_path.unlink()
\ No newline at end of file
+    backup_path.unlink()
+
+
+def test_backup_with_subdirectories(tmp_path, monkeypatch):
+    # Setup fake web folder with subdirectories
+    web_folder = tmp_path / 'plots'
+    web_folder.mkdir()
+    (web_folder / 'file1.txt').write_text('content1')
+    
+    subdir = web_folder / 'subdir'
+    subdir.mkdir()
+    (subdir / 'file2.txt').write_text('content2')
+    
+    nested_subdir = subdir / 'nested'
+    nested_subdir.mkdir()
+    (nested_subdir / 'file3.txt').write_text('content3')
+    
+    backup_folder = tmp_path / 'backups'
+    backup_folder.mkdir()
+
+    # Patch the module variables
+    monkeypatch.setattr(backup, 'WEB_FOLDER', web_folder)
+    monkeypatch.setattr(backup, 'BACKUP_FOLDER', backup_folder)
+
+    # Call the backup function
+    backup.create_backup()
+    
+    # Check that backup was created with all files
+    today = datetime.date.today().strftime('%Y%m%d')
+    backup_name = f'backup-{today}.zip'
+    backup_path = backup_folder / backup_name
+
+    assert backup_path.exists()
+    with zipfile.ZipFile(backup_path, 'r') as z:
+        names = z.namelist()
+        assert any('file1.txt' in n for n in names)
+        assert any('file2.txt' in n for n in names)
+        assert any('file3.txt' in n for n in names)
+    
+    # Cleanup
+    backup_path.unlink()
+
+
+def test_backup_existing_file(tmp_path, monkeypatch, capsys):
+    # Setup fake web folder
+    web_folder = tmp_path / 'plots'
+    web_folder.mkdir()
+    (web_folder / 'file1.txt').write_text('abc')
+    
+    backup_folder = tmp_path / 'backups'
+    backup_folder.mkdir()
+
+    # Create existing backup file
+    today = datetime.date.today().strftime('%Y%m%d')
+    backup_name = f'backup-{today}.zip'
+    backup_path = backup_folder / backup_name
+    backup_path.write_text('existing backup')
+
+    # Patch the module variables
+    monkeypatch.setattr(backup, 'WEB_FOLDER', web_folder)
+    monkeypatch.setattr(backup, 'BACKUP_FOLDER', backup_folder)
+
+    # Call the backup function
+    backup.create_backup()
+    
+    # Check that message about existing backup was printed
+    captured = capsys.readouterr()
+    assert f"Backup already exists: {backup_path}" in captured.out
+    
+    # Cleanup
+    backup_path.unlink()
+
+
+def test_backup_empty_folder(tmp_path, monkeypatch):
+    # Setup empty web folder
+    web_folder = tmp_path / 'plots'
+    web_folder.mkdir()
+    
+    backup_folder = tmp_path / 'backups'
+    backup_folder.mkdir()
+
+    # Patch the module variables
+    monkeypatch.setattr(backup, 'WEB_FOLDER', web_folder)
+    monkeypatch.setattr(backup, 'BACKUP_FOLDER', backup_folder)
+
+    # Call the backup function
+    backup.create_backup()
+    
+    # Check that backup was created (empty)
+    today = datetime.date.today().strftime('%Y%m%d')
+    backup_name = f'backup-{today}.zip'
+    backup_path = backup_folder / backup_name
+
+    assert backup_path.exists()
+    with zipfile.ZipFile(backup_path, 'r') as z:
+        assert len(z.namelist()) == 0
+    
+    # Cleanup
+    backup_path.unlink()
+
+
+def test_backup_nonexistent_web_folder(tmp_path, monkeypatch):
+    # Setup nonexistent web folder
+    web_folder = tmp_path / 'nonexistent_plots'
+    backup_folder = tmp_path / 'backups'
+    backup_folder.mkdir()
+
+    # Patch the module variables
+    monkeypatch.setattr(backup, 'WEB_FOLDER', web_folder)
+    monkeypatch.setattr(backup, 'BACKUP_FOLDER', backup_folder)
+
+    # Call the backup function
+    backup.create_backup()
+    
+    # Check that backup was created (empty since source doesn't exist)
+    today = datetime.date.today().strftime('%Y%m%d')
+    backup_name = f'backup-{today}.zip'
+    backup_path = backup_folder / backup_name
+
+    assert backup_path.exists()
+    with zipfile.ZipFile(backup_path, 'r') as z:
+        assert len(z.namelist()) == 0
