oop - "backup and restore operations for static class attributes" in PHP

Solution:

The idea is simply to restore the initial known state between tests. Static properties are essentially the same as global variables. Consider

class TestSubject
{
    public static $i = 0;
    public function __construct() { self::$i++; }
}
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Now assume you create new instances ofTestSubject in your test's setup method. Because static properties are shared between all instances of a class,TestSubject::i will increase each time you create a new instance. It won't be reset. It maintains it's state globally. This is unwanted with Unit-Tests because in order to write reliable tests, you need an isolated, reproducable and known state. Thus, protected members have to be reset between test cases, which you can enable in PHPUnit with the@backupStaticAttributes annotation.

Example:

/**
 * @backupStaticAttributes enabled
 */
class Test extends PHPUnit_Framework_TestCase
{
    public function testInitialValueOfStaticMemberIsZero()
    {
        $this->assertSame(0, TestSubject::$i);
    }
    /**
     * @depends testInitialValueOfStaticMemberIsZero
     */
    public function testCreatingInstancesIncreasesStaticMember()
    {
        new TestSubject();
        new TestSubject();
        new TestSubject();
        $this->assertSame(3, TestSubject::$i);
    }
    /**
     * @depends testCreatingInstancesIncreasesStaticMember
     */
    public function testStaticMembersAreResetBetweenTests()
    {
        $this->assertSame(0, TestSubject::$i);
    }
}
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If you remove the annotation, the third test will fail.