test_containers_46x.md

id	title	sidebar_label	slug
test_containers_46	Testcontainers	Testcontainers	test_containers_46.html

Testcontainers

The Testcontainers project provides lightweight, ephemeral instances of common databases, elasticsearch, kafka, Selenium web browsers, or anything else that can run in a Docker container, ideal for use inside tests.

This module provides integration for using Testcontainers with kotest. To use add the below dependency to your Gradle build file.

io.kotest.extensions:kotest-extensions-testcontainers:${kotest.version}

Note: The group id is different (io.kotest.extensions) from the main kotest dependencies (io.kotest).

For Maven, you will need these dependencies:

<dependency>
    <groupId>io.kotest.extensions</groupId>
    <artifactId>kotest-extensions-testcontainers</artifactId>
    <version>${kotest.version}</version>
    <scope>test</scope>
</dependency>

Having these dependencies in test classpath will bring extension methods into scope which let you convert any Startable such as a DockerContainer into a kotest TestListener, which you can register with Kotest and then Kotest will manage lifecycle of container for you.

For example:

import io.kotest.core.spec.style.FunSpec
import io.kotest.extensions.testcontainers.perTest
import org.testcontainers.containers.GenericContainer

class DatabaseRepositoryTest : FunSpec({
   val redisContainer = GenericContainer<Nothing>("redis:5.0.3-alpine")
   listener(redisContainer.perTest()) //converts container to listener and registering it with Kotest.

   test("some test which assume to have redis container running") {
      //
   }
})

In above example, the perTest() extension method converts the container into a TestListener, which starts the redis container before each test and stops it after test. Similarly if you want to reuse the container for all tests in a single spec class you can use perSpec() extension method, which converts the container into a TestListener which starts the container before running any test in the spec, and stops it after all tests, thus a single container is used by all tests in spec class.