Simple Example

Imagine we have a Temperature class which samples the temperature of a locale before reporting an average temperature. The data could come from a web service or any other data source, but we do not have such a class at present. We can, however, assume some basic interactions with such a class based on its interaction with the Temperature class:

class Temperature
{
    private $service;

    public function __construct($service)
    {
        $this->service = $service;
    }

    public function average()
    {
        $total = 0;
        for ($i=0; $i<3; $i++) {
            $total += $this->service->readTemp();
        }
        return $total/3;
    }
}

Even without an actual service class, we can see how we expect it to operate. When writing a test for the Temperature class, we can now substitute a mock object for the real service which allows us to test the behaviour of the Temperature class without actually needing a concrete service instance.

use \Mockery;

class TemperatureTest extends PHPUnit_Framework_TestCase
{
    public function tearDown()
    {
        Mockery::close();
    }

    public function testGetsAverageTemperatureFromThreeServiceReadings()
    {
        $service = Mockery::mock('service');
        $service->shouldReceive('readTemp')
            ->times(3)
            ->andReturn(10, 12, 14);

        $temperature = new Temperature($service);

        $this->assertEquals(12, $temperature->average());
    }
}

We create a mock object which our Temperature class will use and set some expectations for that mock — that it should receive three calls to the readTemp method, and these calls will return 10, 12, and 14 as results.

Note

PHPUnit integration can remove the need for a tearDown() method. See “PHPUnit Integration” for more information.