Contributing to Snappy Testing with Checkbox


To support the release of devices running snappy Ubuntu Core, Canonical has produced versions of Checkbox tailored specifically for these systems.

This document aims to provide the reader with enough information to contribute new tests, or modify existing tests, with the goal of increasing coverage wherever possible.

Brief anatomy of a Checkbox test tool

Checkbox test tools consist of a number components falling into three categories:

  • Core testing framework (known as Plainbox)
  • UI and launchers
  • Test definitions and associated data contained in a “Provider”

To add tests one need only know the specifics of the Provider(s) that form their test tool. The rest of this document will focus on Checkbox Providers and how to work on them.

Snappy Provider

The Provider housing the majority of tests for snappy Ubuntu Core systems is known as plainbox-provider-snappy and can be found in this launchpad project:

All the code both for the core of Checkbox itself and for the tests is also hosted on Launchpad. Refer to the instructions on the Code subpage to retrieve the source files for the provider:

Directory structure of the Provider

Using git to clone the provider, described above, will result in a directory that looks like this (at time of writing):

checkbox@xenial:~$ ls -1 plainbox-provider-snappy/

The first directory listed is the provider holding the tests, the second is a supporting provider which gathers information about the system at the start of a test run. Lets look in more detail at the test provider:

checkbox@xenial:~$ ls -1 plainbox-provider-snappy/plainbox-provider-snappy
bin Executable scripts that can be called as part of the test (refer to command field below)
data Data to support the running of tests e.g. configuration files Provider management script. Must be present in each provider to specify unique identifiers.
po Translation support, files here are used to provide translations for tests fields in to other languages.
src Source files and accompanying build scripts e.g. C source code and a Makefile, that are compiled in to binaries and packaged with the provider for use as part of the test (refer to command field below)
units “Job” definition files


A Job is Checkbox parlance for an individual test. They are defined in text files whose syntax is loosely based on RFC 822. Here is an example from plainbox-provider-snappy:

id: cpu/offlining_test
 Test offlining of each CPU core
 Attempts to offline each core in a multicore system.
plugin: shell
command: cpu_offlining
category_id: cpu
estimated_duration: 1s
user: root

An overview of the fields in this example test:

id A unique identifier for the job
summary A human readable name for the job. It must be one line long, ideally it should be short (50-70 characters max)

Best thought of as describing the “type” of job. Note that it is preferred for jobs to automated wherever possible so as to minimize both time to complete and possibility for operator error. The key job types starting with the most automated are:

  • shell - Run the command field and use the return value to determine the test result
  • user-interact - Ask the user to perform an action and then run the command field and use the return value to determine the test result
  • user-interact-verify - Ask the user to perform an action, then run the command field, and then ask the user to determine the test result .g. by examining the command output or observing some physical behaviour
  • manual - The last resort, just asks the user to both carry out some action(s) and then determine the test result
command A command or script to run as part of the test. A multi-line command or shell script can be used. Refer to the plugin field above for significance to the test outcome.
category_id Groups tests together for convenience in UIs etc.
estimated_duration An estimate of the time taken to execute the job. Uses hours(h), minutes(m) and seconds(s) format e.g. 1h 23m 4s

Further reading:

Test plans

Test Plans are a facility for describing a sequence of Job definitions that should be executed together. Jobs definitions are selected for inclusion in a Test Plan by either listing their identifier (see id: field above) or by inclusion of a regular expression that matches their identifier.

Here is an example of a Test Plan from plainbox-provider-snappy, it has been abbreviated:

id: snappy-generic
unit: test plan
_name: QA tests for Snappy Ubuntu Core devices
estimated_duration: 1h
id A unique identifier for the test plan
unit Distinguishes this definition from that of e.g. a test
_name A human readable name for the test plan
estimated_duration A estimate of the time taken to execute the test plan. Uses hours(h), minutes(m) and seconds(s) format e.g. 1h 23m 4s
include _id The list of tests that make up the test plan. It can be multi-line and include individual job identifiers or patterns matching multiple identifiers

Further reading:

Creating a test in five easy steps

1. Configure your development environment

Development of Checkbox tests is best carried out on an Ubuntu Desktop system. You will need either a dedicated PC or Virtual Machine running Ubuntu Desktop 16.04 (Xenial Xerus) to gain access to the tools supporting the building of packages for snappy Ubuntu Core.

When your system is up and running make sure the following packages are installed:

$ sudo apt install snapcraft git:

And to ease development, remove these pre-installed providers:

$ sudo apt remove plainbox-provider-checkbox plainbox-provider-resource-generic

    You should now have all the tools required to modify and build a provider.

2. Get the source

Clone the providers:

$ git clone

Clone the snapcraft packaging branch:

$ git clone

Further instructions will assume these were cloned in to your user’s home directory.

3. Make your changes

The units folder contains a number of files named after categories. This is not a requirement, but has been used here too make finding tests a bit easier. Either create a new file or edit an existing category.:

$ git checkout -b <NEW-BRANCH>
$ touch ~/plainbox-provider-snappy/plainbox-provider-snappy/units/<category>.pxu
$ editor ~/plainbox-provider-snappy/plainbox-provider-snappy/units/<category>.pxu

If adding a new test, make sure to add the test id to the “includes” section of any test plans you’d like this test to be part of.

4. Check your test is valid

Use the provider management script to check the provider is still valid after your modifications:

$ cd ~/plainbox-provider-snappy/plainbox-provider-snappy-resource
$ ./ develop
$ cd ~/plainbox-provider-snappy/plainbox-provider-snappy
$ ./ validate

The validate tool will provide advisories to indicate places where you provider does not follow best practices, warnings to indicate places where runtime issues could arise, and errors to indicate things which must be fixed for the provider to be parsed and run correctly by Checkbox. This validation result is given in the last line:

The provider seems to be valid

5. Build the Checkbox snap package

The tools to build a new version of the Checkbox tool snap package are found in your clone of the packaging branch. This uses the snapcraft tool which is controlled by the snapcraft.yaml file. To build a snap with your local changes examine this file for the source sections of the provider parts:

$ editor ~/packaging/snapcraft.yaml

        after: [checkbox]

Modify these so the point to your local providers:[a][b]:

        source: <path-to-local-provider>
        source-type: local
        after: [checkbox]

Then you can build the snap package:

$ snapcraft clean
$ snapcraft
Snapped checkbox-snappy_0.10~s16_amd64.snap

6. Run the tests

See Running Checkbox on Ubuntu Core which describes the process of installing and running the snap.

7. Submit your modifications to the project

To push code, report bugs etc. you will require a launchpad account:

Once you have an account you will be able to push code up to Launchpad. You can they request a merge in to the master repository. To get the code to Launchpad follow these steps:

$ git add <file>
$ git commit -m “Adds a test for...”
$ git remote add my-repo git+ssh://<USERNAME>/plainbox-provider-snappy
$ git push my-repo <NEW-BRANCH>

If you navigate to the plainbox-provider-snappy project on launchpad you should now see your repository listed under the “Other repositories” section. Here you can see my (jocave) personal repository listed at the top:


Clicking on your repository will take you to an overview page listing all your branches:


Click on the branch you have uploaded and there will be an option to “Propose for merging”.


Select this and fill out the form as follows:


Members of the team that maintain the project will be alerted to the Merge Request and will review it for landing.