A presentation at DevXConf by Oleg Šelajev
How to make a world-class integration testing library?
testcontainers.org
Oleg Šelajev Developer relations @shelajev github.com/shelajev oleg@atomicjar.com
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e2e Integration tests Unit tests By Unknown author - U.S. Army Photo, Public Domain, https://commons.wikimedia.org/w/index.php?curid=55124
https://labs.spotify.com/2018/01/11/testing-of-microservices/
Is this the goal?
You’re given tools but they don’t work reliably or are di cult to use to solve problems, you don’t know exist ffi fi slow, joyless, or signi cantly behind the state of the art
—version: ‘2’ services: zookeeper: image: con uentinc/cp-zookeeper:7.0.1 ports: - “32181:32181” environment: ZOOKEEPER_CLIENT_PORT: 32181 ZOOKEEPER_TICK_TIME: 2000 kafka: image: con uentinc/cp-kafka:7.0.1 ports: - “29092:29092” depends_on: - zookeeper environment: KAFKA_BROKER_ID: 1 KAFKA_ZOOKEEPER_CONNECT: zookeeper:32181 KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://localhost:29092 fl fl KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR :1
What does winning look like?
Replacing a hard problem with a hard solution is not success. Nor is replacing an easy problem with an easy solution.
Reliability
Trustworthyness Shifting failures left Errors making sense Sensible defaults Developers are people too!
System checks Checking the system… ✔ Docker version should be at least 1.6.0 ✔ Docker environment should have more than 2GB free disk space ✔ File should be mountable ℹ︎ ✔ A port exposed by a docker container should be accessible
During After
The problem Extra mile Port conflicts Port randomization Hard-coded scenarios Data-driven tests Slow tests Parallelization
Technology radar We think it’s a useful default option for creating a reliable environment for running tests. … Our teams have consistently found this library of programmable, lightweight and disposable containers to make functional tests more reliable. https://www.thoughtworks.com/en-us/radar/languages-and-frameworks/testcontainers
The simplest way JDBC driver magic: spring.datasource.url=jdbc:tc:postgresql:14-alpine: testcontainers/database With a schema initialization: jdbc:tc:mysql:5.7.34: init_mysql.sql databasename?TC_INITSCRIPT=file:src/main/resources/ With additional con g: / databasename?TC_TMPFS=/testtmpfs:rw / / / / / / / fi jdbc:tc:postgresql:9.6.8:
The ecosystem of modules KafkaContainer kafka = new KafkaContainer( DockerImageName.parse(“confluentinc/cp-kafka”).withTag(“5.4.3”) ) public ToxiproxyContainer toxiproxy = new ToxiproxyContainer(DockerImageName.parse(“shopify/toxiproxy:2.1.0”)) .withNetwork(network) .withNetworkAliases(“toxiproxy”); PostgreSQLContainer<?> postgreSQLContainer = new PostgreSQLContainer (DockerImageName.parse(“postgresql:14-alpine”));
< K3sContainer k3s = new K3sContainer( DockerImageName.parse(“rancher/k3s:v1.21.3-k3s1”)) .withLogConsumer(new Slf4jLogConsumer(log));
testcontainers.org
Developer Experience Community Technical excellence
The generic API
< GenericContainer<?> redis = new GenericContainer (“redis:6-alpine”) .withExposedPorts(6379);
The generic API
If it’s not in the docs — it doesn’t exist!
The problem with docs (a) people will never read external docs; (b) people will rarely read inline docs/help strings/tooltips; (c) people will most likely only read the information that is shown to them
The IDE is your only friend!
Our clients’ clients love us
Private registries Local API: final PostgreSQLContainer<?> mysql = new PostgreSQLContainer ( DockerImageName.parse(“registry.mycompany.com/mirror/mysql:8.0.24”) .asCompatibleSubstituteFor(“mysql”) ); Con guration: TESTCONTAINERS_HUB_IMAGE_NAME_PREFIX=registry.mycompany.com/mirror/ Programmatic API:
< fi public abstract class ImageNameSubstitutor implements Function<DockerImageName, DockerImageName>
Chaos engineering public Network network = Network.newNetwork();
< public GenericContainer<?> redis = new GenericContainer (DockerImageName.parse(“redis:6-alpine”)) .withExposedPorts(6379) .withNetwork(network);
Chaos engineering public Network network = Network.newNetwork(); public GenericContainer<?> redis = new GenericContainer (DockerImageName.parse(“redis:6-alpine”)) .withExposedPorts(6379) .withNetwork(network);
< public ToxiproxyContainer toxiproxy = new ToxiproxyContainer(DockerImageName.parse(“shopify/toxiproxy:2.1.0”)) .withNetwork(network) .withNetworkAliases(“toxiproxy”);
Chaos engineering final ToxiproxyContainer.ContainerProxy proxy = toxiproxy.getProxy(redis, 6379); proxy.toxics() .latency(“latency”, ToxicDirection.DOWNSTREAM, 1_100) .setJitter(100); • • • • • • bandwidth - Limit a connection to a maximum number of kilobytes per second. latency - Add a delay to all data going through the proxy. The delay is equal to latency +/- jitter. slicer - Slices TCP data up into small bits, optionally adding a delay between each sliced “packet”. slowClose - Delay the TCP socket from closing until delay milliseconds has elapsed. timeout - Stops all data from getting through, and closes the connection after timeout limitData - Closes connection when transmitted data exceeded limit.
Reusable containers Extending the lifecycle of the containers Local API: static KafkaContainer kafka = new KafkaContainer() .withReuse(true); fi Con guration:
Changing local development git clone https://github.com/shelajev/ primes-kafka.git && cd primes-kafka ./mvnw quarkus:dev Clone & Run!
Excellent developer experience is a careful balance between boredom and anxiety. Ideally, it would make solving simple problems trivial, complex ones simple, and have enough flexibility to inspire hope for tackling the impossible ones!
In this session, we’d like to share the story of Testcontainers - the world’s most popular integration testing libraries. And look at the developer experience choices that led libraries aimed at a tedious and often ungrateful task of environment setup and integration testing to bring joy and even influence how developers approach their projects altogether.
The following resources were mentioned during the presentation or are useful additional information.
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