+    
+    # Cleanup
+    backup_path.unlink()
+
+
+@patch('datetime.date')
+def test_backup_with_custom_date(mock_date, tmp_path, monkeypatch):
+    # Mock date to return a specific date
+    mock_date.today.return_value.strftime.return_value = "20230908"
+    
+    # Setup fake web folder
+    web_folder = tmp_path / 'plots'
+    web_folder.mkdir()
+    (web_folder / 'file1.txt').write_text('test')
+    
+    backup_folder = tmp_path / 'backups'
+    backup_folder.mkdir()
+
+    # Patch the module variables
+    monkeypatch.setattr(backup, 'WEB_FOLDER', web_folder)
+    monkeypatch.setattr(backup, 'BACKUP_FOLDER', backup_folder)
+
+    # Call the backup function
+    backup.create_backup()
+    
+    # Check that backup was created with custom date
+    backup_path = backup_folder / "backup-20230908.zip"
+    assert backup_path.exists()
+    
+    # Cleanup
+    backup_path.unlink()
+
+
+def test_backup_folder_creation(tmp_path, monkeypatch):
+    # Setup fake web folder
+    web_folder = tmp_path / 'plots'
+    web_folder.mkdir()
+    (web_folder / 'file1.txt').write_text('test')
+    
+    # Don't create backup folder - let function create it
+    backup_folder = tmp_path / 'new_backups'
+
+    # Patch the module variables
+    monkeypatch.setattr(backup, 'WEB_FOLDER', web_folder)
+    monkeypatch.setattr(backup, 'BACKUP_FOLDER', backup_folder)
+
+    # Call the backup function
+    backup.create_backup()
+    
+    # Check that backup folder was created
+    assert backup_folder.exists()
+    assert backup_folder.is_dir()
+    
+    # Check that backup file was created
+    today = datetime.date.today().strftime('%Y%m%d')
+    backup_name = f'backup-{today}.zip'
+    backup_path = backup_folder / backup_name
+    assert backup_path.exists()
\ No newline at end of file
diff --git a/tests/test_build_container.py b/tests/test_build_container.py
deleted file mode 100644
index e69de29..0000000
diff --git a/tests/test_config.py b/tests/test_config.py
index 2343c20..ed2d134 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -1,3 +1,7 @@
+from pathlib import Path
+import tempfile
+import pytest
+import yaml
 from utils import config
 
 
@@ -25,3 +29,169 @@ def test_metadata_config_defaults():
     mc = config.MetadataConfig()
     assert mc.cache_enabled is True
     assert mc.inherit_from_parent is True
+    assert mc.supported_formats == ['.yaml', '.yml', '.json']
+
+
+def test_metadata_config_custom():
+    mc = config.MetadataConfig(
+        cache_enabled=False,
+        inherit_from_parent=False,
+        supported_formats=['.yaml']
+    )
+    assert mc.cache_enabled is False
+    assert mc.inherit_from_parent is False
+    assert mc.supported_formats == ['.yaml']
+
+
+def test_gallery_item():
+    item = config.GalleryItem(name="test", path=Path("/test/path"))
+    assert item.name == "test"
+    assert item.path == Path("/test/path")
+
+
+def test_config_creation():
+    paths = config.PathConfig(work_dir="/work", web_folder="/web")
+    gallery = config.GalleryConfig(
+        plot_root="plots", png_dpi=300, backup_folder="backups")
+    ui = config.UIConfig(max_recent_plots=5, search_debounce_ms=100)
+    metadata = config.MetadataConfig()
+
+    cfg = config.Config(
+        paths=paths,
+        gallery=gallery,
+        ui=ui,
+        metadata=metadata
+    )
+
+    assert cfg.paths == paths
+    assert cfg.gallery == gallery
+    assert cfg.ui == ui
+    assert cfg.metadata == metadata
+    assert cfg.sources == []
+
+
+def test_config_backward_compatibility_properties():
+    paths = config.PathConfig(work_dir="/work", web_folder="/web")
+    gallery = config.GalleryConfig(
+        plot_root="plots", png_dpi=300, backup_folder="backups")
+    ui = config.UIConfig(max_recent_plots=5, search_debounce_ms=100)
+    metadata = config.MetadataConfig()
+
+    cfg = config.Config(
+        paths=paths,
