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TestContainers Integration testing without the hassle Sergei @bsideup Egorov

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Integration testing Why it matters?

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Verify how your software product will behave in real-world conditions

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Isolated from other system components to avoid false negatives

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Real: databases, file systems, network interfaces, …

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Grey box testing - we know some inner details, but mostly use public APIs

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Unit testing • Simulation tests are green, yay! • Everything is mocked • DB is written by others, why should I test it?

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Integration testing https://commons.wikimedia.org/wiki/File:Cd4007.jpg • Jeez, how did it passed the Unit testing? • Is it a smoke? @#$%! YES IT IS! • Who knew that 100w soldering gun was a bit too powerful for it?

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System testing https://commons.wikimedia.org/wiki/File:UART_8250_Microchip.jpg • Takes a lot of time to solder • “Oh no, the power bus is too far away from my microchip!” • Interference between the components

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Production

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Integration testing Real-world, but isolated testing Spot the issues before the real environment Can be run during the development You have to start real databases Should be cross-platform Slower than Unit testing Pros Cons

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Obvious solution

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Abstraction layer

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CI friendly

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Cross-platform

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Docker Compose FTW! redis:
 image: redis
 ports:
 - "6379:6379"
 postgres:
 image: postgres
 ports:
 - "5432:5432"
 elasticsearch:
 image: elasticsearch:5.0.0
 ports:
 - "9200:9200"


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But…

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No ports randomization redis:
 image: redis
 ports:
 - "6379:6379"
 postgres:
 image: postgres
 ports:
 - "5432:5432"
 elasticsearch:
 image: elasticsearch:5.0.0
 ports:
 - "9200:9200"


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Fighting with Docker environment

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There is no place like

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There is no place like Except Docker Machine

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Can we improve that?

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Remove the database

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Remove the database

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As simple as PostgreSQLContainer postgresql = new PostgreSQLContainer()
 
 GenericContainer redis = new GenericContainer("redis:3")
 .withExposedPorts(6379)

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TestContainers • https://github.com/testcontainers/testcontainers-java • OSS project by Richard North, supported by ZeroTurnaround • Declarative Docker Java API wrapper • JUnit rules, can be used with other frameworks like TestNG, Cucumber, etc…

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How it works • Wraps https://github.com/docker-java/docker-java • Docker environment discovery • Will start docker-machine if it’s not started yet • Docker for Mac support • Containers cleanup on JVM shutdown

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Use case #1: testing of microservices • REST service • Java, Spring Boot • Redis and PostgreSQL • Calls some other micro-services

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Demo

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Use case #2: Docker as Selenium driver • Selenium/Selenide tests • No need to install Chrome/Firefox/etc • CI friendly

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Demo

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Use case #3: Java agent testing • Test different Java versions • Simplify I/O testing • The actual reason why ZeroTurnaround decided to use TestContainers :)

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Demo