unit testing datastores in PHP - php

Question

I'm using PHPUnit but find it difficult to make it create good mocks and stubs for objects used as datastore.
Example:
class urlDisplayer {
private $storage;
public function __construct(IUrlStorage $storage) { $this->storage = $storage; }
public function displayUrl($name) {}
public function displayLatestUrls($count) {}
}
interface IUrlStorage {
public function addUrl($name, $url);
public function getUrl($name);
}
class MysqlUrlStorage implements IUrlStorage {
// saves and retrieves from database
}
class NonPersistentStorage implements IUrlStorage {
// just stores for this request
}
Eg how to have PHPUnit stubs returning more than one possible value on two calls with different $names?
Edit: example test:
public function testUrlDisplayerDisplaysLatestUrls {
// get mock storage and have it return latest x urls so I can test whether
// UrlDisplayer really shows the latest x
}
In this test the mock should return a number of urls, however in the documentation I only how to return one value.

Answer 1

Your question is not very clear - but I assume you are asking how to use phpunit's mock objects to return a different value in different situations?
PHPUnit's mock classes allow you specify a custom function (ie: a callback function/method) - which is practically unlimited in what it can do.
In the below example, I created a mock IUrlStorage class that will return the next url in its storage each time it is called.
public function setUp()
{
parent::setUp();
$this->fixture = new UrlDisplayer(); //change this to however you create your object
//Create a list of expected URLs for testing across all test cases
$this->expectedUrls = array(
'key1' => 'http://www.example.com/url1/'
, 'key2' => 'http://www.example.net/url2/'
, 'key3' => 'http://www.example.com/url3/'
);
}
public function testUrlDisplayerDisplaysLatestUrls {
//Init
$mockStorage = $this->getMock('IUrlStorage');
$mockStorage->expects($this->any())
->method('getUrl')
->will( $this->returnCallback(array($this, 'mockgetUrl')) );
reset($this->expectedUrls); //reset array before testing
//Actual Tests
$this->assertGreaterThan(0, count($this->expectedUrls));
foreach ( $this->expectedUrls as $key => $expected ) {
$actual = $this->fixture->displayUrl($key);
$this->assertEquals($expected, $actual);
}
}
public function mockGetUrl($name)
{
$value = current($this->expectedUrls);
next($this->expectedUrls);
//Return null instead of false when end of array is reached
return ($value === false) ? null : $value;
}
Alternatively, sometimes it is easier to simply create a real class that mocks up the necessary functionality. This is especially easy with well defined and small interfaces.
In this specific case, I would suggest using the below class instead:
class MockStorage implements IUrlStorage
{
protected $urls = array();
public function addUrl($name, $url)
{
$this->urls[$name] = $url;
}
public function getUrl($name)
{
if ( isset($this->urls[$name]) ) {
return $this->urls[$name];
}
return null;
}
}
?>
Then in your unit test class you simply instantiate your fixture like below:
public function setUp() {
$mockStorage = new MockStorage();
//Add as many expected URLs you want to test for
$mockStorage->addUrl('name1', 'http://example.com');
//etc...
$this->fixture = new UrlDisplayer($mockStorage);
}