+        gallery=gallery,
+        ui=ui,
+        metadata=metadata
+    )
+
+    assert cfg.web_folder == "/web"
+    assert cfg.png_dpi == 300
+    assert cfg.plot_root == "plots"
+    assert cfg.backup_folder == "backups"
+
+
+def test_config_from_yaml(tmp_path):
+    yaml_content = {
+        'paths': {
+            'work_dir': '/test/work',
+            'web_folder': '/test/web'
+        },
+        'gallery': {
+            'plot_root': 'test_plots',
+            'png_dpi': 200,
+            'backup_folder': 'test_backups'
+        },
+        'ui': {
+            'max_recent_plots': 15,
+            'search_debounce_ms': 300
+        },
+        'metadata': {
+            'cache_enabled': False,
+            'inherit_from_parent': False
+        },
+        'sources': [
+            {'name': 'source1', 'path': '/path1'},
+            {'name': 'source2', 'path': '/path2'}
+        ]
+    }
+
+    yaml_file = tmp_path / 'test_config.yaml'
+    with yaml_file.open('w') as f:
+        yaml.dump(yaml_content, f)
+
+    cfg = config.Config.from_yaml(str(yaml_file))
+
+    assert cfg.paths.work_dir == '/test/work'
+    assert cfg.paths.web_folder == '/test/web'
+    assert cfg.gallery.plot_root == 'test_plots'
+    assert cfg.gallery.png_dpi == 200
+    assert cfg.ui.max_recent_plots == 15
+    assert cfg.metadata.cache_enabled is False
+    assert len(cfg.sources) == 2
+    assert cfg.sources[0].name == 'source1'
+    assert cfg.sources[0].path == Path('/path1')
+
+
+def test_config_from_yaml_missing_file():
+    with pytest.raises(FileNotFoundError):
+        config.Config.from_yaml('/nonexistent/file.yaml')
+
+
+def test_config_from_yaml_malformed():
+    with tempfile.NamedTemporaryFile(mode='w', suffix='.yaml',
+                                     delete=False) as f:
+        f.write('invalid: yaml: content: [')
+        f.flush()
+
+        with pytest.raises(yaml.YAMLError):
+            config.Config.from_yaml(f.name)
+
+
+def test_config_to_yaml(tmp_path):
+    paths = config.PathConfig(work_dir="/work", web_folder="/web")
+    gallery = config.GalleryConfig(
+        plot_root="plots", png_dpi=300, backup_folder="backups")
+    ui = config.UIConfig(max_recent_plots=5, search_debounce_ms=100)
+    metadata = config.MetadataConfig()
+    sources = [config.GalleryItem(name="test", path=Path("/test"))]
+
+    cfg = config.Config(
+        paths=paths,
+        gallery=gallery,
+        ui=ui,
+        metadata=metadata,
+        sources=sources
+    )
+
+    yaml_file = tmp_path / 'output_config.yaml'
+    cfg.to_yaml(str(yaml_file))
+
+    assert yaml_file.exists()
+
+    # Load back and verify
+    with yaml_file.open('r') as f:
+        loaded_data = yaml.safe_load(f)
+
+    assert loaded_data['paths']['work_dir'] == "/work"
+    assert loaded_data['gallery']['png_dpi'] == 300
+    assert len(loaded_data['sources']) == 1
+
+
+def test_config_from_yaml_partial_data(tmp_path):
+    # Test with minimal YAML data
+    yaml_content = {
+        'paths': {'work_dir': '/min', 'web_folder': '/min_web'},
+        'gallery': {'plot_root': 'min_plots', 'png_dpi': 100,
+                    'backup_folder': 'min_backup'},
+        'ui': {'max_recent_plots': 3, 'search_debounce_ms': 50}
+    }
+
+    yaml_file = tmp_path / 'minimal_config.yaml'
+    with yaml_file.open('w') as f:
+        yaml.dump(yaml_content, f)
+
+    cfg = config.Config.from_yaml(str(yaml_file))
+
+    # Should use defaults for metadata and empty sources
+    assert cfg.metadata.cache_enabled is True  # default
+    assert cfg.sources == []  # default empty list
diff --git a/tests/test_container.py b/tests/test_container.py
index 8aacee4..106980a 100644
--- a/tests/test_container.py
+++ b/tests/test_container.py
@@ -17,8 +17,8 @@ def test_python_version():
 def test_required_modules():
     """Test that required Python modules are installed."""
