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Helios Testing Framework

The Helios testing framework lets you deploy multiple services as docker containers, and run automated tests against them. The tests can be run locally or as part of an automated build. You can use the containers available in the Docker Registry, as well as containers built on your local machine.

The framework integrates with standard JUnit tests, and provides a JUnit rule called TemporaryJobs. This rule is the starting point for using the framework, and is used to define helios jobs, deploy them, and automatically undeploy them when the tests have completed.


  1. Make sure running mvn package builds your service into a docker container. You can do this with the docker-maven-plugin, by binding the build goal to the package lifecycle phase. When we run mvn verify we'll want to build the image first, and binding to the package phase lets us do that.

  2. Add helios-testing to your pom.xml in the element. Use the latest version if a newer one is available.

  3. Add the failsafe plugin to your pom.xml within the element.

  4. Create an integration test for your service following the examples below. The filename must end in “” so that maven's failsafe plugin will recognize it as an integration test.

  5. Run mvn verify

This basic example shows how to deploy a single service called Wiggum.

package com.spotify.wiggum;


import com.spotify.helios.testing.TemporaryJob;
import com.spotify.helios.testing.TemporaryJobs;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;

import static org.junit.Assert.assertEquals;

public class ServiceIT {

  public TemporaryJobs temporaryJobs = TemporaryJobs.create();

  private final HttpClient client = new DefaultHttpClient();

  private TemporaryJob temporaryJob;

  public void setup() {
    // Deploy the wiggum image created during the last build.The wiggum container will be listening
    // on a dynamically allocated port. 4229 is the port wiggum listens on in the container.
    temporaryJob = temporaryJobs.job()
        .port("wiggum", 4229)

  public void testPing() throws Exception {    
    // send a request to a /ping endpoint using the host and dynamically
    // allocated port of the job
    HostAndPort port = temporaryJob.address("wiggum");
    String pingUri = String.format("http://%s:%d/ping",

    HttpResponse response = client.execute(new HttpGet(pingUri));
    assertEquals("ping failed", 200, response.getStatusLine().getStatusCode());

This example deploys cassandra, memcached, and a service called foobar. Helios will register cassandra and memcached with a service discovery mechanism using the service registration plugin. Foobar will then lookup each service via that mechanism, just as it would in production.

package com.spotify.foobar;


import com.spotify.helios.testing.TemporaryJob;
import com.spotify.helios.testing.TemporaryJobs;

import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;

public class SystemIT {

  public final TemporaryJobs temporaryJobs = TemporaryJobs.create();

  private Client client;

  public void setup() throws Exception {

    final TemporaryJob cassandra = temporaryJobs.job()
        .port("cassandra", 9160)
        .registration("cassandra", "tcp", "cassandra")

    final TemporaryJob memcached = temporaryJobs.job()
        .env("MEMORY", "16")
        .port("memcached", 11211)
        .registration("memcached", "tcp", "memcached")

    final TemporaryJob foobar = temporaryJobs.job()
        .env("CASSANDRA_MAX_CONNS_PER_HOST", String.valueOf(1))
        .port("foobar", 9600)

    client = new Client("tcp://" + foobar.address("foobar"));

    final HostAndPort address = cassandra.address("cassandra");
    final CassandraClient cassandraClient = new CassandraClient();
    cassandraClient.connect(address.getHost(), address.getPort());

  public void test() throws Exception {

Note that cassandra and memcached register themselves using Helios's service registration mechanism. Foobar can then discover how to reach them at runtime. Another option would be to pass Foobar their endpoints via environment variables like this:

final TemporaryJob foobar = temporaryJobs.job()
    .env("MEMCACHED_ADDRESS", memcached.address("memcached")
    .env("CASSANDRA_ADDRESS", cassandra.addresses("cassandra")
    .env("CASSANDRA_MAX_CONNS_PER_HOST", String.valueOf(1))
    .env("CASSANDRA_MAX_CONNS_PER_HOST", String.valueOf(1))
    .port("foobar", 9600)

Environment Configuration

There are 3 environment variables you can use to configure the test to run in different environments.

  • HELIOS_DOMAIN - the domain where the helios master can be reached.
  • HELIOS_ENDPOINTS - the specific endpoint(s) to connect to. When set, this overrides HELIOS_DOMAIN.
  • HELIOS_HOST_FILTER - regular expression or FQDN of the helios host you want to deploy to. If more than one host matches the regex, one will be selected randomly.

If neither HELIOS_DOMAIN nor HELIOS_ENDPOINTS is set, TemporaryJobs will connect to tcp://localhost:5801 and set HELIOS_HOST_FILTER to .+. HELIOS_HOST_FILTER must be set if either HELIOS_DOMAIN or HELIOS_ENDPOINTS is set.

