Rethinking Serverless Application Workflows from a Testing Perspective

Phase 1: Requirements

Architecture Overview

• Batch processing workflow using AWS Lambda and Step Functions.
• Three states in a straight line.
• Unit tests for each Lambda function, but manual testing for Step Functions workflow.

Testing Goals

• Automate Step Functions workflow testing.
• Ensure input and output values match expected values.
• Integrate tests into CI/CD pipeline using GitHub Actions.
• Avoid deploying to a real AWS environment for testing.

Phase 2: Plan

Tools and Technologies

• Step Functions Local: For running and testing Step Functions locally.
• GitHub Actions: For CI/CD workflow automation.
• Localstack or similar: To simulate AWS Lambda locally.

GitHub Actions Workflow

• Set up workflow to run tests on push or pull requests.
• Use Step Functions Local Docker image for local testing environment.
• Use Localstack for Lambda simulation.
• https://www.localstack.cloud/
• Import Step Functions definition and run workflow locally.
• Verify input and output values of each state.

Steps in the Workflow

• [ 1 ] Start Containers:
• Pull and start Step Functions Local Docker image.
• Set up Localstack for Lambda simulation.
• [ 2 ] Import Step Functions Definition:
• Import state machine definition into local environment.
• [ 3 ] Run Workflow:
• Trigger Step Functions workflow using local endpoint.
• [ 4 ] Validate Results:
• Check input and output values against expected values.
• [ 5 ] Report Results:
• Generate a report or status indicating test success or failure.

How to Test Serverless Architecture?

Introduction

• Serverless architecture offers significant benefits, enabling quick delivery of value to customers.
• The focus here is on testing from a testing perspective, rather than system performance or cost.

Why Do We Need Testing?

• Testing helps us understand, predict, and control system behavior.
• It allows us to identify and quantify system risks.
• Writing tests helps us better understand requirements.
• Testing ensures reproducibility and explainability of results.
• The primary goal of testing is to reduce unknown risks.

Types of Tests

• Unit Tests: Test individual components or functions in isolation.
• Integration Tests: Test the interaction between combined components.
• Logic Tests: Verify the correctness of business logic.
• Workflow Tests: Test the end-to-end flow of a process or workflow.
• API Tests: Test the functionality and reliability of APIs.

Recommendation

• It is important to be aware of different test types and their purposes and goals.
• Understanding these test types will help in designing effective testing strategies for serverless architectures.

Separate Processing for Easier Testing

Key Points

• Easy-to-Test Units: Units that are easy to test are also easy to understand.
• System Clarity: When a system is designed with separate, testable units, it naturally shows what it does, when it does it, and why it does it.
• Avoiding Complexity: If something is hard to test, it likely means there is too much responsibility and logic concentrated in one place.

Example Comparison

• Less Architecture: A single Lambda function handles both getting data from other servers and processing/storing it in DynamoDB.
• Right Architecture: Separate Lambda functions for each operation (getting data and processing/storing data).

Benefits of Separation

• Easier to test each part individually.
• When an error occurs, it is easier to pinpoint the exact location of the problem.
• Reduces the time from error occurrence to error identification and fix.

General Principle

• Dividing Methods: The same principle of dividing methods applies across different programming languages (e.g., Python, Ruby, Go).
• Small Units: Identify what you consider to be small, testable units and apply this division principle accordingly.

Testing Perspective in System Design

• Identifying Weak Points: From a testing perspective, it is easy to identify weak points, such as too much responsibility in one place.
• Reducing Error Detection Time: High testability helps reduce the time from error occurrence to error detection and fix, similar to reducing the development cycle.
• Quick Delivery: High testability contributes to quicker system delivery.

Key Points to Consider When Building Serverless Architecture from a Testing Perspective

• Separate Processing: Easier to test units are easier to understand. Separating processes helps identify weak points and reduces error detection time.
• Avoiding Complexity: Concentrated responsibility and logic in one place make testing difficult. Separate processes to simplify testing and troubleshooting.
• High Testability: Contributes to quicker system delivery and reduced development cycles.

Final Goal

• The ultimate goal for engineers is to deliver value to users.
• Always keep user value in mind to ensure successful outcomes.
• Encouraged discussion and collaboration to share insights and improve testing practices.