Testcontainers

Testcontainers is an Elixir library that supports ExUnit tests, providing lightweight, throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container.

Table of Contents

• Prerequisites
• Installation
• Usage
• API Documentation
• Contributing
• License
• Contact

Prerequisites

Before you begin, ensure you have met the following requirements:

• You have installed the latest version of Elixir
• You have a Docker runtime installed
• You are familiar with Elixir and Docker basics

Installation

To add Testcontainers to your project, follow these steps:

1. Add testcontainers to your list of dependencies in mix.exs:

def deps do
  [
    {:testcontainers, "~> 1.11"}
  ]
end

2. Run mix deps.get

3. Add the following to test/test_helper.exs

Testcontainers.start_link()

Usage

This section explains how to use the Testcontainers library in your own project.

Basic usage

You can use generic container api, where you have to define everything yourself:

{:ok, _} = Testcontainers.start_link()
config = %Testcontainers.Container{image: "redis:5.0.3-alpine"}
{:ok, container} = Testcontainers.start_container(config)

Or you can use one of many predefined containers like RedisContainer, that has waiting strategies among other things defined up front with good defaults:

{:ok, _} = Testcontainers.start_link()
config = Testcontainers.RedisContainer.new()
{:ok, container} = Testcontainers.start_container(config)

If you want to use a predefined container, such as RedisContainer, with an alternative image, for example, valkey/valkey, it's possible:

{:ok, _} = Testcontainers.start_link()
config =
  Testcontainers.RedisContainer.new()
  |> Testcontainers.RedisContainer.with_image("valkey/valkey:latest")
  |> Testcontainers.RedisContainer.with_check_image("valkey/valkey")
{:ok, container} = Testcontainers.start_container(config)

ExUnit tests

Given you have added Testcontainers.start_link() to test_helper.exs:

setup 
  config = Testcontainers.RedisContainer.new()
  {:ok, container} = Testcontainers.start_container(config)
  ExUnit.Callbacks.on_exit(fn -> Testcontainers.stop_container(container.container_id) end)
  {:ok, %{redis: container}}
end

there is a macro that can simplify this down to a oneliner:

import Testcontainers.ExUnit

container(:redis, Testcontainers.RedisContainer.new())

Run tests in a Phoenix project (or any project for that matter)

To run/wrap testcontainers around a project use the testcontainers.test task.

mix testcontainers.test [--database postgres|mysql] [--watch dir ...]

to use postgres you can just run

mix testcontainers.test since postgres is default.

in your config/test.exs you can then change the repo config to this:

config :my_app, MyApp.Repo,
  username: System.get_env("DB_USER") || "postgres",
  password: System.get_env("DB_PASSWORD") || "postgres",
  hostname: System.get_env("DB_HOST") || "localhost",
  port: System.get_env("DB_PORT") || "5432",
  database: "my_app_test#{System.get_env("MIX_TEST_PARTITION")}",
  pool: Ecto.Adapters.SQL.Sandbox,
  pool_size: System.schedulers_online() * 2

Activate reuse of database containers started by mix task with adding testcontainers.reuse.enable=true in ~/.testcontainers.properties. This is experimental.

You can pass arguments to mix test by append -- to the of the command like this:

mix testcontainers.test -- --exclude flaky --stale

In the example above we are excluding flaky tests and using the --stale option.

Logging

Testcontainers use the standard Logger, see https://hexdocs.pm/logger/Logger.html.

API Documentation

For more detailed information about the API, different container configurations, and advanced usage scenarios, please refer to the API documentation.

Windows support

Testcontainers Desktop

This is the supported way to use Testcontainers Elixir on Windows. Download Testcontainers Desktop, install it and everything just works.

Native

You can run on windows natively with elixir and erlang. But its not really supported, but I have investigated and tried it out. These are my findings:

First install Visual Studio 2022 with Desktop development with C++.

Open visual studio dev shell. I do it by just opening an empty c++ project, then View -> Terminal.

Enable "Expose daemon on tcp://localhost:2375 without TLS" in Docker settings.

for powershell:

$Env:DOCKER_HOST = "tcp://localhost:2375"

for cmd:

set DOCKER_HOST=tcp://localhost:2375

Compile and run tests:

mix deps.get

mix deps.compile

mix test

Contributing

We welcome your contributions! Please see our contributing guidelines (TBD) for more details on how to submit patches and the contribution workflow.

License

Testcontainers is available under the MIT license. See the LICENSE file for more info.

Contact

If you have any questions, issues, or want to contribute, feel free to contact us.

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Thank you for using Testcontainers to test your Elixir applications!