Testing traits (Intermediate)

Traits are a new concept introduced in PHP 5.4. Similar to Abstract classes they cannot be instantiated directly. You can always create a test class that uses a particular trait to test the functionality in that trait. However, PHPUnit has built-in functionality to dynamically create classes that use traits. This allows for simple testing of traits.

How to do it...

Consider a modified version of the CardCollection class that is, instead, represented as a trait.

<?php

trait CardCollectionTrait
{
  //...
  public function count()
  {
    return count($this->cards);
  }
  //...
}

You can create a test similar to what was created earlier for the CardCollection class.

<?php
class CardCollectionTraitTest extends PHPUnit_Framework_TestCase
{
  private $cardCollection;

  public function setUp()
  {
    $this->cardCollection = $this->getObjectForTrait('CardCollectionTrait');
  }

  public function testCountOnEmpty()
  {
    $this->assertEquals(0, $this->cardCollection->count());
  }
  //...
}

How it works...

Similar to how PHPUnit can be used to generate concrete implementations of abstract classes, it can also be used to generate a user of a given trait. The PHPUnit_Framework_TestCase::getObjectForTrait() method will generate and instantiate a class that uses the trait you pass as the first argument. You can then test the trait as you would test any other class.