     try:
-        import jinja2  # type: ignore
-        import yaml  # type: ignore
+        import jinja2  # noqa: F401
+        import yaml  # noqa: F401
     except ImportError as e:
         pytest.fail(f"Required module not found: {e}")
 
diff --git a/tests/test_generate_gallery.py b/tests/test_generate_gallery.py
new file mode 100644
index 0000000..dade440
--- /dev/null
+++ b/tests/test_generate_gallery.py
@@ -0,0 +1,279 @@
+from pathlib import Path
+from unittest.mock import patch, MagicMock
+from generate_gallery import (
+    convert_pdf_to_png,
+    needs_update,
+    build_gallery,
+    calculate_directory_stats,
+    format_file_size,
+    datetime_from_timestamp,
+    strftime_filter
+)
+from datetime import datetime
+
+
+def test_format_file_size():
+    assert format_file_size(0) == "0 B"
+    assert format_file_size(1) == "1.0 B"
+    assert format_file_size(1024) == "1.0 KB"
+    assert format_file_size(1048576) == "1.0 MB"
+    assert format_file_size(1073741824) == "1.0 GB"
+    assert format_file_size(1099511627776) == "1.0 TB"
+
+
+def test_format_file_size_edge_cases():
+    assert format_file_size(1023) == "1023.0 B"
+    assert format_file_size(1536) == "1.5 KB"
+    assert format_file_size(2621440) == "2.5 MB"
+
+
+def test_needs_update_missing_target(tmp_path):
+    source = tmp_path / "source.txt"
+    target = tmp_path / "target.txt"
+    source.write_text("test content")
+
+    assert needs_update(source, target) is True
+
+
+def test_needs_update_target_newer(tmp_path):
+    source = tmp_path / "source.txt"
+    target = tmp_path / "target.txt"
+
+    source.write_text("test")
+    target.write_text("test")
+
+    # Make target newer by modifying its timestamp
+    import time
+    time.sleep(0.1)
+    target.touch()
+
+    assert needs_update(source, target) is False
+
+
+def test_needs_update_source_newer(tmp_path):
+    source = tmp_path / "source.txt"
+    target = tmp_path / "target.txt"
+
+    target.write_text("test")
+    import time
+    time.sleep(0.1)
+    source.write_text("test")
+
+    assert needs_update(source, target) is True
+
+
+@patch('subprocess.run')
+def test_convert_pdf_to_png_success(mock_run, tmp_path):
+    pdf_path = tmp_path / "test.pdf"
+    png_path = tmp_path / "test.png"
+    pdf_path.write_text("fake pdf")
+
+    mock_run.return_value = MagicMock(returncode=0)
+
+    convert_pdf_to_png(pdf_path)
+
+    mock_run.assert_called_once()
+    call_args = mock_run.call_args[0][0]
+    assert call_args[0] == "convert"
+    assert str(pdf_path) in call_args
+    assert str(png_path) in call_args
+
+
+@patch('subprocess.run')
+def test_convert_pdf_to_png_already_exists_newer(mock_run, tmp_path):
+    pdf_path = tmp_path / "test.pdf"
+    png_path = tmp_path / "test.png"
+
+    pdf_path.write_text("fake pdf")
+    png_path.write_text("fake png")
+
+    # Make PNG much newer than PDF
+    import time
+    time.sleep(0.1)
+    png_path.touch()
+
+    convert_pdf_to_png(pdf_path)
+
+    # Should not call subprocess since PNG is newer
+    mock_run.assert_not_called()
+
+
+@patch('subprocess.run')
+def test_convert_pdf_to_png_pdf_newer(mock_run, tmp_path):
+    pdf_path = tmp_path / "test.pdf"
+    png_path = tmp_path / "test.png"
+
+    png_path.write_text("fake png")
+    import time
+    time.sleep(0.1)
+    pdf_path.write_text("fake pdf")
+
+    mock_run.return_value = MagicMock(returncode=0)
+
+    convert_pdf_to_png(pdf_path)
+
+    # Should call subprocess since PDF is newer
+    mock_run.assert_called_once()
+
+
+def test_calculate_directory_stats_empty(tmp_path):
+    stats = calculate_directory_stats(tmp_path)
+
+    assert stats["file_count"] == 0
