# Prophecy
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Prophecy is a highly opinionated yet very powerful and flexible PHP object mocking
framework. Though initially it was created to fulfil phpspec2 needs, it is flexible
enough to be used inside any testing framework out there with minimal effort.
## A simple example
```php
<?php
class UserTest extends PHPUnit_Framework_TestCase
{
private $prophet;
public function testPasswordHashing()
{
$hasher = $this->prophet->prophesize('App\Security\Hasher');
$user = new App\Entity\User($hasher->reveal());
$hasher->generateHash($user, 'qwerty')->willReturn('hashed_pass');
$user->setPassword('qwerty');
$this->assertEquals('hashed_pass', $user->getPassword());
}
protected function setup()
{
$this->prophet = new \Prophecy\Prophet;
}
protected function tearDown()
{
$this->prophet->checkPredictions();
}
}
```
## Installation
### Prerequisites
Prophecy requires PHP 5.3.3 or greater.
### Setup through composer
First, add Prophecy to the list of dependencies inside your `composer.json`:
```json
{
"require-dev": {
"phpspec/prophecy": "~1.0"
}
}
```
Then simply install it with composer:
```bash
$> composer install --prefer-dist
```
You can read more about Composer on its [official webpage](http://getcomposer.org).
## How to use it
First of all, in Prophecy every word has a logical meaning, even the name of the library
itself (Prophecy). When you start feeling that, you'll become very fluid with this
tool.
For example, Prophecy has been named that way because it concentrates on describing the future
behavior of objects with very limited knowledge about them. But as with any other prophecy,
those object prophecies can't create themselves - there should be a Prophet:
```php
$prophet = new Prophecy\Prophet;
```
The Prophet creates prophecies by *prophesizing* them:
```php
$prophecy = $prophet->prophesize();
```
The result of the `prophesize()` method call is a new object of class `ObjectProphecy`. Yes,
that's your specific object prophecy, which describes how your object would behave
in the near future. But first, you need to specify which object you're talking about,
right?
```php
$prophecy->willExtend('stdClass');
$prophecy->willImplement('SessionHandlerInterface');
```
There are 2 interesting calls - `willExtend` and `willImplement`. The first one tells
object prophecy that our object should extend specific class, the second one says that
it should implement some interface. Obviously, objects in PHP can implement multiple
interfaces, but extend only one parent class.
### Dummies
Ok, now we have our object prophecy. What can we do with it? First of all, we can get
our object *dummy* by revealing its prophecy:
```php
$dummy = $prophecy->reveal();
```
The `$dummy` variable now holds a special dummy object. Dummy objects are objects that extend
and/or implement preset classes/interfaces by overriding all their public methods. The key
point about dummies is that they do not hold any logic - they just do nothing. Any method
of the dummy will always return `null` and the dummy will never throw any exceptions.
Dummy is your friend if you don't care about the actual behavior of this double and just need
a token object to satisfy a method typehint.
You need to understand one thing - a dummy is not a prophecy. Your object prophecy is still
assigned to `$prophecy` variable and in order to manipulate with your expectations, you
should work with it. `$dummy` is a dummy - a simple php object that tries to fulfil your
prophecy.
### Stubs
Ok, now we know how to create basic prophecies and reveal dummies from them. That's
awesome if we don't care about our _doubles_ (objects that reflect originals)
interactions. If we do, we need to use *stubs* or *mocks*.
A stub is an object double, which doesn't have any expectations about the object behavior,
but when put in specific environment, behaves in specific way. Ok, I know, it's cryptic,
but bear with me for a minute. Simply put, a stub is a dummy, which depending on the called
method signature does different things (has logic). To create stubs in Prophecy:
```php
$prophecy->read('123')->willReturn('value');
```
Oh wow. We've just made an arbitrary call on the object prophecy? Yes, we did. And this
call returned us a new object instance of class `MethodProphecy`. Yep, that's a specific
method with arguments prophecy. Method prophecies give you the ability to create method
promises or predictions. We'll talk about method predictions later in the _Mocks_ section.
#### Promises
Promises are logical blocks, that represent your fictional methods in prophecy terms
and they are handled by the `MethodProphecy::will(PromiseInterface $promise)` method.
As a matter of fact, the call that we made earlier (`willReturn('value')`) is a simple
shortcut to:
```php
$prophecy->read('123')->will(new Prophecy\Promise\ReturnPromise(array('value')));
```
This promise will cause any call to our double's `read()` method with exactly one
argument - `'123'` to always return `'value'`. But that's only for this
promise, there's plenty others you can use:
- `ReturnPromise` or `->willReturn(1)` - returns a value from a method call
- `ReturnArgumentPromise` or `->willReturnArgument($index)` - returns the nth method argument from call
- `ThrowPromise` or `->willThrow` - causes the method to throw specific exception
- `CallbackPromise` or `->will($callback)` - gives you a quick way to define your own custom logic
Keep in mind, that you can always add even more promises by implementing
`Prophecy\Promise\PromiseInterface`.
#### Method prophecies idempotency
Prophecy enforces same method prophecies and, as a consequence, same promises and
predictions for the same method calls with the same arguments. This means:
```php
$methodProphecy1 = $prophecy->read('123');
$methodProphecy2 = $prophecy->read('123');
$methodProphecy3 = $prophecy->read('321');
$methodProphecy1 === $methodProphecy2;
$methodProphecy1 !== $methodProphecy3;
```
That's interesting, right? Now you might ask me how would you define more complex
behaviors where some method call changes behavior of others. In PHPUnit or Mockery
you do that by predicting how many times your method will be called. In Prophecy,
you'll use promises for that:
```php
$user->getName()->willReturn(null);
// For PHP 5.4
$user->setName('everzet')->will(function () {
$this->getName()->willReturn('everzet');
});
// For PHP 5.3
$user->setName('everzet')->will(function ($args, $user) {
$user->getName()->willReturn('everzet');
});
// Or
$user->setName('everzet')->will(function ($args) use ($user) {
$user->getName()->willReturn('everzet');
});
```
And now it doesn't matter how many times or in which order your methods are called.
What matters is their behaviors and how well you faked it.
#### Arguments wildcarding
The previous example is awesome (at least I hope it is for you), but that's not
optimal enough. We hardcoded `'everzet'` in our expectation. Isn't there a better
way? In fact there is, but it involves understanding what this `'everzet'`
actually is.
You see, even if method arguments used during method prophecy creation look
like simple method arguments, in reality they are not. They are argument token
wildcards. As a matter of fact, `->setName('everzet')` looks like a simple call just
because Prophecy automatically transforms it under the hood into:
```php
$user->setName(new Prophecy\Argument\Token\ExactValueToken('everzet'));
```
Those argument tokens are simple PHP classes, that implement
`Prophecy\Argument\Token\TokenInterface` and tell Prophecy how to compare real arguments
with your expectations. And yes, those cl
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