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Launch a docker instance around test runs

Project description

A tox plugin which runs one or more Docker containers during the test run.

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Usage and Installation

tox loads all plugins automatically. It is recommended that you install the tox-docker plugin into the same Python environment as you install tox into, whether that’s a virtualenv, etc.

You do not need to do anything special when running tox to invoke tox-docker. You do need to configure your project to request docker instances (see “Configuration” below).


In the testenv section, list the Docker images you want to include in the docker multi-line-list. Be sure to include the version tag.

You can include environment variables to be passed to the docker container via the dockerenv multi-line list. These will also be made available to your test suite as it runs, as ordinary environment variables:

docker =
dockerenv =

Host and Port Mapping

By default, tox-docker runs the container with the “publish all ports” option. You may also specify port publishing in tox.ini, in a new section like:

ports = 5432:5432/tcp

The image name – everything after the docker: in the section header – must exactly match the image name used in your testenv’s docker setting. Published ports are separated by a newline and are in the format <HOST>:<CONTAINER>/<PROTOCOL>.

Any port the container exposes will be made available to your test suite via environment variables of the form <image-basename>_<exposed-port>_<protocol>_PORT. For instance, for the PostgreSQL container, there will be an environment variable POSTGRES_5432_TCP_PORT whose value is the ephemeral port number that docker has bound the container’s port 5432 to.

Likewise, exposed UDP ports will have environment variables like TELEGRAF_8092_UDP_PORT Since it’s not possible to check whether UDP port is open it’s just mapping to environment variable without any checks that service up and running.

The host name for each service is also exposed via environment as <image-basename>_HOST, which is POSTGRES_HOST and TELEGRAF_HOST for the two examples above.

Deprecation Note: In older versions of tox-docker, the port was exposed as <image-basename>-<exposed-port>-<protocol>. This additional environment variable is deprecated, but will be supported until tox-docker 2.0.

Health Checking

As of version 1.4, tox-docker uses Docker’s health checking to determine when a container is fully running, before it begins your test. For Docker images that contain a HEALTHCHECK command, tox-docker uses that.

You may also specify a custom health check in tox.ini, in a new section like:

healthcheck_cmd = redis-cli ping | grep -q PONG
healthcheck_interval = 1
healthcheck_timeout = 1
healthcheck_retries = 30
healthcheck_start_period = 0.5

The image name – everything after the docker: in the section header – must exactly match the image name used in your testenv’s docker setting.

tox-docker will print a message for each container that it is waiting on a health check from, whether via the container’s built-in HEALTHCHECK or a custom health check.

If you are running in a Docker-In-Docker environment, you can override the address used for port checking using the environment variable TOX_DOCKER_GATEWAY. This variable should be the hostname or ip address used to connect to the container.

Container Linking

Containers can be linked together using the links key. The links configuration should use the form {IMAGE_NAME} or {IMAGE_NAME}:{ALIAS}. Multiple links may be provided. If you do not provide an alias, the untagged image name will be used. The default aliases in the contrived example below would be ‘memcached’, ‘postgres’, and ‘elasticsearch’. No validation is performed on the alias. You are responsible for providing a valid identifier. If the image name produces an auto-generated alias that is invalid, you will need to provide a suitable alternative yourself using the form {IMAGE_NAME}:{ALIAS} as documented above.

For example:

docker =
dockerenv =
    ES_JAVA_OPTS=-Xms512m -Xmx512m
links = memcached
links =

Note: No dependency resolution is performed. You must define containers in proper dependency order. An error will be raised if a link references a container that has not yet been processed. Notice in the example above that postgres is listed after memcached. And elasticsearch is listed after both memcached and postgres. It would be an error to list postgres before memcached and likewise for placing elasticsearch before either postgres or memcached.

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