# ExMachina
[](https://circleci.com/gh/thoughtbot/ex_machina)
**ExMachina is part of the [thoughtbot Elixir family][elixir-phoenix] of projects.**
ExMachina makes it easy to create test data and associations. It works great
with Ecto, but is configurable to work with any persistence library.
> **This README follows master, which may not be the currently published version**. Here are the
[docs for the latest published version of ExMachina](https://hexdocs.pm/ex_machina/README.html).
## Installation
#### To install in all environments (useful for generating seed data in dev/prod):
In `mix.exs`, add the ExMachina dependency:
```elixir
def deps do
# Get the latest from hex.pm. Works with Ecto 2.0
[{:ex_machina, "~> 2.0"}]
end
```
And start the ExMachina application. For most projects (such as
Phoenix apps) this will mean adding `:ex_machina` to the list of applications in
`mix.exs`. You can skip this step if you are using Elixir 1.4
```elixir
def application do
[mod: {MyApp, []},
applications: [:ex_machina, :other_apps...]]
end
```
#### Install in just the test environment with Phoenix:
In `mix.exs`, add the ExMachina dependency:
```elixir
def deps do
[{:ex_machina, "~> 2.0", only: :test}]
end
```
Add your factory module inside `test/support` so that it is only compiled in the
test environment.
Next, be sure to start the application in your `test/test_helper.exs` before
ExUnit.start:
```elixir
{:ok, _} = Application.ensure_all_started(:ex_machina)
```
#### Install in just the test environment for non-Phoenix projects:
You will follow the same instructions as above, but you will also need to add
`test/support` to your compilation paths (elixirc_paths) if you have not done
so already.
In `mix.exs`, add test/support to your elixirc_paths for just the test env.
```elixir
def project do
[app: ...,
# Add this if it's not already in your project definition.
elixirc_paths: elixirc_paths(Mix.env)]
end
# This makes sure your factory and any other modules in test/support are compiled
# when in the test environment.
defp elixirc_paths(:test), do: ["lib", "web", "test/support"]
defp elixirc_paths(_), do: ["lib", "web"]
```
## Overview
[Check out the docs](http://hexdocs.pm/ex_machina/ExMachina.html) for more details.
Define factories:
```elixir
defmodule MyApp.Factory do
# with Ecto
use ExMachina.Ecto, repo: MyApp.Repo
# without Ecto
use ExMachina
def user_factory do
%MyApp.User{
name: "Jane Smith",
email: sequence(:email, &"email-#{&1}@example.com"),
}
end
def article_factory do
%MyApp.Article{
title: "Use ExMachina!",
# associations are inserted when you call `insert`
author: build(:user),
}
end
def comment_factory do
%MyApp.Comment{
text: "It's great!",
article: build(:article),
}
end
end
```
Using factories ([check out the docs](http://hexdocs.pm/ex_machina/ExMachina.html) for more details):
```elixir
# `attrs` are automatically merged in for all build/insert functions.
# `build*` returns an unsaved comment.
# Associated records defined on the factory are built.
attrs = %{body: "A comment!"} # attrs is optional. Also accepts a keyword list.
build(:comment, attrs)
build_pair(:comment, attrs)
build_list(3, :comment, attrs)
# `insert*` returns an inserted comment. Only works with ExMachina.Ecto
# Associated records defined on the factory are inserted as well.
insert(:comment, attrs)
insert_pair(:comment, attrs)
insert_list(3, :comment, attrs)
# `params_for` returns a plain map without any Ecto specific attributes.
# This is only available when using `ExMachina.Ecto`.
params_for(:comment, attrs)
# `params_with_assocs` is the same as `params_for` but inserts all belongs_to
# associations and sets the foreign keys.
# This is only available when using `ExMachina.Ecto`.
params_with_assocs(:comment, attrs)
# Use `string_params_for` to generate maps with string keys. This can be useful
# for Phoenix controller tests.
string_params_for(:comment, attrs)
string_params_with_assocs(:comment, attrs)
```
## Usage in a test
```elixir
# Example of use in Phoenix with a factory that uses ExMachina.Ecto
defmodule MyApp.MyModuleTest do
use MyApp.ConnCase
# If using Phoenix, import this inside the using block in MyApp.ConnCase
import MyApp.Factory
test "shows comments for an article" do
conn = conn()
article = insert(:article)
comment = insert(:comment, article: article)
conn = get conn, article_path(conn, :show, article.id)
assert html_response(conn, 200) =~ article.title
assert html_response(conn, 200) =~ comment.body
end
end
```
## Where to put your factories
If you are using ExMachina in all environments:
> Start by creating one factory module (such as `MyApp.Factory`) in
`lib/my_app/factory.ex` and putting all factory definitions in that module.
