Q:

Test multiple class with same PHPUnit test case

I have very simple php interface:
interface HasFormattableNumber {
    function setNumber();
    function setFormat();
    function formatNumber();
}

Next, I have many classes implementing this interface. Unfortunately, these classes cannot have a common ancestor (possibly an abstract one which would implement these methods only once). The class basically looks like this: 
class A implements HasFormattableNumber {
    private $_number;
    private $_format;

    public function setNumber($n) {
        $this->_number = $n;
    }
    public function setFormat($f) {
        $this->_format = $f;
    }
    public function formatNumber() {
        return sprintf($this->_format, $this->_number);
    }
}

An unit test would look something like this:
class ATest extends \PHPUnit_Framework_TestCase {
    public function testShouldFormatNumber() {
        $a = new A();
        $a->setNumber(123);
        $a->setFormat("xx-%d");
        $this->assertEquals("xx-123", $a->formatNumber());
    }
}

Is it possible to somehow reuse this test case for all of interface implementations? I know I can copy&paste testShouldFormatNumber() to all of my unit tests, but I prefer keeping it in one place if possible.
Would php Traits help in any way? (I'm not using php 5.4 yet, however)

A:

You can make a basetest that looks like your ATest except you don't initialize the class A in it, but use a class variable that you will define in all your implementations. You place the file in a directory or with a name so that PHPUnit won't run it. Then in your tests you can inherit from it and create the object as a class variable in setUp().

