Runner Architecture

The runner package has two execution paths:

• Local testing - DurableFunctionLocalTestRunner runs the handler in process and injects InMemoryServiceClient so checkpoint operations are processed locally.
• Cloud testing - DurableFunctionCloudTestRunner invokes a qualified Lambda function and polls for durable execution completion.

Local execution flows through these major components:

1. DurableTestRunner starts execution through Executor.
2. Executor creates an Execution and schedules the initial invocation on the local asyncio event loop.
3. During execution, checkpoint updates are handled by CheckpointProcessor.
4. Operation-specific validators and processors transform updates into step, wait, callback, context, and execution operations.
5. ExecutionNotifier publishes lifecycle events.
6. Executor observes those events asynchronously and updates execution state until completion.
7. DurableFunctionTestResult exposes status, result payloads, and named operation lookup helpers.

Architecture diagrams:

• Durable Functions Python Test Framework Architecture
• Event Flow Sequence Diagram