Add Unit Tests (#132)

* Add tests and new github workflow

* Add new unit tests

* Add Github CI workflow

* Workflow fix

* Add pytest install to workflow file

* More CI / test updates

* More test cleanup

* Whitespace cleanup and link complexity override

* More whitespace cleanup

* Make lint less strict

* More lint tweaks

tests/test_engine_manager.py

@@ -0,0 +1,239 @@
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from src.engines.engine_manager import EngineManager, EngineDownloadWorker
+
+
+class TestEngineManagerSyncClass:
+    """_sync_class propagates instance attrs to class level."""
+
+    def test_sync_class_propagates_engines_path(self, engine_manager_instance):
+        assert EngineManager.engines_path == engine_manager_instance.engines_path
+
+    def test_sync_class_noop_when_no_instance(self):
+        orig = EngineManager._default_instance
+        try:
+            EngineManager._default_instance = None
+            EngineManager.engines_path = 'original'
+            EngineManager._sync_class()
+            assert EngineManager.engines_path == 'original'
+        finally:
+            EngineManager._default_instance = orig
+            EngineManager._sync_class()
+
+    def test_supported_engines_returns_list(self):
+        engines = EngineManager.supported_engines()
+        assert len(engines) >= 2
+
+
+class TestEngineClassMapping:
+    """Mapping file extensions and names to engine classes."""
+
+    def test_engine_class_with_name_finds_blender(self, engine_manager_instance):
+        cls = EngineManager.engine_class_with_name('blender')
+        assert cls is not None
+        assert cls.__name__ == 'Blender'
+
+    def test_engine_class_with_name_finds_ffmpeg(self, engine_manager_instance):
+        cls = EngineManager.engine_class_with_name('ffmpeg')
+        assert cls is not None
+        assert cls.__name__ == 'FFMPEG'
+
+    def test_engine_class_with_name_returns_none_for_unknown(self, engine_manager_instance):
+        cls = EngineManager.engine_class_with_name('nonexistent')
+        assert cls is None
+
+    def test_engine_class_with_name_case_insensitive(self, engine_manager_instance):
+        cls = EngineManager.engine_class_with_name('BLENDER')
+        assert cls is not None
+        assert cls.__name__ == 'Blender'
+
+    def test_engine_class_for_project_path_no_engines_path(self, engine_manager_instance):
+        engine_manager_instance.engines_path = None
+        with pytest.raises(FileNotFoundError):
+            EngineManager.engine_class_for_project_path('test.blend')
+
+
+class TestGetInstalledEngineData:
+    """Parsing directory listings for managed engines."""
+
+    def test_get_installed_engine_data_no_path(self, engine_manager_instance):
+        engine_manager_instance.engines_path = None
+        with pytest.raises(FileNotFoundError):
+            EngineManager.get_installed_engine_data()
+
+    def test_get_installed_engine_data_empty_dir(self, engine_manager_instance, tmp_path):
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+        result = EngineManager.get_installed_engine_data(ignore_system=True)
+        assert result == []
+
+    @patch('src.engines.engine_manager.os.listdir')
+    @patch('src.engines.engine_manager.os.path.isdir')
+    def test_parse_managed_engine_directory(
+        self, mock_isdir, mock_listdir, engine_manager_instance, tmp_path,
+    ):
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+        mock_listdir.return_value = ['blender-3.6.0-macos-arm64']
+        mock_isdir.return_value = True
+
+        result = EngineManager.get_installed_engine_data(ignore_system=True)
+
+        assert len(result) == 1
+        assert result[0]['engine'] == 'blender'
+        assert result[0]['version'] == '3.6.0'
+        assert result[0]['system_os'] == 'macos'
+        assert result[0]['cpu'] == 'arm64'
+        assert result[0]['type'] == 'managed'
+
+    @patch('src.engines.engine_manager.os.listdir')
+    @patch('src.engines.engine_manager.os.path.isdir')
+    def test_filter_by_engine_name(
+        self, mock_isdir, mock_listdir, engine_manager_instance, tmp_path,
+    ):
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+        mock_listdir.return_value = ['blender-3.6.0-macos-arm64', 'ffmpeg-6.0-macos-arm64']
+        mock_isdir.return_value = True
+
+        blender_only = EngineManager.get_installed_engine_data(
+            filter_name='blender', ignore_system=True)
+        assert len(blender_only) == 1
+        assert blender_only[0]['engine'] == 'blender'
+
+
+class TestNewestInstalledEngineData:
+    """Filtering by system and CPU."""
+
+    @patch('src.engines.engine_manager.current_system_os')
+    @patch('src.engines.engine_manager.current_system_cpu')
+    def test_newest_filters_by_system_and_cpu(
+        self, mock_cpu, mock_os, engine_manager_instance, tmp_path,
+    ):
+        mock_os.return_value = 'macos'
+        mock_cpu.return_value = 'arm64'
+
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+        dirs = [
