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Contributing to machine

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Want to hack on Machine? Awesome! Here are instructions to get you started.

Machine is a part of the Docker project, and follows the same rules and principles. If you're already familiar with the way Docker does things, you'll feel right at home.

Otherwise, go read Docker's contributions guidelines.

The requirements to build Machine are:

  1. A running instance of Docker
  2. The bash shell

To build, run:

$ script/build

From the Machine repository's root. Machine will run the build inside of a Docker container and the compiled binaries will appear in the project directory on the host.

By default, Machine will run a build which cross-compiles binaries for a variety of architectures and operating systems. If you know that you are only compiling for a particular architecture and/or operating system, you can speed up compilation by overriding the default argument that the build script passes to gox. This is very useful if you want to iterate quickly on a new feature, bug fix, etc.

For instance, if you only want to compile for use on OS X with the x86_64 arch, run:

$ script/build -osarch="darwin/amd64"

If you don't need to run the docker build to generate the image on each compile, i.e. if you have built the image already, you can skip the image build using the SKIP_BUILD environment variable, for instance:

$ SKIP_BUILD=1 script/build -osarch="darwin/amd64"

If you have any questions we're in #docker-machine on Freenode.

Unit Tests

To run the unit tests for the whole project, using the following script:

$ script/test

This will run the unit tests inside of a container, so you don't have to worry about configuring your environment properly before doing so.

To run the unit tests for only a specific subdirectory of the project, you can pass an argument to that script to specify which directory, e.g.:

$ script/test ./drivers/amazonec2

If you make a pull request, it is highly encouraged that you submit tests for the code that you have added or modified in the same pull request.

Code Coverage

Machine includes a script to check for missing *_test.go files and to generate an HTML-based representation of which code is covered by tests.

To run the code coverage script, execute:

$ ./script/coverage serve

You will see the results of the code coverage check as they come in.

This will also generate the code coverage website and serve it from a container on port 8000. By default, / will show you the source files from the base directory, and you can navigate to the coverage for any particular subdirectory of the Docker Machine repo's root by going to that path. For instance, to see the coverage for the VirtualBox driver's package, browse to /drivers/virtualbox.

You can hit CTRL+C to stop the server.

Integration Tests

Setup

We utilize BATS for integration testing. This runs tests against the generated binary. To use, first make sure to install BATS. Then run ./script/build to generate the binary for your system.

Basic Usage

Once you have the binary, the integration tests can be invoked using the test/integration/run-bats.sh wrapper script.

Using this wrapper script, you can invoke a test or subset of tests for a particular driver. To set the driver, use the DRIVER environment variable.

The following examples are all shown relative to the project's root directory, but you should be able to invoke them from any directory without issue.

To invoke just one test:

$ DRIVER=virtualbox ./test/integration/run-bats.sh test/integration/core/core-commands.bats
 ✓ virtualbox: machine should not exist
 ✓ virtualbox: create
 ✓ virtualbox: ls
 ✓ virtualbox: run busybox container
 ✓ virtualbox: url
 ✓ virtualbox: ip
 ✓ virtualbox: ssh
 ✓ virtualbox: docker commands with the socket should work
 ✓ virtualbox: stop
 ✓ virtualbox: machine should show stopped after stop
 ✓ virtualbox: machine should now allow upgrade when stopped
 ✓ virtualbox: start
 ✓ virtualbox: machine should show running after start
 ✓ virtualbox: kill
 ✓ virtualbox: machine should show stopped after kill
 ✓ virtualbox: restart
 ✓ virtualbox: machine should show running after restart

17 tests, 0 failures
Cleaning up machines...
Successfully removed bats-virtualbox-test

To invoke a shared test with a different driver:

$ DRIVER=digitalocean ./test/integration/run-bats.sh test/integration/core/core-commands.bats
...

To invoke a directory of tests recursively:

$ DRIVER=virtualbox ./test/integration/run-bats.sh test/integration/core/
...

If you want to invoke a group of tests across two or more different drivers at once (e.g. every test in the drivers directory), at the time of writing there is no first-class support to do so - you will have to write your own wrapper scripts, bash loops, etc. However, in the future, this may gain first-class support as usage patterns become more clear.

Extra Create Arguments

In some cases, for instance to test the creation of a specific base OS (e.g. RHEL) as opposed to the default with the common tests, you may want to run common tests with different create arguments than you get out of the box.

Keep in mind that Machine supports environment variables for many of these flags. So, for instance, you could run the command (substituting, of course, the proper secrets):

$ DRIVER=amazonec2 \
  AWS_VPC_ID=vpc-xxxxxxx \
  AWS_SECRET_ACCESS_KEY=yyyyyyyyyyyyy \
  AWS_ACCESS_KEY_ID=zzzzzzzzzzzzzzzz \
  AWS_AMI=ami-12663b7a \
  AWS_SSH_USER=ec2-user \
  ./test/integration/run-bats.sh test/integration/core

in order to run the core tests on Red Hat Enterprise Linux on Amazon.

Layout

The test/integration directory is layed out to divide up tests based on the areas which the test. If you are uncertain where to put yours, we are happy to guide you.

At the time of writing, there is:

  1. A core directory which contains tests that are applicable to all drivers.
  2. A drivers directory which contains tests that are applicable only to specific drivers with sub-directories for each provider.
  3. A cli directory which is meant for testing functionality of the command line interface, without much regard for driver-specific details.

Guidelines

The best practices for writing integration tests on Docker Machine are still a work in progress, but here are some general guidelines from the maintainers:

  1. Ideally, each test file should have only one concern.
  2. Tests generally should not spin up more than one machine unless the test is deliberately testing something which involves multiple machines, such as an ls test which involves several machines, or a test intended to create and check some property of a Swarm cluster.
  3. BATS will print the output of commands executed during a test if the test fails. This can be useful, for instance to dump the magic $output variable that BATS provides and/or to get debugging information.
  4. It is not strictly needed to clean up the machines as part of the test. The BATS wrapper script has a hook to take care of cleaning up all created machines after each test.

Drivers

Docker Machine has several included drivers that supports provisioning hosts in various providers. If you wish to contribute a driver, we ask the following to ensure we keep the driver in a consistent and stable state:

  • Address issues filed against this driver in a timely manner
  • Review PRs for the driver
  • Be responsible for maintaining the infrastructure to run unit tests and integration tests on the new supported environment
  • Participate in a weekly driver maintainer meeting

If you can commit to those, the next step is to make sure the driver adheres to the spec.

Once you have created and tested the driver, you can open a PR.

Note: even if those are met does not guarantee a driver will be accepted. If you have questions, please do not hesitate to contact us on IRC.