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Oleg Nenashev
CNCF Ambassador
Modeling AWS service providers
with Testcontainers, WireMock
and Localstack
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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
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Today at
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Localstack
1. If Needed: Tools Overviews and
Integration Testing
2. Mocking and Modeling AWS services in
integration tests
3. DYI developer environments with Spring
Boot Dev Services
4. Infrastructure as Code (IaC) & Pulumi
5. Testing IaC locally & autotests
6. Advanced Troubleshooting
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Async Q&A: Testcontainers Slack, WireMock Slack
speakerdeck.com/onenashev
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> whoami
@oleg_nenashev
oleg-nenashev
Dr. Nenashev / Mr. Jenkins
Developer Tools Hacker
Community Builder
DevRel Consultant
#RussiansAgainstPutin #StandWithUkraine
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Tell your story at KCD Suisse Romande!
04-05 December 2025 - kcd.cloud-native-romandy.ch
CFP opens on July 1st
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Staging & QA
Tests
Build
Integration tests Build
Tests
Gaining confidence in you software
“Shift Left”
with modern
tools
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About You
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“Shift Left”, they said?
YAML, they gave?
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Our Repository
github.com/oleg-nenashev/workshop-aws-mocks-as-code
git clone it
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Workshop Prerequisites
● Java 21 & your favorite IDE
● Testcontainers-compatible Docker environment
○ Tested on: Docker Desktop
○ You can (try?) use: Podman, Colima, Rancher Desktop (list)
○ OR: Testcontainers Cloud
● Pulumi CLI + registration
○ Guide: www.pulumi.com/docs/install/
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Do you `make it`?
IT - Integration Tests
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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
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https://martinfowler.com/articles/
mocksArentStubs.html
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Localstack
www.localstack.cloud
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LocalStack
● Local AWS Services emulation OR mocking
● “awslocal” CLI utility
● SDKs for languages and test frameworks
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docs.localstack.cloud
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x.com/dastbe/status/1303858170155081728
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Some of Them
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● Emulated: S3, SQS, …
● Mocked: EC2 (in the FOSS lib)
● Thoughts & Prayers:
AWS GreenShift ;)
● …
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Demo
github.com/oleg-nenashev/workshop-aws-mocks-as-code/tree/main/3
_localstack-application
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SDKs
testcontainers.org … and
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LOCAL STACK
LocalStack Module
K3s Module
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Our Application
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AWS S3
SQS
External API
Our Application
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Spring Boot
and Dev Services
hdocs.spring.io/spring-boot/reference/features/dev-services.html
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See: Presentation by Moritz Halbritter
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https://www.youtube.com/watch?v=Yqss7tYP890
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Demo Time
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https://github.com/oleg-nenashev/workshop-aws-
mocks-as-code/tree/main/2_api-mocking
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1. Add Testcontainers Test
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https://github.com/oleg-nenashev/mocks-as-code-demo/blob/main/1_application/src/test/
java/com/testcontainers/demo/MessageListenerTest.java
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2. Init Localstack containers
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https://github.com/oleg-nenashev/mocks-as-code-demo/blob/main/1_application/src/test/
java/com/testcontainers/demo/MessageListenerTest.java
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3. Configure the app to use the Mock service
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https://github.com/oleg-nenashev/mocks-as-code-demo/blob/main/1_application/src/test/
java/com/testcontainers/demo/MessageListenerTest.java
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4. Write your first test!
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No Implementation?
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Fake it until you “$ make it”
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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
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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
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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
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WireMock Ecosystem & Features
wiremock.org/docs
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WireMock Ecosystem
wiremock.org/docs
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WireMock Ecosystem / Java
● Java
● Kotlin
● Scala
● Groovy
● Clojure
● (?)Android
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● JUnit 4/5
● Testcontainers
● Sprint Boot
● Spring Cloud Contract
● Quarkus
● Maven
● Spock
● Pact
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Standalone WireMock in Java
wiremock.org/docs/stubbing
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WireMock has an official Testcontainers module!
testcontainers.com/modules/wiremock
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Example
- JUnit 5
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Demo Time
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github.com/oleg-nenashev/mocks-as-code-demo
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Infrastructure-as-Code, for real
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And more constructive!
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HOWTO:
JavaDev-Ops
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Enter -as-Code Tools!
● Infrastructure as Real Code
● SDKs for programming languages
● Standard IDEs
● Standard Developer Tools
● Extensibility via libraries
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● Open-Ecosystem Tool for Infra-as-Code
● Open Source SDKs
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● Multiple destinations
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www.pulumi.com
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● 120+ extensions: www.pulumi.com/registry/
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www.pulumi.com
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Pulumi for Java
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pulumi.com/docs/languages-sdks/java/
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build.gradle
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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
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Localstack
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Pulumi Local
● github.com/localstack/pulumi-local
● Setting the environment and the
configuration right
● Just a script
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Localstack
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Hacking Time!
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github.com/oleg-nenashev/mocks-as-code-demo/
tree/main/3_deployment
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Read More
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● github.com/localstack-samples/samp
le-gradle-pulumi-testcontainers/blo
b/main/README.md by Nancy
Chauhan and Anca Ghenade
Localstack
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Pulumi for AWS or AWS Native?
● AWS Native configuration is not applied for endpoints
● APIs are slightly different in the package
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When it Goes
wrong
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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
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Deployment Pipelines and Health Checks
● There are tools for that, too!
● Testcontainers modules for k3s and KIND
● You can deploy your CI/CD tools there
● Modern Java tools have wrappers, too
○ E.g. Quarkus - docs.quarkiverse.io/quarkus-helm/dev/example-argocd
● Health checks via OTel, AWS CloudWatch or CloudTrail
○ CloudWatch is a free LocalStack plan, CloudTrail is not
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References
● Main Demo: github.com/oleg-nenashev/mocks-as-code-demo
● This and other presentations: speakerdeck.com/onenashev/
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Keep Learning Tools
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* AKA: Burning Out 101
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It’s [always] a great time to contribute!
testcontainers.org/contributing
wiremock.org/participate
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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?
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Credits
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● Siva Prasad Reddy and Oleg Shelajev, Docker / ex AtomicJar
● Nancy Chauhan and Anca Ghenade, ex LocalStack
● The demos are based on:
○ github.com/testcontainers/tc-guide-testing-aws-service-integrations-using-loca
lstack
○ github.com/testcontainers-community/testcontainers-wiremock-demo
○ github.com/oleg-nenashev/spring_io_2025-Testcontainers-workshop
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GitHub: oleg-nenashev
Twitter: @oleg_nenashev
Thank you!
Any questions?
Testcontainers Slack
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