pytest-docker-compose

This package contains a pytest plugin for integrating Docker Compose into your automated integration tests.

Given a path to a docker-compose.yml file, it will automatically build the project at the start of the test run, bring the containers up before each test starts, and tear them down after each test ends.

Dependencies

Make sure you have Docker installed.

This plugin has been tested against the following software:

• Python 3.6 and 3.5.
• pytest 3.5 and 3.4.

Note

This plugin is not compatible with Python 2.

Installation

Install the plugin using pip:

> pip install pytest-docker-compose

Usage

For performance reasons, the plugin is not enabled by default, so you must activate it manually in the tests that use it:

pytest_plugins = ["docker_compose"]

See Installing and Using Plugins for more information.

To interact with Docker containers in your tests, use the following fixtures:

docker_network_info

A list of pytest_docker_compose.NetworkInfo objects for each container, grouped by service name.

This information can be used to configure API clients and other objects that will connect to services exposed by the Docker containers in your tests.

NetworkInfo is a container with the following fields:

• container_port: The port (and usually also protocol name) exposed internally to the container. You can use this value to find the correct port for your test, when the container exposes multiple ports.
• hostname: The hostname (usually "localhost") to use when connecting to the service from the host.
• host_port: The port number to use when connecting to the service from the host.

Tip

Unless you need to interface directly with Docker primitives, this is the correct fixture to use in your tests.

docker_containers

A list of the Docker compose.container.Container objects running during the test.

docker_project

The compose.project.Project object that the containers are built from. This fixture is generally only used internally by the plugin.

Fixture Scope

The docker_network_info and docker_containers fixtures use "function" scope, meaning that all of the containers are torn down after each individual test.

This is done so that every test gets to run in a "clean" environment.

However, this can potentially make a test suite take a very long time to complete, so you can declare you own versions of the fixtures with a different scope if desired.

Here is an example of creating a fixture that will keep all of the containers running throughout the entire test session:

import pytest
from pytest_docker_compose import DockerComposePlugin

@pytest.fixture(scope="session")
def session_containers(docker_project):
  containers = DockerComposePlugin._containers_up(docker_project)
  yield containers
  DockerComposePlugin._containers_down(docker_project, containers)

@pytest.fixture(scope="session")
def session_network_info(session_containers):
  return DockerComposePlugin._extract_network_info(session_containers)

Caution!

Take extra care to ensure that residual data/configuration/files/etc. are cleaned up on all of the containers after each test!

!DANGER!

This functionality has not been tested extensively, and you may run into strange and/or difficult-to-isolate issues that are unique to your environment/configuration/etc.

It is strongly recommended that you investigate alternative approaches to improving test performance, for example by using pytest-xdist to run tests in parallel.

Waiting for Services to Come Online

The fixture will wait until every container is up before handing control over to the test.

However, just because a container is up does not mean that the services running on it are ready to accept incoming requests yet!

If your tests need to wait for a particular condition (for example, to wait for an HTTP health check endpoint to send back a 200 response), make sure that your fixtures account for this.

Here's a simple example of a fixture that waits for an HTTP service to come online before starting each test.

import pytest
import typing
from pytest_docker_compose import NetworkInfo
from time import sleep, time

from my_app import ApiClient

pytest_plugins = ["docker_compose"]


@pytest.fixture(name="api_client")
def fixture_api_client(
        docker_network_info: typing.Dict[str, typing.List[NetworkInfo]],
) -> ApiClient:
    # ``docker_network_info`` is grouped by service name.
    service = docker_network_info["my_api_service"][0]

    # Create an instance of our custom application's API client.
    api_client = ApiClient(
        base_url=f"http://{service.hostname}:{service.host_port}/api/v1",
    )

    # Wait for the HTTP service to be ready.
    start = time()
    timeout = 5

    for name, network_info in docker_network_info.items():
        while True:
            if time() - start >= timeout:
                raise RuntimeError(
                    f"Unable to start all container services "
                    "within {timeout} seconds.",
                )

            try:
                if api_client.health_check()["status"] == "ok":
                    break
            except (ConnectionError, KeyError):
                pass

            sleep(0.1)

    # HTTP service is up and listening for requests.
    return api_client


# Tests can then interact with the API client directly.
def test_frog_blast_the_vent_core(api_client: ApiClient):
    assert api_client.frog_blast_the_vent_core() == {
        "status": "I'm out of ammo!",
    }

Running Integration Tests

Use pytest to run your tests as normal:

pytest

By default, this will look for a docker-compose.yml file in the current working directory. You can specify a different file via the --docker-compose option:

pytest --docker-compose=/path/to/docker-compose.yml

Tip

Alternatively, you can specify this option in your pytest.ini file:

[pytest]
addopts = --docker-compose=/path/to/docker-compose.yml

The option will be ignored for tests that do not use this plugin.

See Configuration Options for more information on using configuration files to modify pytest behavior.