Workshop - Mocks as Code. Modeling services in Config Management integration tests

When managing service configurations at scale, we often need to automate testing of these configurations. In software integration testing, we can use Testcontainers - a popular framework for Docker and other container engines. For public cloud environments, there is LocalStack. And for API service providers, we have WireMock. Can we use the same toolchain for configuration management? If you use modern Infrastructure-as-Code tools like Pulumi, yes!

In this edition, we will use Java or Kotlin for EVERYTHING, from the application itself and all the way up to Infrastructure as Code definitions and tests.

In this workshop, we will go through the following topics:
1. Containerizing Spring app development
2. Integration testing with Testcontainers and LocalStack
3. Mocking APIs with WireMock
4. Infrastructure as Code (IaC) with Pulumi and Pulumi for Java
5. Testing IaC locally, with all tools above combined

See https://github.com/oleg-nenashev/mocks-as-code-demo for the demo repository we will be using in this workshop. It also contains all the links to the used tools and additional learning materials.

Copyright Notice: Gradle, Inc. Gradle®, Develocity®, Build Scan®, and the Gradlephant logo are registered trademarks of Gradle, Inc. "Gradle" means "Gradle Build Tool" and does not reference Gradle, Inc. and/or its subsidiaries

Transcript

1. Oleg Nenashev, @oleg_nenashev CNCF Ambassador
2. NOTE: • This presentation was modified on 08 Oct 2025, to exclude trademarks and IP of Gradle Inc, as per request from the company • The content is mostly retained, except for the observability section • Gradle®, Develocity®, Build Scan®, and the Gradlephant logo are registered trademarks of Gradle, Inc. "Gradle" means "Gradle Build Tool" and does not reference Gradle, Inc. and/or its subsidiaries.
3. > whoami @oleg_nenashev oleg-nenashev Dr. Nenashev / Mr. Jenkins Community builder Developer Tools Hacker #RussiansAgainstPutin #StandWithUkraine
4. Async Q&A: Testcontainers Slack speakerdeck.com/onenashev
5. 5 Staging & QA Tests Build Integration tests Build Tests Gaining confidence in you software “Shift Left” with modern tools
6. “Shift Left”, they said? YAML, they gave? 6
7. 7 Java All the Way Down Up Application Unit Tests Build Definition and Pipelines Integration Tests Infrastructure-as-Code Deployment Pipelines Deployment Tests Production Health Checks Java the stack up all the way
8. Today 8 1. Containerizing Spring App Development 2. Integration testing with Testcontainers and LocalStack 3. Mocking APIs with WireMock 4. Infrastructure as Code (IaC) with Pulumi 5. Testing IaC locally 6. Advanced Troubleshooting Localstack
9. Our Repository github.com/oleg-nenashev/mocks-as-code-demo git clone it
10. Workshop Prerequisites • Internet :( • Java 17 & your favorite IDE • Testcontainers-compatible Docker environment ◦ Tested on: Docker Desktop ◦ You can use: Podman, Colima, Rancher Desktop (list) ◦ OR: Testcontainers Cloud • Pulumi CLI + registration ◦ Guide: www.pulumi.com/docs/install/ 10
11. Our Application 11
12. 12 AWS S3 SQS External API Our Application
13. Credits 13 • Siva Prasad Reddy and Oleg Shelajev, Docker • The demos are based on: ◦ github.com/testcontainers/tc-guide-testing-aws-service-integrations-using-loca lstack ◦ github.com/testcontainers-community/testcontainers-wiremock-demo
14. Integration Testing? 14 github.com/oleg-nenashev/mocks-as-code-demo/ tree/main/2_api_mocking
18. Ways to do API integration testing 1. Testing against Production/Staging servers 2. Testing against a simplified/containerized instance (e.g. Testcontainers) 3. Modeling (aka Mocking) at the API provider level (e.g. WireMock or Microcks) 4. Mocking at the code level Slow Fast Nope Accu- rate * For Testcontainers, see the slides
19. 19 https://martinfowler.com/articles/ mocksArentStubs.html
21. 21 SDKs testcontainers.org … and
