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HOWTO: Writing system tests for a package

Introduction

Elastic Packages are comprised of data streams. A system test exercises the end-to-end flow of data for a package's data stream — from ingesting data from the package's integration service all the way to indexing it into an Elasticsearch data stream.

Conceptual process

Conceptually, running a system test involves the following steps:

  1. Deploy the Elastic Stack, including Elasticsearch, Kibana, and the Elastic Agent. This step takes time so it should typically be done once as a pre-requisite to running system tests on multiple data streams.
  2. Enroll the Elastic Agent with Fleet (running in the Kibana instance). This step also can be done once, as a pre-requisite.
  3. Depending on the Elastic Package whose data stream is being tested, deploy an instance of the package's integration service.
  4. Create a test policy that configures a single data stream for a single package.
  5. Assign the test policy to the enrolled Agent.
  6. Wait a reasonable amount of time for the Agent to collect data from the integration service and index it into the correct Elasticsearch data stream.
  7. Delete test artifacts and tear down the instance of the package's integration service.
  8. Once all desired data streams have been system tested, tear down the Elastic Stack.

Limitations

At the moment system tests have limitations. The salient ones are:

  • They can only test packages whose integration services can be deployed via Docker Compose. Eventually they will be able to test packages that can be deployed via other means, e.g. a Terraform configuration.
  • They can only check for the existence of data in the correct Elasticsearch data stream. Eventually they will be able to test the shape and contents of the indexed data as well.

Defining a system test

Packages have a specific folder structure (only relevant parts shown).

<package root>/
  data_stream/
    <data stream>/
      manifest.yml
  manifest.yml

To define a system test we must define configuration at two levels: the package level and each data stream's level.

Package-level configuration

First, we must define the configuration for deploying a package's integration service. As mentioned in the Limitations section above, only packages whose integration services can be deployed via Docker Compose are supported at the moment.

<package root>/
  _dev/
    deploy/
      docker/
        docker-compose.yml

The docker-compose.yml file defines the integration service(s) for the package. If your package has a logs data stream, the log files from your package's integration service must be written to a volume. For example, the apache package has the following definition in it's integration service's docker-compose.yml file.

version: '2.3'
services:
  apache:
    # Other properties such as build, ports, etc.
    volumes:
      - ${SERVICE_LOGS_DIR}:/usr/local/apache2/logs

Here, SERVICE_LOGS_DIR is a special keyword. It is something that we will need later.

Data stream-level configuration

Next, we must define configuration for each data stream that we want to system test.

<package root>/
  data_stream/
    <data stream>/
      _dev/
        test/
          system/
            config.yml

The config.yml file allows you define values for package and data stream-level variables. For example, the apache/access data stream's config.yml is shown below.

vars: ~
data_stream:
  vars:
    paths:
      - "{{SERVICE_LOGS_DIR}}/access.log*"

The top-level vars field corresponds to package-level variables defined in the apache package's manifest.yml file. In the above example we don't override any of these package-level variables, so their default values, as specified in the apache package's manifest.yml file are used.

The data_stream.vars field corresponds to data stream-level variables for the current data stream (apache/access in the above example). In the above example we override the paths variable. All other variables are populated with their default values, as specified in the apache/access data stream's manifest.yml file.

Notice the use of the {{SERVICE_LOGS_DIR}} placeholder. This corresponds to the ${SERVICE_LOGS_DIR} variable we saw in the docker-compose.yml file earlier. In the above example, the net effect is as if the /usr/local/apache2/logs/access.log* files located inside the Apache integration service container become available at the same path from Elastic Agent's perspective.

Placeholders

The SERVICE_LOGS_DIR placeholder is not the only one available for use in a data stream's config.yml file. The complete list of available placeholders is shown below.

Placeholder name Data type Description
Hostname string Addressable host name of the integration service.
Ports []int Array of addressable ports the integration service is listening on.
Port int Alias for Ports[0]. Provided as a convenience.
Logs.Folder.Agent string Path to integration service's logs folder, as addressable by the Agent.
SERVICE_LOGS_DIR string Alias for Logs.Folder.Agent. Provided as a convenience.

Placeholders used in the config.yml must be enclosed in {{ and }} delimiters, per Handlebars syntax.

Running a system test

Once the two levels of configurations are defined as described in the previous section, you are ready to run system tests for a package's data streams.

First you must deploy the Elastic Stack. This corresponds to steps 1 and 2 as described in the Conceptual process section.

elastic-package stack up -d

For a complete listing of options available for this command, run elastic-package stack up -h or elastic-package help stack up.

Next, you must set environment variables needed for further elastic-package commands.

$(elastic-package stack shellinit)

Next, you must invoke the system tests runner. This corresponds to steps 3 through 7 as described in the Conceptual process section.

If you want to run system tests for all data streams in a package, navigate to the package's root folder (or any sub-folder under it) and run the following command.

elastic-package test system

If you want to run system tests for specific data streams in a package, navigate to the package's root folder (or any sub-folder under it) and run the following command.

elastic-package test system --data-streams <data stream 1>[,<data stream 2>,...]

Finally, when you are done running all system tests, bring down the Elastic Stack. This corresponds to step 8 as described in the Conceptual process section.

elastic-package stack down