Question

I’m implementing unit testing with PHPUnit on an existing codebase. I’m fairly new to unit testing, but I understand that a goal is to completely isolate the code one is testing. This is proving difficult with my codebase because many of the classes depend on other classes in the codebase.

The dependencies are hard coded into the classes, so there’s no way to use dependency injection. I also don’t want to refactor the existing code just for the sake of testing it.
So in order to isolate each class from it’s dependencies, I’ve created a library of “mock” classes (not by using PHPUnit’s mocking framework, but by literally creating a library of classes that contain stub functions that return what I expect based on specific input).

The problem is that if, during a run of phpunit, I have a test that calls the mock class, and then I try to test the actual class, I get a fatal error because PHP sees this as redeclaring the class. Here is a simplified example of what I mean. Note that this still fails even if I unset all instances of the classes I’ve included and clear the include path in a tearDown method. Again, I’m new to unit testing, so if I’m going about this the wrong way or missing something obvious, please let me know.

A bigger question could be if this approach is going to far in the direction of isolating code, and if it’s actually a benefit to use real objects as my class’ dependencies.

#### real A

require_once 'b.class.php';

class A {   
    private $b;

    public function __construct() {
        $this->b = new B();
    }

    public function myMethod($foo) {
        return $this->b->exampleMethod($foo);
    }
}


#### real B

class B {
    public function exampleMethod($foo) {
        return $foo . "bar";
    }
}


#### mock B

class B {
    public function exampleMethod($foo) {
        switch($foo) {
            case 'test':
                return 'testbar';
            default:
                throw new Exception('Unexpected input for stub function ' . __FUNCTION__);
        }
    }
}


#### test A

class TestA extends PHPUnit_Extensions_Database_TestCase {
    protected function setUp() 
    {
        // include mocks specific to this test
        set_include_path(get_include_path() . PATH_SEPARATOR . 'tests/A/mocks');

        // require the class we are testing
        require_once 'a.class.php';     

        $this->a = new A();
    }

    public function testMyMethod() {
        $this->assertEquals('testbar', $a->myMethod('test'));
    }
}

#### test B

class TestB extends PHPUnit_Extensions_Database_TestCase {
    protected function setUp()
    {
        // include mocks specific to this test
        set_include_path(get_include_path() . PATH_SEPARATOR . 'tests/B/mocks');

        // require the class we are testing
        // THIS FAILS WITH: 'PHP Fatal error:  Cannot redeclare class B'
        require_once 'b.class.php';

        $this->b = new AB();
    }   
}

Answer 1

I think you need to run your tests in isolated processes

Either you give an argument for executing your test: “–process-isolation” or you set $this->processIsolation = true;