feat: Implement comprehensive Testing Architecture Enhancement

Establishes robust testing framework with clean architecture patterns:

## Phase 1: Test Infrastructure Foundation
- Global test configuration with pytest.ini and conftest.py
- Isolated test workspaces and environment management
- Comprehensive fixture library for all test types
- Test requirements and dependency management

## Phase 2: Advanced Testing Patterns
- Test builders using builder pattern for domain objects
- Mock factories for repositories, services, and configs
- API response builders for external system simulation
- Enhanced unit tests with proper mocking and isolation

## Phase 3: Test Performance and Quality
- Performance testing framework with benchmarks
- Memory usage monitoring and leak detection
- Custom assertions for domain-specific validation
- Parametrized testing for comprehensive coverage

## Phase 4: CI/CD Integration
- GitHub Actions workflow for automated testing
- Multi-stage testing: unit → integration → e2e → performance
- Code quality checks with flake8, mypy, black, isort
- Security scanning with safety and bandit

## Testing Architecture Benefits
✅ 100+ new test infrastructure components
✅ Standardized test organization (unit/integration/e2e)
✅ Mock-based testing with no external dependencies
✅ Performance regression detection
✅ Comprehensive fixture library
✅ CI/CD pipeline with quality gates

The testing framework supports the domain logic separation and provides
a solid foundation for maintaining high code quality as the system evolves.

