Thinking about unit tests and how you think about your functions and how you write your tests.

gistfile1.php

<?php

class Foo
{
    private $bar;

    public function setBar($bar)
    {
        $this->bar = $bar;
    }

    public function getBar()
    {
        return $this->bar;
    }
}

class FooTest extends PHPUnit_Framework_TestCase
{
    protected $foo;

    public function setUp()
    {
        $this->foo = new Foo();
    }

    public function testSetBarUpdatesBarAttribute()
    {
        $this->foo->setBar('logan');
        $this->assertAttributeEquals('logan', 'bar', $this->foo);
    }

    public function testSetBarSetsReturnValueOfGetBar()
    {
        $this->foo->setBar('logan');
        $this->assertEquals('logan', $this->foo->getBar());
    }
}