---
title: Four-Phase Test
teaser:
tags: web,ruby,testing
author: Dan Croak
published_on: 2012-09-28
---

The [Four-Phase Test](http://xunitpatterns.com/Four%20Phase%20Test.html) is a
testing pattern, applicable to all programming languages and unit tests (not so
much integration tests).

It takes the following general form:

```ruby
test do
  setup
  exercise
  verify
  teardown
end
```

There are four distinct phases of the test. They are executed sequentially.

## setup

During setup, the system under test (usually a class, object, or method) is set up.

```ruby
user = User.new(password: 'password')
```

## exercise

During exercise, the system under test is executed.

```ruby
user.save
```

## verify

During verification, the result of the exercise is verified against the
developer's expectations.

```ruby
user.encrypted_password.should_not be_nil
```

## teardown

During teardown, the system under test is reset to its pre-setup state.

This is usually handled implicitly by the language (releasing memory) or test
framework (running inside a database transaction).

## all together

The four phases are wrapped into a named test to be referenced individually.

Our [style guide](https://github.com/thoughtbot/guides/tree/master/style)
advises we "Separate setup, exercise, verification, and teardown phases with
newlines."

```ruby
it 'encrypts the password' do
  user = User.new(password: 'password')

  user.save

  user.encrypted_password.should_not be_nil
end
```

Go forth and test in phases.