Configuration By File

It may be that for your site, there are common environment variables or other settings which you want most/all TemporaryJob based tests to have. Rather than have to subclass the framework or hack things, or whatnot, you can specify configuration profiles for these kinds of things to save the boilerplate that would otherwise wind up in your code. The Helios Testing Framework uses the Typesafe Config Library to accomplish this. Within a profile, the following keys having meaning:

  • name - string -- same as the method.
  • version - string -- same as the TemporaryJobBuilder.version() method.
  • image - string -- same as the TemporaryJobBuilder.image() method.
  • command - a list of strings -- same as the TemporaryJobBuilder.command() method
  • host - string -- same as the method.
  • deploy - string -- same as the TemporaryJobBuilder.deploy() method.
  • imageInfoFile - string -- same as the TemporaryJobBuilder.imageInfoFile() method.
  • env - map of string:string -- same as the TemporaryJobBuilder.env() method with entries from the map.
  • registrationDomain - string -- same as the TemporaryJobBuilder.registrationDomain() method.
  • user - string -- same as the TemporaryJobsbuilder.user() method.
  • hostFilter - string -- same as the TemporaryJobsbuilder.hostFilter() method.
  • domain - string -- same as the TemporaryJobsbuilder.domain() method.
  • endpoints - list of string -- same as the TemporaryJobsbuilder.endpoints() method.
  • jobDeployedMessageFormat - string -- a string format for Apache StrSubstitutor to log a custom message when the job has started -- available substitutions are [host, name, version, hash, containerId, image, job] - useful to log a link where container logs might be found.
  • hostPickingStrategy - string -- one of
    • random (the default) - randomly pick a host for each temporary job.
    • onerandom - randomly pick a host and deploy all temporary jobs there
    • deterministic - seed the random number generator so it "randomly" picks the same hosts across test runs that it did in previous runs. You must specify hostPickingStrategyKey.
    • onedetermistic - seed the random number generator so it "randomly" picks the same host on which it deploys all jobs across test runs. You must specify hostPickingStrategyKey.
  • hostPickingStrategyKey - string - a string used to seed the random number generator. It can be basically anything, but it's best for it to not be empty.
  • heliosClientHttpTimeoutSeconds - int - an integer with the timeout in seconds used by the HeliosClient http requests to the Helios API.

There's also the prefix config variable, which is useless to set, but useful to reference from some of the above variables if you want the randomized prefix generated by the framework for other purposes.

Instead of the normal application.conf and reference.conf files that Typesafe uses, the testing framework uses helios.conf and helios-base.conf respectively for these roles.

A sample helios.conf file (or helios-base.conf) you could put in your project might be:

helios.testing.profile : foo
helios.testing.profiles {
  foo : {
    env : {
      ## Do beware that the ${prefix} is *not* enclosed in double quotes.
      MYJOBPREFIX : "something before ["${prefix}"] after"
    hostFilter : "*testagent*"
  bar : {
    env : {
      MYJOBPREFIX : "hahahah! no prefix for you!"

You can also consult the helios-base.conf and helios.conf files for an example.

Also, any settings on the builders in code will override what's in the file.

If the profile specified either to the builder directly, or by the profile setting does not exist, you'll get a failure. If there is no profile set, this is still ok. Since we're using the Typesafe Library, you can then make the default profile settable by java property or environment variable, which can then be configured via Maven (if you're using it) profiles.

You can specify the profile via mvn when running tests by:

mvn -Dhelios.testing.profile=myprofile other maven arguments here....

Job Cleanup

When a test completes, the TemporaryJobs rule will undeploy and delete all jobs it created during the test. If the test process is killed before the test completes, the jobs will be left running. Helios handles this in two ways.

  1. Each time TemporaryJobs is created, it will attempt to remove any jobs leftover from previous runs.

  2. TemporaryJobs sets a time-to-live on each job it creates. This defaults to 30 minutes, but can be overridden if needed.


Debugging containers can be more difficult than if it were running outside a container. Fortunately, it can be made a little simpler with Java because it supports remote debugging. What you need to do is add the following to your java command line before the class or jar you will run:

-Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=y

For example:

java -Xdebug -Xrunjdwp:transport=dt_socket,address=8001,server=y,suspend=y \ \
    -cp ./helios-services/target/helios-services-0.8.25-SNAPSHOT-shaded.jar \

And then make sure you define the port mapping for port 8001. You can set your container not to wait for the debugger connection by changing suspend=y to suspend=n, but chances are good you probably don't want to do that. Additionally, you can choose a port other than 8001, just make sure your port mapping is adjusted accordingly.

After that, when your test spins up the container in question, use the helios tools to find out:

  1. where your container was spun up
  2. what port was chosen if not using static port allocation

Then, from here I assume you already know how to do remote debugging with your IDE of choice.

Pro Tip In general, it will be easier for debugging if you fix the host you're going to run the test on, as well as using static port allocation; this way you don't have to fiddle to reconfigure the debug settings in your IDE for every test run.