SUT父级使用get_class检查依赖项

Question

It started when I was performing null checks everywhere to make sure I have the necessary entities for my interactor. Fortunately, I came across this post which points towards not allowing the entities to be in an invalid state do the check in your constructor. Now my Interactors use protected static $request to state explicitly which entities they require, which are then passed in during instantiation. I chose static so the check could be done prior to creating an instance of the Interactor.

abstract class Interactor {
  protected static $request = [];
  protected $entities = [];

  final public function __construct(Entity ...$entities) {
    $this->setEntities(...$entities);
    $this->checkEntities();
  }

  final private function setEntities(Entity ...$entities) {
    foreach($entities as $entity) {
      $this->setEntity($entity);
    }
  }
  final private function setEntity(Entity $entity){
    $className = get_class($entity);

    if (!in_array($className, static::$request)){
      throw new Exception("Not a requested entity");
    }
    $this->entities[$className] = $entity;
  }
  final private function checkEntities(){
    if (count(static::$request) != count($this->entities))
      throw new Exception("Entity mismatch");

    foreach(static::$request as $index=>$name) {
      if (!array_key_exists($name, $this->entities))
        throw new Exception("Missing requested entity ($name)");
      if (!is_a($this->entities[$name], $name))
        throw new Exception("Not the specified entity");
    }
  }

  final public static function getRequest(){
    return array_values(static::$request);
  }
}

Ok great, now I just do the check in a single location and I don't need to worry about performing null checks at the beginning of my functions. The problem with the way I am going about it now is that my Interactor is checking the class name against a static class name request array. Thus, when I DI the mocked entities during testing, my parent Interactor throws an exception saying it isn't in the pre approved list.

To demonstrate is the following simplified Chess example:

class Chess extends Interactor {
  protected static $request = ['Piece','Engine','Board'];
}

Then we have our Entities:

abstract class Entity {}
class Piece extends Entity {}
class Engine extends Entity {}
class Board extends Entity {}

And finally our test:

class ChessTest extends TestCase {
  function setUp(){
    $this->piece = $this->getMockBuilder(Piece::class)->getMock();
    $this->engine = $this->getMockBuilder(Engine::class)->getMock();
    $this->board = $this->getMockBuilder(Board::class)->getMock();

    $this->chess = new Chess($this->piece, $this->engine, $this->board);
  }
  function testCanSetup(){
    $this->assertTrue(
      is_a($this->chess, Chess::class)
    );
  }
}

Which throws Exception: Interactor receiving entity not requested (Mock_Piece_faaf8b14)

Of course Mock_Piece_faaf8b14 is not going to be in our static::$request array, so this is destined to throw an exception.

The workaround I have come up with so far is to include in Entity:

public function getClassName(){
  return get_called_class();
}

Then in Interactor->setEntity($entity) instead of using get_class($entity) I would use $entity->getClassName() which then becomes trivial to mock.

I thought the way I had created the Interactor was inline with what the previously mentioned post was getting at, only take the entities in the constructor. However, it all feel apart when I injected mocked entities.

1) Is there a way to avoid getClassName() in my entities?

2) Is there something in the entities I can mock that gets called in get_class() instead?

Thank you for your help!

Answer 1

You are checking to see if the name of your class is one of the keys in your $request array. And it isn't. The keys in your array are numerical 0, 1, 2 so you are throwing the exception. I think that you want to use in_array instead.

Though at the same time, this still wouldn't pass with the mock because you are checking to see if the class name is in $request. So the name won't be there at all either and the exception will still be thrown.

If all that your Interactor class is doing is making sure that the correct objects are passed into the constructor why not just use PHP's native type hinting?

Your Chess class becomes:

class Chess {
    public function __construct(Piece $piece, Engine $engine, Board $board) { }
}

PHP will make sure that the passed in objects are of the correct type and will allow you to mock them for testing.

You get the type checking that you are looking for without need to use getClassName() at all.