# Testcontainers
[](https://hex.pm/packages/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](#prerequisites)
- [Installation](#installation)
- [Usage](#usage)
- [API Documentation](#api-documentation)
- [Contributing](#contributing)
- [License](#license)
- [Contact](#contact)
## Prerequisites
Before you begin, ensure you have met the following requirements:
- You have installed the latest version of [Elixir](https://elixir-lang.org/install.html)
- 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`:
```elixir
def deps do
[
{:testcontainers, "~> x.x.x"}
]
end
```
2. Run mix deps.get
3. Add the following to test/test_helper.exs
```elixir
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:
```elixir
{: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:
```elixir
{:ok, _} = Testcontainers.start_link()
config = Testcontainers.RedisContainer.new()
{:ok, container} = Testcontainers.start_container(config)
```
### ExUnit tests
Given you have added Testcontainers.start_link() to test_helper.exs:
```elixir
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:
```elixir
import Testcontainers.ExUnit
container(:redis, Testcontainers.RedisContainer.new())
```
### In a Phoenix project:
To start a postgres container when running tests, that also enables testing of application initialization with database calls at startup, add this in application.ex:
```elixir
# in config/dev.exs:
config :testcontainers,
enabled: true
database: "hello_dev"
# in config/test.exs:
config :testcontainers,
enabled: true
# in lib/hello/application.ex:
@impl true
def start(_type, _args) do
if Application.get_env(:testcontainers, :enabled, false) do
{:ok, _container} =
case Application.get_env(:testcontainers, :database) do
nil ->
Testcontainers.Ecto.postgres_container(app: :hello)
database ->
Testcontainers.Ecto.postgres_container(
app: :hello,
persistent_volume_name: "#{database}_data"
)
end
end
# .. other setup code
end
# in mix.exs
# comment out test alias and setup aliases for ecto
defp aliases do
[
setup: [
"deps.get",
# "ecto.setup",
"assets.setup",
"assets.build"
],
# "ecto.setup": ["ecto.create", "ecto.migrate", "run priv/repo/seeds.exs"],
# "ecto.reset": ["ecto.drop", "ecto.setup"],
# test: ["ecto.create --quiet", "ecto.migrate --quiet", "test"],
# ... SNIP
]
end
```
This will start a postgres container that will be terminated when the test process ends.
The database config in config/test.exs will be temporarily updated in-memory with the random host port on the container, and other properties like username, password and database. In most cases these will default to "test" unless overridden.
See documentation on [Testcontainers.Ecto](https://hexdocs.pm/testcontainers/Testcontainers.Ecto.html) for more information about the options it can take.
There is an example repo here with a bare bones phoenix application, where the only changes are the use of the ecto function and removing the test alias that interferes with it:
[Phoenix example](./examples/phoenix_project)
There is also another example repo without Phoenix, just a bare mix project, which show cases that the ecto dependencies are in fact optional:
[Mix project](./examples/mix_project)
### Logging
By default, Testcontainers doesn't log anything. If you want Testcontainers to log, set the desired log level in config/test.exs:
```elixir
# config/test.exs
import Config
config :testcontainers,
log_level: :warning
```
## API Documentation
For more detailed information about the API, different container configurations, and advanced usage scenarios, please refer to the [API documentation](https://hexdocs.pm/testcontainers/api-reference.html).
## 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.
---
Thank you for using Testcontainers to test your Elixir applications!
