# 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
    {

        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 as m;

    class TemperatureTest extends PHPUnit_Framework_TestCase
    {

        public function tearDown()
        {
            m::close();
        }

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

            $temperature = new Temperature($service);

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

    }

Note

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