+    assert stats["folder_count"] == 0
+    assert stats["total_size"] == 0
+    assert stats["pdf_size"] == 0
+    assert stats["png_size"] == 0
+
+
+def test_calculate_directory_stats_with_files(tmp_path):
+    # Create test files
+    (tmp_path / "test.pdf").write_text("pdf content")
+    (tmp_path / "test.png").write_text("png content")
+    (tmp_path / "test.txt").write_text("txt content")
+
+    # Create subdirectory
+    subdir = tmp_path / "subdir"
+    subdir.mkdir()
+    (subdir / "nested.pdf").write_text("nested pdf")
+
+    stats = calculate_directory_stats(tmp_path)
+
+    assert stats["file_count"] == 4
+    assert stats["folder_count"] == 1
+    assert stats["total_size"] > 0
+    assert stats["pdf_size"] > 0
+    assert stats["png_size"] > 0
+
+
+def test_calculate_directory_stats_nonexistent():
+    nonexistent = Path("/nonexistent/path")
+    stats = calculate_directory_stats(nonexistent)
+
+    assert stats["file_count"] == 0
+    assert stats["folder_count"] == 0
+    assert stats["total_size"] == 0
+
+
+def test_datetime_from_timestamp():
+    timestamp = 1630000000  # Some Unix timestamp
+    dt = datetime_from_timestamp(timestamp)
+
+    assert isinstance(dt, datetime)
+    assert dt.timestamp() == timestamp
+
+
+def test_strftime_filter():
+    dt = datetime(2023, 9, 8, 14, 30, 0)
+    formatted = strftime_filter(dt, "%Y-%m-%d %H:%M")
+
+    assert formatted == "2023-09-08 14:30"
+
+
+@patch('generate_gallery.template')
+@patch('generate_gallery.save_metadata_cache')
+@patch('generate_gallery.resolve_metadata_for_plot')
+@patch('generate_gallery.merge_metadata')
+@patch('generate_gallery.load_folder_metadata')
+@patch('generate_gallery.convert_pdf_to_png')
+@patch('shutil.copy2')
+def test_build_gallery_basic(
+    mock_copy,
+    mock_convert,
+    mock_load_folder,
+    mock_merge,
+    mock_resolve,
+    mock_save_cache,
+    mock_template,
+    tmp_path
+):
+    source_dir = tmp_path / "source"
+    web_dir = tmp_path / "web"
+    source_dir.mkdir()
+    web_dir.mkdir()
+
+    # Create a test PDF
+    pdf_file = source_dir / "test.pdf"
+    pdf_file.write_text("fake pdf content")
+
+    # Create corresponding PNG
+    png_file = source_dir / "test.png"
+    png_file.write_text("fake png content")
+
+    # Mock returns
+    mock_load_folder.return_value = {"folder": "metadata"}
+    mock_merge.return_value = {"merged": "metadata"}
+    mock_resolve.return_value = {"plot": "metadata"}
+    mock_template.render.return_value = "<html>test</html>"
+
+    build_gallery(source_dir, web_dir)
+
+    # Verify mocks were called
+    mock_load_folder.assert_called_once_with(source_dir)
+    mock_convert.assert_called_once_with(pdf_file)
+    mock_copy.assert_called()  # Should be called for PDF and PNG
+    mock_save_cache.assert_called_once()
+
+    # Check HTML file was created
+    html_file = web_dir / "index.html"
+    assert html_file.exists()
+
+
+@patch('generate_gallery.template')
+@patch('generate_gallery.save_metadata_cache')
+@patch('generate_gallery.load_folder_metadata')
+def test_build_gallery_with_subdirs(
+    mock_load_folder,
+    mock_save_cache,
+    mock_template,
+    tmp_path
+):
+    source_dir = tmp_path / "source"
+    web_dir = tmp_path / "web"
+    source_dir.mkdir()
+    web_dir.mkdir()
+
+    # Create subdirectory
+    subdir = source_dir / "subdir"
+    subdir.mkdir()
+
+    mock_load_folder.return_value = {}
+    mock_template.render.return_value = "<html>test</html>"
+
+    build_gallery(source_dir, web_dir)
+
+    # Check subdirectory was created in web
+    web_subdir = web_dir / "subdir"
+    assert web_subdir.exists()
