# 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.