<?php
require 'Calculator.php';

class TestCalculator extends PHPUnit_Framework_TestCase {
    
    private $calculator;
    
    protected function setUp() {
        $this->calculator = new Calculator();
    }
    
    protected function tearDown() {
        $this->calculator = NULL;
    }
    
    public function testAdd() {
        $result = $this->calculator->add(1, 2);
        $this->assertEquals(4, $result);
    }
    
}

<?php
class Calculator
{
    
    public function add($x, $y)
    {
       return $x + $y;
    }
    
}

class TestCalculator extends PHPUnit_Framework_TestCase {