+    assert web_subdir.is_dir()
+
+
+@patch('generate_gallery.needs_update')
+@patch('shutil.copy2')
+def test_build_gallery_skip_up_to_date(mock_copy, mock_needs_update, tmp_path):
+    source_dir = tmp_path / "source"
+    web_dir = tmp_path / "web"
+    source_dir.mkdir()
+    web_dir.mkdir()
+
+    # Create test files
+    pdf_file = source_dir / "test.pdf"
+    png_file = source_dir / "test.png"
+    pdf_file.write_text("pdf")
+    png_file.write_text("png")
+
+    # Create target files
+    web_pdf = web_dir / "test.pdf"
+    web_png = web_dir / "test.png"
+    web_pdf.write_text("pdf")
+    web_png.write_text("png")
+
+    # Mock needs_update to return False (up to date)
+    mock_needs_update.return_value = False
+
+    with patch('generate_gallery.template') as mock_template:
+        mock_template.render.return_value = "<html>test</html>"
+        build_gallery(source_dir, web_dir)
+
+    # copy2 should not be called since files are up to date
+    mock_copy.assert_not_called()
diff --git a/tests/test_metadata.py b/tests/test_metadata.py
index 7a768d6..5dc8a70 100644
--- a/tests/test_metadata.py
+++ b/tests/test_metadata.py
@@ -1,4 +1,5 @@
 import json
+import pytest
 from utils import metadata
 import yaml
 
@@ -22,4 +23,180 @@ def test_load_metadata_file_json(tmp_path):
 def test_load_metadata_file_missing(tmp_path):
     missing_path = tmp_path / 'nope.yaml'
     result = metadata.load_metadata_file(missing_path)
-    assert result == {}
\ No newline at end of file
+    assert result == {}
+
+
+def test_load_metadata_file_yml_extension(tmp_path):
+    data = {'test': 'yml_format'}
+    yml_path = tmp_path / 'meta.yml'
+    yml_path.write_text(yaml.dump(data))
+    result = metadata.load_metadata_file(yml_path)
+    assert result == data
+
+
+def test_load_metadata_file_unknown_format(tmp_path):
+    txt_path = tmp_path / 'meta.txt'
+    txt_path.write_text('some text')
+    result = metadata.load_metadata_file(txt_path)
+    assert result == {}
+
+
+def test_load_metadata_file_malformed_yaml(tmp_path):
+    yaml_path = tmp_path / 'bad.yaml'
+    yaml_path.write_text('invalid: yaml: content: [')
+    with pytest.raises(yaml.YAMLError):
+        metadata.load_metadata_file(yaml_path)
+
+
+def test_load_metadata_file_malformed_json(tmp_path):
+    json_path = tmp_path / 'bad.json'
+    json_path.write_text('{"invalid": json}')
+    with pytest.raises(json.JSONDecodeError):
+        metadata.load_metadata_file(json_path)
+
+
+def test_load_folder_metadata_yaml(tmp_path):
+    data = {'folder': 'metadata'}
+    metadata_path = tmp_path / 'metadata.yaml'
+    metadata_path.write_text(yaml.dump(data))
+    result = metadata.load_folder_metadata(tmp_path)
+    assert result == data
+
+
+def test_load_folder_metadata_yml(tmp_path):
+    data = {'folder': 'metadata_yml'}
+    metadata_path = tmp_path / 'metadata.yml'
+    metadata_path.write_text(yaml.dump(data))
+    result = metadata.load_folder_metadata(tmp_path)
+    assert result == data
+
+
+def test_load_folder_metadata_json(tmp_path):
+    data = {'folder': 'metadata_json'}
+    metadata_path = tmp_path / 'metadata.json'
+    metadata_path.write_text(json.dumps(data))
+    result = metadata.load_folder_metadata(tmp_path)
+    assert result == data
+
+
+def test_load_folder_metadata_missing(tmp_path):
+    result = metadata.load_folder_metadata(tmp_path)
+    assert result == {}
+
+
+def test_get_metadata_file_path_existing_yaml(tmp_path):
+    metadata_path = tmp_path / 'metadata.yaml'
+    metadata_path.write_text('test: data')
+    result = metadata.get_metadata_file_path(tmp_path)
+    assert result == str(metadata_path)
+
+
