Testing defines in PHPUnit

This one tripped me up recently. Say you are wanting to test a bit of code using PHPunit that relies on a defined constant. You don’t want the define() to affect your other tests, you only want it to apply for this specific test. Something like this:

class MyTest extends PHPUnit_Framework_TestCase
{
    public function testExample()
    {
        define( 'EXAMPLEDEFINE', true );
        $result = $this->functionThatReliesOnEXAMPLEDEFINE();
        $this->assertEquals( 'success', $result );
    }
}

At first I figured that @runInSeparateProcess would do the trick. However that didn’t work and after doing some reading I discovered that @preserveGlobalState was also required.

class MyTest extends PHPUnit_Framework_TestCase
{
    /**
     * @preserveGlobalState disabled
     * @runInSeparateProcess
     */
    public function testExample()
    {
        define( 'EXAMPLEDEFINE', true );
        $result = $this->functionThatReliesOnEXAMPLEDEFINE();
        $this->assertEquals( 'success', $result );
    }
}

This worked for me and hopefully will save someone else some time in the future.