If you are using ExMachina in only the test environment:
> Start by creating one factory module (such as `MyApp.Factory`) in
`test/support/factory.ex` and putting all factory definitions in that module.
Later on you can easily create different factories by creating a new module in
the same directory. This can be helpful if you need to create factories that are
used for different repos, your factory module is getting too big, or if you have
different ways of saving the record for different types of factories.
## Ecto Associations
ExMachina will automatically save any associations when you call any of the
`insert` functions. This includes `belongs_to` and anything that is
inserted by Ecto when using `Repo.insert!`, such as `has_many`, `has_one`,
and embeds. Since we automatically save these records for you, we advise that
factory definitions only use `build/2` when declaring associations, like so:
```elixir
def article_factory do
%Article{
title: "Use ExMachina!",
# associations are inserted when you call `insert`
comments: [build(:comment)],
author: build(:user),
}
end
```
Using `insert/2` in factory definitions may lead to performance issues and bugs,
as records will be saved unnecessarily.
## Flexible Factories with Pipes
```elixir
def make_admin(user) do
%{user | admin: true}
end
def with_article(user) do
insert(:article, user: user)
user
end
build(:user) |> make_admin |> insert |> with_article
```
## Using with Phoenix
If you want to keep the factories somewhere other than `test/support`,
change this line in `mix.exs`:
```elixir
# Add the folder to the end of the list. In this case we're adding `test/factories`.
defp elixirc_paths(:test), do: ["lib", "web", "test/support", "test/factories"]
```
## Custom Strategies
You can use ExMachina without Ecto, by using just the `build` functions, or you
can define one or more custom strategies to use in your factory. You can also
use custom strategies with Ecto. Here's an example of a strategy for json
encoding your factories. See the docs on [ExMachina.Strategy] for more info.
[ExMachina.Strategy]: https://hexdocs.pm/ex_machina/ExMachina.Strategy.html
```elixir
defmodule MyApp.JsonEncodeStrategy do
use ExMachina.Strategy, function_name: :json_encode
def handle_json_encode(record, _opts) do
Poison.encode!(record)
end
end
defmodule MyApp.Factory do
use ExMachina
# Using this will add json_encode/2, json_encode_pair/2 and json_encode_list/3
use MyApp.JsonEncodeStrategy
def user_factory do
%User{name: "John"}
end
end
# Will build and then return a JSON encoded version of the user.
MyApp.Factory.json_encode(:user)
```
## Contributing
Before opening a pull request, please open an issue first.
$ git clone https://github.com/thoughtbot/ex_machina.git
$ cd ex_machina
$ mix deps.get
$ mix test
Once you've made your additions and `mix test` passes, go ahead and open a PR!
## License
ExMachina is Copyright © 2015 thoughtbot. It is free software, and may be
redistributed under the terms specified in the [LICENSE](/LICENSE) file.
## About thoughtbot
ExMachina is maintained and funded by thoughtbot, inc.
The names and logos for thoughtbot are trademarks of thoughtbot, inc.
We love open source software, Elixir, and Phoenix. See [our other Elixir
projects][elixir-phoenix], or [hire our Elixir Phoenix development team][hire]
to design, develop, and grow your product.
[elixir-phoenix]: https://thoughtbot.com/services/elixir-phoenix?utm_source=github
[hire]: https://thoughtbot.com?utm_source=github
## Inspiration
* [Fixtures for Ecto](http://blog.danielberkompas.com/elixir/2015/07/16/fixtures-for-ecto.html)
* [Factory Girl](https://github.com/thoughtbot/factory_girl)
