Docker Compose

Benefits

Similar to generic containers support, it's also possible to run a bespoke set of services specified in a docker-compose.yml file.

This is intended to be useful on projects where Docker Compose is already used in dev or other environments to define services that an application may be dependent upon.

Behind the scenes, Testcontainers actually launches a temporary Docker Compose client - in a container, of course, so it's not necessary to have it installed on all developer/test machines.

Example

A single class rule, pointing to a docker-compose.yml file, should be sufficient to launch any number of services required by your tests:

@ClassRule
public static DockerComposeContainer environment =
    new DockerComposeContainer(new File("src/test/resources/compose-test.yml"))
            .withExposedService("redis_1", REDIS_PORT)
            .withExposedService("elasticsearch_1", ELASTICSEARCH_PORT);

In this example, compose-test.yml should have content such as:

redis:
  image: redis
elasticsearch:
  image: elasticsearch

Note that it is not necessary to define ports to be exposed in the YAML file; this would inhibit reuse/inclusion of the file in other contexts.

Instead, Testcontainers will spin up a small 'ambassador' container for every exposed service port, which will proxy between the Compose-managed container and a port that's accessible to your tests. This is done using a separate, minimal container that runs HAProxy in TCP proxying mode.

Accessing a container from tests

The rule provides methods for discovering how your tests can interact with the containers:

  • getServiceHost(serviceName, servicePort) returns the IP address where the container is listening (via an ambassador container)
  • getServicePort(serviceName, servicePort) returns the Docker mapped port for a port that has been exposed (via an ambassador container)

For example, with the Redis example above, the following will allow your tests to access the Redis service:

String redisUrl = environment.getServiceHost("redis_1", REDIS_PORT)
                    + ":" +
                  environment.getServicePort("redis_1", REDIS_PORT);

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