251102 Rethinking Serverless Application Workflows from a Testing Perspective

2025/11/02 (日) AWS Community Day 2025 Hong Kongにて発表した登壇資料。
https://awscommunity.hk/

Transcript

1. SPEAKER Takumi Abe JAWS-UG Oita, AWS Community Builder(Serverless) Where Ideas Meet Action Rethinking Serverless Application Workflows from a Testing Perspective
3. Abetaku (Takumi Abe)
 { 　"Community": [ 　　"JAWS-UG Oita", 　　"AWS Community Builder(Serverless)", 　　"Fukuoka Cloud UG", 　　"Main Street revitalization in Oita, Japan." 　], "Company": "KDDI Agile Development Center", "Work": "Software Engineer", 　"LinkdIn": "east-takumi" } }
4. Agenda
 1. Context - Click-Through, Not Scripted 2. Try - Workflow Tests with SFN Local 3. Reflections - Rethinking from a testing perspective
5. In My Project…
 • Develop a new batch process on a serverless architecture • A simple three-state Step Functions workflow (all Lambda) • Unit tests exist per state, but end-to-end state machine testing is manual with visual I/O verification. Context- Click-Through, Not Scripted

6. In My Project…
 • Develop a new batch process on a serverless architecture • A simple three-state Step Functions workflow (all Lambda) • Unit tests exist per state, but end-to-end state machine testing is manual with visual I/O verification. Context- Click-Through, Not Scripted
 Wait—now I really want this automated.(^◇^;)

7. Why no automation?
 • Team Context ◦ Limited serverless testing beyond UT (integration/E2E) • Project Context ◦ Serverless spec changes are expected to be rare Context- Click-Through, Not Scripted

8. Development State & Requirements
 • Lambda + Step Functions, defined via AWS SAM • Workflow: 3 states in a straight line, all built as Lambda • Tests: for each state, assert that inputs/outputs contain the expected values, etc. • CI: self-contained in GitHub Actions (no deploy to AWS) Try - Workflow Tests with SFN Local

9. Step Functions Local
 A local emulator (JAR/Docker) to run Step Functions on your machine.Integrations can hit mock responses, local endpoints, or real AWS. Try - Workflow Tests with SFN Local
 Source:DevelopersIO https://dev.classmethod.jp/articles/step-functions-local-tried/
10. System Architecture
 Try - Workflow Tests with SFN Local

11. • Unsupported and not production-parity (dev only) ◦ Keep sensitive data out ◦ Low ops fidelity (IAM, CloudWatch etc.) • Prod use → LocalStack ◦ Recreates many AWS services—including Step Functions—in one local environment ◦ Easy to plug into CI ▪ →note that some features aren’t available for free. However…
 Try - Workflow Tests with SFN Local

12. Why do we even need tests?
 • Understand to system behavior ◦ →Tests are tools for understanding • Build Trust through Reproducibility & Explainability • Grasp the Risks ◦ →If we can quantify the risk, can devise countermeasures Trust. Predict. Observe. The better the path, the more risk becomes visible and manageable. Reflections - Rethinking from a testing perspective
 https://www.amazon.co.jp/dp/B074BQQ96X?ref =ppx_yo2ov_dt_b_fed_digi_asin_title_351
13. Design Tests: Layers × Boundaries
 • Different tests, different purposes ◦ Logic, contracts, connections, workflows, and user paths—each has its own test. • Boundaries ◦ Cut at observable units; the system explains itself ◦ Hard to test → Responsibility is piled up Reflections - Rethinking from a testing perspective

14. Example
 Fetch/process data from an other server and upload results to DynamoDB
 Reflections - Rethinking from a testing perspective

15. Tests as a Design Feedback Loop
 • Expose design weaknesses (concentrated responsibility, fuzzy boundaries, scattered side effects) • Enable fearless refactoring with an automated safety net • Shorten cycle time ◦ change small → get fast certainty → ship Reflections - Rethinking from a testing perspective

16. Tests as a Design Feedback Loop
 • Expose design weaknesses (concentrated responsibility, fuzzy boundaries, scattered side effects) • Enable fearless refactoring with an automated safety net • Shorten cycle time ◦ change small → get fast certainty → ship High testability leads to better design —and faster delivery. Reflections - Rethinking from a testing perspective

17. Don't strive for perfection too much
 • Progress over perfection. • Ship, learn, iterate. • Continuously reassess what “user value” means. →Testing and serverless are means to deliver “user value” Reflections - Rethinking from a testing perspective

18. Takeaways
 • SFn workflow tests are doable with SFn Local, LocalStack • Clear state responsibilities → easier, reliable tests • Design for testability → ship faster • Let’s build better serverless testing together
19. JAWS DAYS 2026 to be held
 March 7, 2026