+def test_get_metadata_file_path_existing_yml(tmp_path):
+    metadata_path = tmp_path / 'metadata.yml'
+    metadata_path.write_text('test: data')
+    result = metadata.get_metadata_file_path(tmp_path)
+    assert result == str(metadata_path)
+
+
+def test_get_metadata_file_path_existing_json(tmp_path):
+    metadata_path = tmp_path / 'metadata.json'
+    metadata_path.write_text('{"test": "data"}')
+    result = metadata.get_metadata_file_path(tmp_path)
+    assert result == str(metadata_path)
+
+
+def test_get_metadata_file_path_none_existing(tmp_path):
+    result = metadata.get_metadata_file_path(tmp_path)
+    expected = str(tmp_path / 'metadata.yaml')
+    assert result == expected
+
+
+def test_merge_metadata():
+    parent = {'project': 'Test', 'version': '1.0', 'author': 'Parent'}
+    child = {'experiment': 'A', 'version': '1.1'}
+    merged = metadata.merge_metadata(parent, child)
+    expected = {'project': 'Test', 'version': '1.1',
+                'author': 'Parent', 'experiment': 'A'}
+    assert merged == expected
+
+
+def test_merge_metadata_empty_parent():
+    parent = {}
+    child = {'experiment': 'A', 'version': '1.1'}
+    merged = metadata.merge_metadata(parent, child)
+    assert merged == child
+
+
+def test_merge_metadata_empty_child():
+    parent = {'project': 'Test', 'version': '1.0'}
+    child = {}
+    merged = metadata.merge_metadata(parent, child)
+    assert merged == parent
+
+
+def test_resolve_metadata_for_plot_with_specific_yaml(tmp_path):
+    # Create plot-specific metadata file
+    plot_path = tmp_path / 'test_plot.pdf'
+    plot_metadata_path = tmp_path / 'test_plot.yaml'
+    plot_metadata = {'specific': 'plot_data', 'override': 'plot_value'}
+    plot_metadata_path.write_text(yaml.dump(plot_metadata))
+
+    inherited = {'general': 'data', 'override': 'inherited_value'}
+    result = metadata.resolve_metadata_for_plot(plot_path, inherited)
+
+    expected = {'general': 'data',
+                'override': 'plot_value', 'specific': 'plot_data'}
+    assert result == expected
+
+
+def test_resolve_metadata_for_plot_with_specific_json(tmp_path):
+    plot_path = tmp_path / 'test_plot.pdf'
+    plot_metadata_path = tmp_path / 'test_plot.json'
+    plot_metadata = {'specific': 'plot_data_json'}
+    plot_metadata_path.write_text(json.dumps(plot_metadata))
+
+    inherited = {'general': 'data'}
+    result = metadata.resolve_metadata_for_plot(plot_path, inherited)
+
+    expected = {'general': 'data', 'specific': 'plot_data_json'}
+    assert result == expected
+
+
+def test_resolve_metadata_for_plot_no_specific(tmp_path):
+    plot_path = tmp_path / 'test_plot.pdf'
+    inherited = {'general': 'data', 'inherited': 'value'}
+    result = metadata.resolve_metadata_for_plot(plot_path, inherited)
+
+    # Should return copy of inherited metadata
+    assert result == inherited
+    assert result is not inherited  # Should be a copy
+
+
+def test_save_metadata_cache(tmp_path):
+    cache_data = {
+        'plot1': {'title': 'Plot 1', 'author': 'Test'},
+        'plot2': {'title': 'Plot 2', 'experiment': 'B'}
+    }
+
+    metadata.save_metadata_cache(tmp_path, cache_data)
+
+    cache_file = tmp_path / 'meta_cache.json'
+    assert cache_file.exists()
+
+    with cache_file.open('r') as f:
+        loaded_data = json.load(f)
+
+    assert loaded_data == cache_data
+
+
+def test_save_metadata_cache_empty(tmp_path):
+    cache_data = {}
+    metadata.save_metadata_cache(tmp_path, cache_data)
+
+    cache_file = tmp_path / 'meta_cache.json'
+    assert cache_file.exists()
+
+    with cache_file.open('r') as f:
+        loaded_data = json.load(f)
+
+    assert loaded_data == {}