Fake it until you make it. ITs with WireMock, Testcontainers and Quarkus

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Oleg Nenashev @oleg_nenashev Fake it until you `make it` API Integration testing with Testcontainers, WireMock and Quarkus IET Summit, 27 January 2025

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> whoami @oleg_nenashev oleg-nenashev Dr. Nenashev / Mr. Jenkins Community Builder Developer Tools Hacker Independent Consultant #RussiansAgainstPutin #StandWithUkraine

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rts.ch/info/regions/neuchatel/12836885-la-population-neuchateloise-en-hausse-malgre-un-recul-dans-les-montagnes.html

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Async Q&A: Testcontainers and WireMock Slack speakerdeck.com/onenashev

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About You 6

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When IT Goes wrong 7

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Do you `make it`? IT - Integration Tests 10

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Integration Testing 12 ● Multiple technology stacks and toolchains ● Many teams involved ● Sacred knowledge ● [Almost] always too late

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APIs are the Key for Developer Productivity response request Client App Server HTTP/2 Storage response request API API

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API specs API tech

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18 Staging & QA Tests Build Integration tests Build Tests Gaining conﬁdence in you software “Shift Left” with modern tools

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19 https://martinfowler.com/articles/ mocksArentStubs.html

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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) 4. Mocking at the code level Slow Fast Nope Accu- rate * For Testcontainers, see the slides

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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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Example - Java 23

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https://testcontainers.com/modules/

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25 LOCAL STACK https://testcontainers.com/modules/

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26 SDKs testcontainers.org … and

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27 github.com/testcontainers/ testcontainers-go

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Demo Time 28 github.com/oleg-nenashev/mocks-as-code-demo/ tree/main/1_application

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No Implementation? 29 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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API Mocking for Java. Examples en.wikipedia.org/wiki/Comparison_of_API_simulation_tools Proprietary Open Source `

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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.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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WireMock Ecosystem & Features wiremock.org/docs

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WireMock Ecosystem wiremock.org/docs

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WireMock in Java wiremock.org/docs/stubbing * Gradle® and the Gradlephant logo are registered trademarks of Gradle, Inc.

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WireMock Ecosystem / Java ● Java ● Kotlin ● Scala ● Groovy ● Clojure ● (?)Android 38 ● JUnit 4/5 ● Testcontainers ● Sprint Boot ● Spring Cloud Contract ● Quarkus ● Maven / Gradle Build Tool ● Spock ● Pact * Gradle® 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

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Example - JUnit 5 39

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40 WireMock has an official Testcontainers module! testcontainers.com/modules/wiremock

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WireMock as a Proxy Tests API Provider ● Fault injection ● Recording ● Protocol Verification

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42 DEMO TIME https://github.com/wiremock/wiremock-docker

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WireMock or Testcontainers?

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Choosing a right tool * ● Need database or complex dynamic environment? ○ YES => Testcontainers ● Do you have a ready implementation? ○ NO => WireMock/Microcks ● Is it containerized and lightweight? ○ NO => WireMock/Microcks ● Can you easily trigger the desired scenarios? ○ NO => WireMock/Microcks ● Else: => Testcontainers 44 * Your mileage may vary ** More later *** I just like footnotes * Likely, you want to use both

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46 WireMock has an official Testcontainers module! testcontainers.com/modules/wiremock

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Proxy can be made transparent in your test! 47 Tests

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WireMock Proxy? Why? ● Record & Playback for Request sequences ● Reverse engineering of legacy undocumented APIs ● NEW: OpenAPI Standard Compliance Veriﬁcation (in 3.0 Beta) ● Emulating complex cases ○ Overriding particular responses ○ Emulating response sequences / Stateful behavior ○ Failure Injection 48

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Quarkus or Spring What do you use ?

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If you like / use You can do [almost] the same as below Devoxx BE Video with Oleg Shelajev: youtube.com/watch?v=eFILbyaMI2A Our demo: github.com/testcontainers-community/ testcontainers-wiremock-demo 50 TL;DR: Two Olegs

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Source: https://www.codelikethewind.org/2022/05/03/3-reasons- why-all-java-developers-should-consider-quarkus/ ● Reference implementation of new Java Developer Experience ● Spring Boot is catching up ● Micronaut & Co are great, too

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Quarkus Dev Services ● Automatic provisioning of unconﬁgured services in development and test mode ● Transparent to your application ● Mostly containerized, with Testcontainers 52 https://quarkus.io/guides/dev-services

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Dev Services ● Mostly containerized, with Testcontainers 53 Presentation by Daniel Oh: https://www.youtube.com/watch?v=moIFTj9KW1c

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55 docs.quarkiverse.io/quarkus-wiremock/dev/index.html

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@QuarkusTest or @QuarkusIntegrationTest

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And a Quarkus Dev Service! docs.quarkiverse.io/quarkus-wiremock/dev/index.html

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docs.quarkiverse.io/qu arkus-wiremock/dev/in dex.html#extension-co nfiguration-reference

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59 DEMO TIME https://github.com/oleg-nenashev/gradle-quarkus-plugin-demo

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More Demos ● Simple WireMock and Testcontainers demo: github.com/testcontainers-community/testcontainers-wiremock-demo ● WireMock and Docker integration tests: https://github.com/wiremock/wiremock-docker ● Quarkus Dev Service for WireMock and Testcontainers: https://github.com/oleg-nenashev/gradle-quarkus-plugin-demo ● Spring Boot + Testcontainers and WireMock + LocalStack: https://github.com/oleg-nenashev/mocks-as-code-demo

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Lessons Learned 62

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Takeaways 63 ● Shift left the integration testing ● API Mocking / abstraction are great… when used right ● There is no silver bullet ● WireMock and Testcontainers address their own use-cases ● They work well together!

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Choosing a right tool * ● Need database or complex dynamic environment? ○ YES => Testcontainers ● Do you have a ready implementation? ○ NO => WireMock/Microcks ● Is it containerized and lightweight? ○ NO => WireMock/Microcks ● Can you easily trigger the desired scenarios? ○ NO => WireMock/Microcks ● Else: => Testcontainers 64 * Your mileage may vary ** More later *** I just like footnotes * Likely, you want to use both

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Keep Learning Tools 65 * AKA: Burning Out 101

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It’s [always] a great time to contribute! testcontainers.org/contributing wiremock.org/participate 67

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GitHub: oleg-nenashev Twitter: @oleg_nenashev WireMock Slack Questions? Testcontainers Slack 68

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Credits 69 ● All WireMock, Testcontainers and Quarkus contributors ● Siva Prasad Reddy, JetBrains and Oleg Shelajev, Docker ● All FOSS folks