+            'blender-3.6.0-macos-arm64',
+            'blender-4.0.0-linux-x86_64',
+            'blender-4.1.0-macos-arm64',
+        ]
+
+        with (patch('src.engines.engine_manager.os.listdir', return_value=dirs),
+              patch('src.engines.engine_manager.os.path.isdir', return_value=True)):
+            result = EngineManager.newest_installed_engine_data(
+                'blender', ignore_system=True)
+
+        assert result['version'] == '4.1.0'
+        assert result['system_os'] == 'macos'
+        assert result['cpu'] == 'arm64'
+
+    def test_newest_returns_empty_on_no_match(self, engine_manager_instance, tmp_path):
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+
+        result = EngineManager.newest_installed_engine_data('nonexistent')
+        assert result == []
+
+
+class TestIsVersionInstalled:
+    """Checking whether a specific version is installed."""
+
+    @patch('src.engines.engine_manager.current_system_os')
+    @patch('src.engines.engine_manager.current_system_cpu')
+    def test_finds_matching_version(
+        self, mock_cpu, mock_os, engine_manager_instance, tmp_path,
+    ):
+        mock_os.return_value = 'macos'
+        mock_cpu.return_value = 'arm64'
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+
+        dirs = ['blender-3.6.0-macos-arm64', 'blender-4.1.0-macos-arm64']
+
+        with (patch('src.engines.engine_manager.os.listdir', return_value=dirs),
+              patch('src.engines.engine_manager.os.path.isdir', return_value=True)):
+            result = EngineManager.is_version_installed('blender', '3.6.0')
+
+        assert result is not False
+
+    @patch('src.engines.engine_manager.current_system_os')
+    @patch('src.engines.engine_manager.current_system_cpu')
+    def test_returns_false_on_no_match(
+        self, mock_cpu, mock_os, engine_manager_instance, tmp_path,
+    ):
+        mock_os.return_value = 'macos'
+        mock_cpu.return_value = 'arm64'
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+
+        result = EngineManager.is_version_installed('blender', '99.0.0')
+        assert result is False
+
+
+class TestDeleteEngineDownload:
+    """Deleting a managed engine directory."""
+
+    @patch('src.engines.engine_manager.shutil.rmtree')
+    @patch('src.engines.engine_manager.current_system_os', return_value='macos')
+    @patch('src.engines.engine_manager.current_system_cpu', return_value='arm64')
+    def test_delete_managed_engine(
+        self, mock_cpu, mock_os, mock_rmtree, engine_manager_instance, tmp_path,
+    ):
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+        engines_dir = tmp_path / 'engines' / 'blender-3.6.0-macos-arm64'
+        engines_dir.mkdir(parents=True)
+        (engines_dir / 'Blender').write_text('fake binary')
+        result = EngineManager.delete_engine_download('blender', '3.6.0')
+        assert result is True
+        mock_rmtree.assert_called_once_with(str(engines_dir), ignore_errors=False)
+
+    def test_delete_nonexistent_engine(self, engine_manager_instance, tmp_path):
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+
+        result = EngineManager.delete_engine_download('nonexistent', '1.0.0')
+        assert result is False
+
+
+class TestActiveDownloads:
+    """Background download tracking."""
+
+    def test_active_downloads_empty_initially(self, engine_manager_instance):
+        assert EngineManager.active_downloads() == []
+
+    def test_download_tasks_tracked(self, engine_manager_instance):
+        task = MagicMock(spec=EngineDownloadWorker)
+        task.is_alive.return_value = True
+        task.name = 'blender-4.0.0-macos-arm64'
+        engine_manager_instance.download_tasks.append(task)
+
+        active = EngineManager.active_downloads()
+        assert len(active) == 1
+
+
+class TestCreateWorker:
+    """Creating worker instances for render jobs."""
+
+    def test_create_worker_raises_when_no_engines_installed(self, engine_manager_instance, tmp_path):
+        engine_manager_instance.engines_path = str(tmp_path / 'engines')
+
+        with patch.object(engine_manager_instance, '_get_installed_engine_data', return_value=[]):
+            with pytest.raises(FileNotFoundError, match='Cannot find any installed'):
+                EngineManager.create_worker(
+                    'blender',
+                    input_path=tmp_path / 'test.blend',
+                    output_path=tmp_path / 'output',
+                )
+
+    def test_create_worker_raises_for_unknown_engine(self, engine_manager_instance):
+        with pytest.raises(AttributeError):
+            EngineManager.create_worker(
+                'nonexistent',
+                input_path='/tmp/test.blend',
+                output_path='/tmp/output',
+            )
+
+
+class TestDownloadableEngines:
+    """Engines with a downloader."""
+
+    def test_downloadable_engines_returns_list(self, engine_manager_instance):
+        engines = EngineManager.downloadable_engines()
+        assert isinstance(engines, list)