Add parallel test execution with pytest-xdist

Implements per-worker database isolation for parallel test runs:
- Add pytest-xdist and pytest-cov to test dependencies
- Configure Makefile to run tests with -n auto flag
- Update test.ini to use environment variable for database path
- Create conftest.py with per-worker database isolation
- Enable SQLite WAL mode for better concurrency
- Auto-cleanup test databases after completion

Expected performance improvement similar to make_post_sell (~16x speedup).

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Makefile

@@ -113,11 +113,10 @@ activate:
 	@echo "To activate the virtual environment, run:"
 	@echo "  source $(VENV_DIR)/bin/activate"
 
-# Run the test suite (installs test dependencies if needed)
 # Run the test suite (installs test dependencies if needed)
 test: install-source-dev-and-test
-	@echo "Running tests..."
+	@echo "Running tests in parallel..."
-	$(VENV_DIR)/bin/py.test
+	$(VENV_DIR)/bin/py.test -n auto
 
 # Start a simple HTTP server (for serving static files like index.html)
 http: venv

remarkbox/tests/conftest.py

@@ -0,0 +1,77 @@
+"""
+Pytest configuration for parallel test execution.
+
+This module configures pytest-xdist to use isolated databases per worker
+to avoid SQLite locking issues during parallel test runs.
+"""
+import os
+import pytest
+
+
+def pytest_configure(config):
+    """
+    Configure test database isolation for parallel execution.
+
+    Each pytest-xdist worker gets its own database file to prevent
+    SQLite locking conflicts. WAL mode is enabled for better concurrency.
+    """
+    # Get worker ID (e.g., "gw0", "gw1", etc.) for pytest-xdist
+    worker_id = os.environ.get("PYTEST_XDIST_WORKER", "master")
+
+    # Set unique database path for this worker
+    test_db_path = f"test-remarkbox_{worker_id}.sqlite"
+    os.environ["TEST_DATABASE_PATH"] = test_db_path
+
+    # Store for cleanup
+    config.test_db_path = test_db_path
+
+
+def pytest_unconfigure(config):
+    """Clean up test database after all tests complete."""
+    if hasattr(config, "test_db_path"):
+        db_path = config.test_db_path
+        if os.path.exists(db_path):
+            try:
+                os.remove(db_path)
+            except Exception as e:
+                print(f"Warning: Could not remove test database {db_path}: {e}")
+
+
+@pytest.fixture(scope="session")
+def db_engine(request):
+    """
+    Create a SQLAlchemy engine with WAL mode enabled for concurrency.
+
+    WAL (Write-Ahead Logging) mode allows multiple readers while a writer
+    is active, improving parallel test performance.
+    """
+    from sqlalchemy import create_engine, event
+
+    # Use worker-specific database
+    worker_id = os.environ.get("PYTEST_XDIST_WORKER", "master")
+    db_path = f"test-remarkbox_{worker_id}.sqlite"
+    db_url = f"sqlite:///{db_path}"
+
+    engine = create_engine(
+        db_url,
+        echo=False,
+        # Important: Use NullPool to avoid connection sharing issues
+        poolclass=__import__("sqlalchemy.pool", fromlist=["NullPool"]).NullPool,
+    )
+
+    # Enable WAL mode for better concurrency
+    @event.listens_for(engine, "connect")
+    def set_sqlite_pragma(dbapi_conn, connection_record):
+        cursor = dbapi_conn.cursor()
+        # Enable WAL mode for concurrent access
+        cursor.execute("PRAGMA journal_mode=WAL")
+        # Increase cache size for better performance
+        cursor.execute("PRAGMA cache_size=-64000")  # 64MB
+        # Enable foreign keys
+        cursor.execute("PRAGMA foreign_keys=ON")
+        cursor.close()
+
+    yield engine
+
+    # Cleanup
+    engine.dispose()

requirements-test.txt

@@ -1,5 +1,7 @@
 # testing.
 pytest
+pytest-cov
+pytest-xdist  # Parallel test execution
 nose
 mock
 webtest

test.ini

@@ -2,12 +2,12 @@
 
 [alembic]
 script_location = remarkbox:scripts/alembic
-sqlalchemy.url = sqlite:///%(here)s/test-remarkbox.sqlite
+sqlalchemy.url = sqlite:///%(here)s/${TEST_DATABASE_PATH:-test-remarkbox.sqlite}
 
 [app:main]
 use = egg:remarkbox
 
-sqlalchemy.url = sqlite:///%(here)s/test-remarkbox.sqlite
+sqlalchemy.url = sqlite:///%(here)s/${TEST_DATABASE_PATH:-test-remarkbox.sqlite}
 #sqlalchemy.url = postgres://localhost/remarkbox_test
 
 ###