Use case interactor

Question

Here is a class that executes the CreateAPerson use case. It takes a request object (which is a simple data structure), validates the request, creates a new person, and then returns a response object (another simple data structure).

For testability, I've created a setter that allows me to inject a mocked entity manager (I'm using Doctrine for persistence).

I realize this is rather simple, but do you see any red flags on the testability of this code?

<?php

namespace Stratus\UseCase\CreateAPerson;

class Interactor
{
    protected $entityManager;

    function __construct()
    {
        $doctrine = new \Stratus\Repository\Doctrine();
        $this->entityManager = $doctrine->getManager();
    }

    public function execute(Request $request)
    {
        if (!$request->isValid())
            throw new \Stratus\Exception\InvalidRequestException('Request did not pass validation.');

        $person = new \Stratus\Entity\Person();
        $person->setFirstName($request->firstName);

        $this->entityManager->persist($person);

        $response = new Response();
        $response->id = $person->getID();

        return $response;
    }

    public function setEntityManager($entityManager)
    {
        $this->entityManager = $entityManager;
    }
}

Answer 1

Constructor injection

Use constructor injection becouse this is the best way to write well readable and testable code. If you don't need a Doctrine instance in your class then don't use it.

public function __construct($entityManager)
    {
        $this->setEntityManager($entityManager);
    }