22. 22 github.com/testcontainers/ testcontainers-go
23. Example - Java 23
24. 24 LOCAL STACK LocalStack Module K3s Module
25. 25 Localstack www.localstack.cloud
26. LocalStack • Local AWS Services emulation OR mocking • “awslocal” CLI utility • SDKs for languages and test frameworks 26 docs.localstack.cloud/
27. 27 x.com/dastbe/status/1303858170155081728
28. Some of Them 28 • Emulated: S3, SQS, … • Mocked: EC2 (in the FOSS lib) • Thoughts & Prayers: AWS GreenShift ;) • …
29. Demo Time 29 github.com/oleg-nenashev/mocks-as-code-demo/ tree/main/1_application
30. No Implementation? 30 Fake it until you “$ make it”
31. Ways to do API integration testing 1. Testing against Production/Staging servers 2. Testing against a simplified/containerized instance (e.g. Testcontainers) 3. Modeling (aka Mocking) at the API provider level (e.g. WireMock or Microcks) 4. Mocking at the code level Slow Fast Nope Accu- rate * For Testcontainers, see the slides
32. wiremock.org/docs/stubbing IF (request_url) THEN (response) * * it gets MUCH more complex WireMock Config JSON: Client library response request Client App Mock API Server HTTP/2 API Mocking 101
33. API Mocking Tools Main implementation in Java Native lib, Docker images and Testcontainers modules Support for GraalVM Rich Ecosystem Sandbox CNCF Project Golang / Microservice arch Docker image, Testcontainers module, All-in K8s Charts Less Rich Ecosystem
34. WireMock Ecosystem & Features wiremock.org/docs
35. WireMock Ecosystem wiremock.org/docs
36. WireMock in Java wiremock.org/docs/stubbing
37. WireMock Ecosystem / Java • Java • Kotlin • Scala • Groovy • Clojure • (?)Android 37 • JUnit 4/5 • Testcontainers • Sprint Boot • Spring Cloud Contract • Quarkus • Maven / Gradle Build Tool • Spock • Pact
38. Example - JUnit 5 38
39. 39 WireMock has an official Testcontainers module! testcontainers.com/modules/wiremock
40. Demo Time 40 github.com/oleg-nenashev/mocks-as-code-demo
41. 41 Infrastructure-as-Code, for real
43. 43 And more constructive!
44. HOWTO: JavaDev-Ops 44
45. Enter -as-Code Tools! • Infrastructure as Real Code • SDKs for programming languages • Standard IDEs • Standard Developer Tools • Extensibility via libraries 45
46. • Open-Ecosystem Tool for Infra-as-Code • Open Source SDKs 46
47. • Multiple destinations 47 www.pulumi.com
48. • 120+ extensions: www.pulumi.com/registry/ 48 www.pulumi.com
49. Pulumi for Java 49 pulumi.com/docs/languages-sdks/java/
50. build.gradle 50
51. 51 Java All the Way Down Up Application Unit Tests Build Definition and Pipelines Integration Tests Infrastructure-as-Code Deployment Pipelines Deployment Tests Production Health Checks Java the stack up all the way
52. 52 Localstack
53. Pulumi Local • github.com/localstack/pulumi-local • Setting the environment and the configuration right • Just a script 53 Localstack
56. Hacking Time! 56 github.com/oleg-nenashev/mocks-as-code-demo/ tree/main/3_deployment
57. When it Goes wrong 57
61. Demo Time 61 github.com/oleg-nenashev/mocks-as-code-demo
62. Lessons Learned 62
63. Beware Pulumi for AWS Native • AWS Native configuration is not applied for endpoints • APIs are slightly different in the package 63
68. 68 Java All the Way Down Up Application Unit Tests Build Definition and Pipelines Integration Tests Infrastructure-as-Code Deployment Pipelines Deployment Tests Production Health Checks Java the stack up all the way
69. What I’m looking forward to? • Feedback from Java developers • Is Infra-as-Code with Java interesting to you? • Do you want Pulumi-LocalStack for Java productization? • Any other feedback on dev tools :)
70. References • Main Demo: github.com/oleg-nenashev/mocks-as-code-demo • This presentation: speakerdeck.com/onenashev/ workshop-mocks-as-code-in-cfg-mgmt
71. Keep Learning Tools 71 * AKA: Burning Out 101
73. It’s [always] a great time to contribute! testcontainers.org/contributing wiremock.org/participate 73
74. GitHub: oleg-nenashev Twitter: @oleg_nenashev Questions? 74