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

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

tests/conftest.py

@@ -0,0 +1,296 @@
+"""
+Global test configuration and fixtures for MarkiTect project.
+
+Provides shared fixtures, utilities, and configuration for all test types.
+"""
+
+import pytest
+import tempfile
+import shutil
+import asyncio
+from pathlib import Path
+from unittest.mock import Mock, AsyncMock
+from typing import Generator, Dict, Any
+import sqlite3
+import os
+
+
+@pytest.fixture(scope="session")
+def event_loop():
+    """Create an instance of the default event loop for the test session."""
+    loop = asyncio.new_event_loop()
+    yield loop
+    loop.close()
+
+
+@pytest.fixture(scope="session")
+def test_workspace() -> Generator[Path, None, None]:
+    """Create isolated test workspace for file operations."""
+    temp_dir = tempfile.mkdtemp(prefix="markitect_test_")
+    workspace_path = Path(temp_dir)
+
+    # Create subdirectories
+    (workspace_path / "documents").mkdir()
+    (workspace_path / "cache").mkdir()
+    (workspace_path / "workspaces").mkdir()
+
+    yield workspace_path
+
+    # Cleanup
+    shutil.rmtree(temp_dir, ignore_errors=True)
+
+
+@pytest.fixture
+def test_database_path(test_workspace) -> Path:
+    """Provide path for test database."""
+    return test_workspace / "test.db"
+
+
+@pytest.fixture
+def mock_database():
+    """Provide mocked database for testing."""
+    mock_db = Mock()
+    mock_cursor = Mock()
+    mock_db.cursor.return_value = mock_cursor
+    mock_db.execute.return_value = mock_cursor
+    mock_cursor.fetchone.return_value = None
+    mock_cursor.fetchall.return_value = []
+    mock_cursor.lastrowid = 1
+    return mock_db
+
+
+@pytest.fixture
+def mock_http_client():
+    """Provide mocked HTTP client for API tests."""
+    mock_client = Mock()
+    mock_response = Mock()
+    mock_response.status_code = 200
+    mock_response.json.return_value = {"status": "success"}
+    mock_response.text = '{"status": "success"}'
+    mock_client.get.return_value = mock_response
+    mock_client.post.return_value = mock_response
+    mock_client.put.return_value = mock_response
+    mock_client.delete.return_value = mock_response
+    return mock_client
+
+
+@pytest.fixture
+def mock_async_http_client():
+    """Provide mocked async HTTP client for API tests."""
+    mock_client = AsyncMock()
+    mock_response = AsyncMock()
+    mock_response.status = 200
+    mock_response.json = AsyncMock(return_value={"status": "success"})
+    mock_response.text = AsyncMock(return_value='{"status": "success"}')
+    mock_client.get.return_value = mock_response
+    mock_client.post.return_value = mock_response
+    mock_client.put.return_value = mock_response
+    mock_client.delete.return_value = mock_response
+    return mock_client
+
+
+@pytest.fixture
+def test_config(test_workspace) -> Dict[str, Any]:
+    """Provide test configuration dictionary."""
+    return {
+        "workspace_dir": str(test_workspace / "workspaces"),
+        "database_path": str(test_workspace / "test.db"),
+        "cache_dir": str(test_workspace / "cache"),
+        "gitea_url": "http://test-gitea.com",
+        "gitea_token": "test-token",
+        "repo_owner": "test",
+        "repo_name": "repo",
+        "log_level": "DEBUG"
+    }
+
+
+@pytest.fixture
+def clean_environment():
+    """Provide clean environment variables for testing."""
+    original_env = dict(os.environ)
+
+    # Clear relevant environment variables
+    test_env_vars = [
+        "MARKITECT_WORKSPACE_DIR",
+        "MARKITECT_GITEA_URL",
+        "MARKITECT_GITEA_TOKEN",
+        "MARKITECT_REPO_OWNER",
+        "MARKITECT_REPO_NAME"
+    ]
+
+    for var in test_env_vars:
+        os.environ.pop(var, None)
+
+    yield
+
+    # Restore original environment
+    os.environ.clear()
+    os.environ.update(original_env)
+
+
+@pytest.fixture
+def isolated_environment(test_workspace, clean_environment):
+    """Set up isolated environment for CLI testing."""
+    env = {
+        "MARKITECT_WORKSPACE_DIR": str(test_workspace / "workspaces"),
+        "MARKITECT_GITEA_URL": "http://test-gitea.com",
+        "MARKITECT_GITEA_TOKEN": "test-token",
+        "MARKITECT_REPO_OWNER": "test",
+        "MARKITECT_REPO_NAME": "repo",
+        "PYTHONPATH": "."
+    }
+
+    # Update current process environment
+    for key, value in env.items():
+        os.environ[key] = value
+
+    yield env
+
+
+@pytest.fixture
+def sample_markdown_content():
+    """Provide sample markdown content for testing."""
+    return """---
+title: Test Document
+author: Test Author
+tags: [test, sample]
+---
+
+# Test Document
+
+This is a test document with **bold** and *italic* text.
+
+## Section 1
+
+- Item 1
+- Item 2
+- Item 3
+
+## Section 2
+
+Here's a code block:
+
+```python
+def hello_world():
+    print("Hello, World!")
+```
+
+And a link: [Test Link](https://example.com)
+"""
+
+
+@pytest.fixture
+def sample_issue_data():
+    """Provide sample issue data for testing."""
+    return {
+        "number": 123,
+        "title": "Test Issue",
+        "body": "This is a test issue description",
+        "state": "open",
+        "labels": [
+            {"name": "bug"},
+            {"name": "priority:high"},
+            {"name": "status:in-progress"}
+        ],
+        "milestone": {
+            "id": 1,
+            "title": "Version 1.0",
+            "description": "First release"
+        },
+        "created_at": "2025-01-01T00:00:00Z",
+        "updated_at": "2025-01-01T12:00:00Z"
+    }
+
+
+@pytest.fixture
+def sample_project_data():
+    """Provide sample project data for testing."""
+    return {
+        "name": "Test Project",
+        "description": "A test project for testing",
+        "state": "active",
+        "milestones": [
+            {
+                "id": 1,
+                "title": "Version 1.0",
+                "description": "First release",
+                "due_date": "2025-12-31T23:59:59Z",
+                "state": "open",
+                "open_issues": 5,
+                "closed_issues": 3
+            }
+        ],
+        "kanban_columns": ["Todo", "In Progress", "Review", "Done"],
+        "created_at": "2024-01-01T00:00:00Z",
+        "updated_at": "2025-01-01T00:00:00Z"
+    }
+
+
+# Performance testing fixtures
+@pytest.fixture
+def performance_timer():
+    """Timer fixture for performance testing."""
+    import time
+
+    class Timer:
+        def __init__(self):
+            self.start_time = None
+            self.end_time = None
+
+        def start(self):
+            self.start_time = time.time()
+
+        def stop(self):
+            self.end_time = time.time()
+
+        @property
+        def elapsed(self) -> float:
+            if self.start_time is None:
+                raise ValueError("Timer not started")
+            if self.end_time is None:
+                return time.time() - self.start_time
+            return self.end_time - self.start_time
+
+    return Timer()
+
+
+# Async test helpers
+@pytest.fixture
+def async_test_timeout():
+    """Default timeout for async tests."""
+    return 30.0  # 30 seconds
+
+
+# Test markers configuration
+def pytest_configure(config):
+    """Configure pytest markers."""
+    config.addinivalue_line(
+        "markers", "slow: marks tests as slow (deselect with '-m \"not slow\"')"
+    )
+    config.addinivalue_line(
+        "markers", "integration: marks tests as integration tests"
+    )
+    config.addinivalue_line(
+        "markers", "e2e: marks tests as end-to-end tests"
+    )
+    config.addinivalue_line(
+        "markers", "performance: marks tests as performance tests"
+    )
+    config.addinivalue_line(
+        "markers", "unit: marks tests as unit tests"
+    )
+
+
+# Collection hooks
+def pytest_collection_modifyitems(config, items):
+    """Modify test collection to add markers based on test location."""
+    for item in items:
+        # Add markers based on test file location
+        if "unit" in str(item.fspath):
+            item.add_marker(pytest.mark.unit)
+        elif "integration" in str(item.fspath):
+            item.add_marker(pytest.mark.integration)
+        elif "e2e" in str(item.fspath):
+            item.add_marker(pytest.mark.e2e)
+        elif "performance" in str(item.fspath):
+            item.add_marker(pytest.mark.performance)