Test Development


The purpose of this page is to describe how to write integration tests for cloud-init. As a test writer you need to develop a test configuration and a verification file:

  • The test configuration specifies a specific cloud-config to be used by cloud-init and a list of arbitrary commands to capture the output of (e.g my_test.yaml)
  • The verification file runs tests on the collected output to determine the result of the test (e.g. my_test.py)

The names must match, however the extensions will of course be different, yaml vs py.


The test configuration is a YAML file such as ntp_server.yaml below:

# NTP config using specific servers (ntp_server.yaml)
cloud_config: |
      - pool.ntp.org
  ntp_installed_servers: |
    dpkg -l | grep ntp | wc -l
  ntp_conf_dist_servers: |
    ls /etc/ntp.conf.dist | wc -l
  ntp_conf_servers: |
    cat /etc/ntp.conf | grep '^server'

There are two keys, 1 required and 1 optional, in the YAML file:

  1. The required key is cloud_config. This should be a string of valid YAML that is exactly what would normally be placed in a cloud-config file, including the cloud-config header. This essentially sets up the scenario under test.
  2. The optional key is collect_scripts. This key has one or more sub-keys containing strings of arbitrary commands to execute (e.g. `cat /var/log/cloud-config-output.log`). In the example above the output of dpkg is captured, grep for ntp, and the number of lines reported. The name of the sub-key is important. The sub-key is used by the verification script to recall the output of the commands ran.

Default Collect Scripts

By default the following files will be collected for every test. There is no need to specify these items:

  • /var/log/cloud-init.log
  • /var/log/cloud-init-output.log
  • /run/cloud-init/.instance-id
  • /run/cloud-init/result.json
  • /run/cloud-init/status.json
  • `dpkg-query -W -f='${Version}' cloud-init`


The verification script is a Python file with unit tests like the one, ntp_server.py, below:

"""cloud-init Integration Test Verify Script (ntp_server.yaml)"""
from tests.cloud_tests.testcases import base

class TestNtpServers(base.CloudTestCase):
    """Test ntp module"""

    def test_ntp_installed(self):
        """Test ntp installed"""
        out = self.get_data_file('ntp_installed_servers')
        self.assertEqual(1, int(out))

    def test_ntp_dist_entries(self):
        """Test dist config file has one entry"""
        out = self.get_data_file('ntp_conf_dist_servers')
        self.assertEqual(1, int(out))

    def test_ntp_entires(self):
        """Test config entries"""
        out = self.get_data_file('ntp_conf_servers')
        self.assertIn('server pool.ntp.org iburst', out)

Here is a breakdown of the unit test file:

  • The import statement allows access to the output files.
  • The class can be named anything, but must import the base.CloudTestCase
  • There can be 1 to N number of functions with any name, however only tests starting with test_* will be executed.
  • Output from the commands can be accessed via self.get_data_file('key') where key is the sub-key of collect_scripts above.


Integration tests are located under the tests/cloud_tests directory. Test configurations are placed under configs and the test verification scripts under testcases:

cloud-init$ tree -d tests/cloud_tests/
├── configs
│   ├── bugs
│   ├── examples
│   ├── main
│   └── modules
└── testcases
    ├── bugs
    ├── examples
    ├── main
    └── modules

The sub-folders of bugs, examples, main, and modules help organize the tests. View the README.md in each to understand in more detail each directory.

Development Checklist

  • Configuration File
    • Named ‘your_test_here.yaml’
    • Contains at least a valid cloud-config
    • Optionally, commands to capture additional output
    • Valid YAML
    • Placed in the appropriate sub-folder in the configs directory
  • Verification File
    • Named ‘your_test_here.py’
    • Valid unit tests validating output collected
    • Passes pylint & pep8 checks
    • Placed in the appropriate sub-folder in the testcsaes directory
  • Tested by running the test:

    $ python3 -m tests.cloud_tests run -v -n <release of choice> \
        --deb <build of cloud-init> \
        -t tests/cloud_tests/configs/<dir>/your_test_here.yaml


Executing tests has three options:

  • run an alias to run both collect and verify
  • collect deploys on the specified platform and os, patches with the requested deb or rpm, and finally collects output of the arbitrary commands.
  • verify given a directory of test data, run the Python unit tests on it to generate results.


The first example will provide a complete end-to-end run of data collection and verification. There are additional examples below explaining how to run one or the other independently.

$ git clone https://git.launchpad.net/cloud-init
$ cd cloud-init
$ python3 -m tests.cloud_tests run -v -n trusty -n xenial \
    --deb cloud-init_0.7.8~my_patch_all.deb

The above command will do the following:

  • -v verbose output
  • run both collect output and run tests the output
  • -n trusty on the Ubuntu Trusty release
  • -n xenial on the Ubuntu Xenial release
  • --deb cloud-init_0.7.8~patch_all.deb use this deb as the version of cloud-init to run with

For a more detailed explanation of each option see below.


If developing tests it may be necessary to see if cloud-config works as expected and the correct files are pulled down. In this case only a collect can be ran by running:

$ python3 -m tests.cloud_tests collect -n xenial -d /tmp/collection \
    --deb cloud-init_0.7.8~my_patch_all.deb

The above command will run the collection tests on xenial with the provided deb and place all results into /tmp/collection.


When developing tests it is much easier to simply rerun the verify scripts without the more lengthy collect process. This can be done by running:

$ python3 -m tests.cloud_tests verify -d /tmp/collection

The above command will run the verify scripts on the data discovered in /tmp/collection.


The following outlines the process flow during a complete end-to-end LXD-backed test.

  1. Configuration
    • The back end and specific OS releases are verified as supported
    • The test or tests that need to be run are determined either by directory or by individual yaml
  2. Image Creation
    • Acquire the daily LXD image
    • Install the specified cloud-init package
    • Clean the image so that it does not appear to have been booted
    • A snapshot of the image is created and reused by all tests
  3. Configuration
    • For each test, the cloud-config is injected into a copy of the snapshot and booted
    • The framework waits for /var/lib/cloud/instance/boot-finished (up to 120 seconds)
    • All default commands are ran and output collected
    • Any commands the user specified are executed and output collected
  4. Verification
    • The default commands are checked for any failures, errors, and warnings to validate basic functionality of cloud-init completed successfully
    • The user generated unit tests are then ran validating against the collected output
  5. Results
    • If any failures were detected the test suite returns a failure