# Introduction

## What's Brain Monkey

Brain Monkey is a unit test utility for PHP.

It comes with 2 group of features:

* the first allow **mocking and testing any PHP function**. This part is a general tool and two times framework agnostic: can be used to test code that uses any frameworks \(or no framework\) and in combination with any testing framework.
* the second group of features can be used with any testing framework as well, but is **specific to test WordPress code**.

  Who is interested in the first part can use only it, just like this second group of features does not exists.

## Why Brain Monkey

When unit tests are done in the right way, the SUT \(System Under Test\) must be tested in **isolation**.

Long story short, it means that any _external_ code used in the SUT must be assumed as perfectly working.

This is a key concept in unit tests.

In PHP, to create "mock" and "stubs" for objects is a pretty easy task, framework like [PHPUnit](https://phpunit.de/manual/current/en/test-doubles.html) or [phpspec](https://www.phpspec.net/en/latest/manual/prophet-objects.html) have embedded features to do that, and libraries like [Mockery](https://github.com/padraic/mockery) make it even easier.

But when _external_ code make use of **functions** things become harder, because PHP testing framework can't mock or monkey patch functions.

This is where Brain Monkey comes into play: its aim is to bring that easiness to function testing.

This involves:

* define functions if not defined
* allow to enforce function behavior
* allow to set expectations on function execution

Moreover, I have to admit that I coded Brain Monkey to test WordPress code \(that makes a large use of global functions\).

This is the reason why Brain Monkey comes with a set of WordPress-specific tools, but the ability to monkey patch and test functions is independent from WordPress-specific tools and can be used to test any PHP code.

### Under the hood

Brain Monkey gets all its power from two great libraries: [**Mockery**](http://docs.mockery.io/) and [**Patchwork**](http://patchwork2.org/).

What actually Brain Monkey does is to connect the _function redefinition_ feature of Patchwork with the powerful testing mechanism and DSL provided by Mockery, and thanks to that Brain Monkey has:

* PHPUnit, PHPSpec or any other testing framework compatibility
* powerful and succinct API with human readable syntax

All the rest is joy.

### PHP versions compatibility

Currently, Brain Monkey supports PHP 5.6+.