Testcontainers for your Golang projects

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Oleg Nenashev, @oleg_nenashev CNCF Ambassador

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Oleg Nenashev @oleg_nenashev oleg-nenashev Community builder Developer Tools Hacker Testcontainers Champion Cloud Native Suisse Romande #RussiansAgainstPutin #StandWithUkraine

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When IT Goes wrong

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Do you `make it`? IT - Integration Tests

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

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

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Build Unit tests Publish Reports Integration tests Publish Reports NOW “Shift Left” Fast integrations tests are critical

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Ways to do integration testing 1. Testing against Production/Staging Slow Fast Nope Accu- rate 2. Testing against a simplified/containerized instance (e.g. Testcontainers) 4. Mocking at the code level (e.g. GoMock) 3. Mocking at the API provider level (e.g. Microcks, WireMock)

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SDKs testcontainers.org … and

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github.com/testcontainers/ testcontainers-go

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60+ Testcontainers Modules for Golang testcontainers.com/modules/?language=go

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

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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 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 for Go Testcontainers Module REST API Client Go test integrations go.wiremock.org github.com/wiremock/wiremock-testcontainers-go

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DEMO - API Mocking with WireMock ● Golang, Testcontainers, WireMock Module ● Sources location: github.com/wiremock/wiremock-testcontain ers-go/tree/main/examples/quickstart

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github.com/wiremock/wiremock-testcontainers-go

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Is a Single Container Enough? - asking for a container CI/CD guy

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Platforms Docker Compose

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References ● Testcontainers for Golang: https://golang.testcontainers.org/ ● WireMock Demos: github.com/wiremock/wiremock-testcontainers-go/tree/main/examples

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Takeaways 31 ● 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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It’s [always] a great time to contribute! testcontainers.org/contributing wiremock.org/participate 33

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Learn More at Oleg Nenashev - Workshop Mocks as Code. Modeling AWS service providers with Testcontainers, WireMock and Localstack LocalStack

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KCD Suisse Romande Dec 2025, Genève, CERN

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

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GitHub: oleg-nenashev Twitter: @oleg_nenashev Questions? Gradle Community Slack, #developer-productivity-engineering Testcontainers Slack