Writing RSpec tests for charts

The following are notes and conventions used for creating RSpec tests for the GitLab chart.

Filtering RSpec tests

To aid in development it is possible to filter which tests are executed by adding the :focus tag to one or more tests. With the :focus tag only tests that have been specifically tagged will be run. This allows quick development and testing of new code without having to wait for all the RSpec tests to execute. The following is an example of a test that has been tagged with:focus.

describe 'some feature' do
  it 'generates output', :focus => true do

The :focus tag can be added to describe, context or it blocks which allows a test or a group of tests to be executed.

Generating YAML from the chart

Much of the testing of the chart is that it generates the correct YAML structure given a number of chart inputs. This is done using the HelmTemplate class as in the following:

obj = HelmTemplate.new(values)

The resulting obj encodes the YAML documents returned by the helm template command indexed by the Kubernetes object kind and the object name (metadata.name). This indexed valued is used by most of the methods to locate values within the YAML.

For example:

obj.dig('ConfigMap/test-gitaly', 'data', 'config.toml.erb')

This will return the contents of the config.toml.erb file contained in the test-gitaly ConfigMap.

Note: Using the HelmTemplate class will always use the release name of “test” when executing the helm template command.

Chart inputs

The input parameter to the HelmTemplate class constructor is a dictionary of values that represents the values.yaml that is used on the Helm command line. This dictionary mirrors the YAML structure of the values.yaml file.

describe 'some feature' do
  let(:default_values) do
    { 'certmanager-issuer' => { 'email' => 'test@example.com' } }

  describe 'global.feature.enabled' do
    let(:values) do
        'global' => {
          'feature' => {
            'enabled' => true


The above snippet demonstrates a common pattern of setting a number of default values that are common across multiple tests that are then merged into the final values that are used in the HelmTemplate constructor for a specific set of tests.

Testing the results

The HelmTemplate object has a number of methods that assist with writing RSpec tests. The following are a summary of the available methods.

  • .exit_code()

This returns the exit code of the helm template command used to create the YAML documents that instantiates the chart in the Kubernetes cluster. A successful completion of the helm template will return an exit code of 0.

  • .dig(key, ...)

Walk down the YAML document returned by the HelmTemplate instance and return the value residing at the last key. If no value is found, then nil is returned.

  • .volumes(item)

Return an array of all the volumes for the specified deployment object. The returned array is a direct copy of the volumes key from the deployment object.

  • .find_volume(item, volume_name)

Return a dictionary of the specified volume from the specified deployment object.

  • .projected_volume_sources(item, mount_name)

Return an array of sources for the specified projected volume. The returned array has the following structure:

- secret:
    name: test-rails-secret
     - key: secrets.yml
       path: rails-secrets/secrets.yml
  • .stderr()

Return the STDERR output from the execution of helm template command.

  • .values()

Return a dictionary of all values that were used in the execution of the helm template command.