dockertest

ory.am/dockertest

Use Docker to run your Go language integration tests against third party services on Microsoft Windows, Mac OSX and Linux! Dockertest uses Docker to spin up images on Windows and Mac OSX as well. Dockertest is based on docker.go from camlistore.

IMPORTANT
We strongly encourage you to move to dockertest v3 for new and existing projects. It has a much cleaner API, less dependencies and is less prone to errors. V3 will be eventually merged into master.

Dockertest currently supports these backends:

• PostgreSQL
• MySQL
• MongoDB
• NSQ
• Redis
• Elastic Search
• RethinkDB
• RabbitMQ
• Mockserver
• ActiveMQ
• ZooKeeper
• Cassandra
• Etcd
• Consul

Table of Contents

• Why should I use Dockertest?
• Installing and using Dockertest
  • Start a container
• Write awesome tests
  • Setting up Travis-CI
• Troubleshoot & FAQ
  • I need to use a specific container version for XYZ
  • My build is broken!
  • Out of disk space
  • I am using docker machine (OSX / Linux)
  • Removing old containers
  • Customized database

Why should I use Dockertest?

When developing applications, it is often necessary to use services that talk to a database system. Unit Testing these services can be cumbersome because mocking database/DBAL is strenuous. Making slight changes to the schema implies rewriting at least some, if not all of the mocks. The same goes for API changes in the DBAL. To avoid this, it is smarter to test these specific services against a real database that is destroyed after testing. Docker is the perfect system for running unit tests as you can spin up containers in a few seconds and kill them when the test completes. The Dockertest library provides easy to use commands for spinning up Docker containers and using them for your tests.

Installing and using Dockertest

Using Dockertest is straightforward and simple. Check the releases tab for available releases.

To install dockertest, run

go get gopkg.in/ory-am/dockertest.vX

where X is your desired version. For example:

go get gopkg.in/ory-am/dockertest.v2

Note: When using the Docker Toolbox (Windows / OSX), make sure that the VM is started by running docker-machine start default.

Start a container

package main

import (
	"gopkg.in/ory-am/dockertest.v2"
	"gopkg.in/mgo.v2"
	"time"
)

func main() {
	var db *mgo.Session
	c, err := dockertest.ConnectToMongoDB(15, time.Millisecond*500, func(url string) bool {
	    // This callback function checks if the image's process is responsive.
	    // Sometimes, docker images are booted but the process (in this case MongoDB) is still doing maintenance
	    // before being fully responsive which might cause issues like "TCP Connection reset by peer".
		var err error
		db, err = mgo.Dial(url)
		if err != nil {
			return false
		}

		// Sometimes, dialing the database is not enough because the port is already open but the process is not responsive.
		// Most database conenctors implement a ping function which can be used to test if the process is responsive.
		// Alternatively, you could execute a query to see if an error occurs or not.
		return db.Ping() == nil
	})

	if err != nil {
	    log.Fatalf("Could not connect to database: %s", err)
	}

	// Close db connection and kill the container when we leave this function body.
    defer db.Close()
	defer c.KillRemove()

	// The image is now responsive.
}

You can start PostgreSQL and MySQL in a similar fashion.

There are some cases where it’s useful to test how your application/code handles remote resources failing / shutting down. For example, what if your database goes offline? Does your application handle it gracefully?

This can be tested by stopping and starting an existing container:

	var hosts []string
	c, err := ConnectToZooKeeper(15, time.Millisecond*500, func(url string) bool {
		conn, _, err := zk.Connect([]string{url}, time.Second)
		if err != nil {
			return false
		}
		defer conn.Close()
		hosts = []string{url}

		return true
	})
	defer c.KillRemove()

	conn, _, _ := zk.Connect(hosts, time.Second)
	conn.Create("/test", []byte("hello"), 0, zk.WorldACL(zk.PermAll))

	c.Stop()

	_, _, err = zk.Get("/test") // err == zk.ErrNoServer

	c.Start()

	data, _, _ = zk.Get("/test") // data == []byte("hello")

It is also possible to start a custom container (in this example, a RabbitMQ container):

	c, ip, port, err := dockertest.SetupCustomContainer("rabbitmq", 5672, 10*time.Second)
	if err != nil {
		log.Fatalf("Could not setup container: %s", err
	}
	defer c.KillRemove()

	err = dockertest.ConnectToCustomContainer(fmt.Sprintf("%v:%v", ip, port), 15, time.Millisecond*500, func(url string) bool {
		amqp, err := amqp.Dial(fmt.Sprintf("amqp://%v", url))
		if err != nil {
			return false
		}
		defer amqp.Close()
		return true
	})

	...

Write awesome tests

It is a good idea to start up the container only once when running tests.

import (
	"fmt"
	"testing"
    "log"
	"os"

	"database/sql"
	_ "github.com/lib/pq"
	"gopkg.in/ory-am/dockertest.v2"
)

var db *sql.DB

func TestMain(m *testing.M) {
	c, err := dockertest.ConnectToPostgreSQL(15, time.Second, func(url string) bool {
	    // Check if postgres is responsive...
		var err error
		db, err = sql.Open("postgres", url)
		if err != nil {
			return false
		}
		return db.Ping() == nil
	})
	if err != nil {
		log.Fatalf("Could not connect to database: %s", err)
	}

	// Execute tasks like setting up schemata.

	// Run tests
	result := m.Run()

	// Close database connection.
	db.Close()

	// Clean up image.
	c.KillRemove()

	// Exit tests.
	os.Exit(result)
}

func TestFunction(t *testing.T) {
    // db.Exec(...
}

Setting up Travis-CI

You can run the Docker integration on Travis easily:

# Sudo is required for docker
sudo: required

# Enable docker
services:
  - docker

# In Travis, we need to bind to 127.0.0.1 in order to get a working connection. This environment variable
# tells dockertest to do that.
env:
  - DOCKERTEST_BIND_LOCALHOST=true

Troubleshoot & FAQ

I need to use a specific container version for XYZ

You can specify a container version by setting environment variables or globals. For more information, check vars.go.

My build is broken!

With v2, we removed all Open* methods to reduce duplicate code, unnecessary dependencies and make maintenance easier. If you relied on these, run go get gopkg.in/ory-am/dockertest.v1 and replace import "github.com/ory-am/dockertest" with import "gopkg.in/ory-am/dockertest.v1".

Out of disk space

Try cleaning up the images with docker-cleanup-volumes.

I am using docker machine (OSX / Linux)

First of all, consider upgrading! If that’s not an option, there are some steps you need to take:

• Set dockertest.UseDockerMachine = "1" or set the environment variable DOCKERTEST_LEGACY_DOCKER_MACHINE=1
• Set docker.BindDockerToLocalhost = "" or alternatively DOCKER_BIND_LOCALHOST=

Removing old containers

Sometimes container clean up fails. Check out this stackoverflow question on how to fix this.

Customized database

I am using postgres (or mysql) driver, how do I use customized database instead of default one? You can alleviate this helper function to do that, see testcase or example below:

func TestMain(m *testing.M) {
	if c, err := dockertest.ConnectToPostgreSQL(15, time.Second, func(url string) bool {
        customizedDB := "cherry" // here I am connecting cherry database
        newURL, err := SetUpPostgreDatabase(customizedDB, url)

        // or use SetUpMysqlDatabase for mysql driver

        if err != nil {
                log.Fatal(err)
        }
        db, err := sql.Open("postgres", newURL)
        if err != nil {
            return false
        }
        return db.Ping() == nil
    }); err != nil {
        log.Fatal(err)
    }