Symfony Doctrine relationship empty in PhpUnit test - php

Question

I have a Symfony app with a User entity with a many-to-many relation to a Cat entity. I also have a PhpUnit test which checks that deleting a cat (that belongs to 2 users) from 1 user doesn't actually delete the cat:
public function testDeletingACatBelongingToTwoUsersOnlyDeletesTheAssociationNotTheCat()
{
$cat = $this->createCat();
// Associate with user 1
$user1 = new User();
$user1->setEmail('test#example.com');
$user1->setPassword('pwdpwd');
$user1->addCat($cat);
$this->em->persist($user1);
// Associate with user 2
$user2 = new User();
$user2->setEmail('another#example.com');
$user2->setPassword('pwdpwd');
$user2->addCat($cat);
$this->em->persist($user2);
$this->em->flush();
// Sanity check:
$this->assertCount(1, $user1->getCats()); // PASS
$this->assertCount(1, $user2->getCats()); // PASS
$this->assertCount(2, $cat->getUsers()); // FAIL (0)
// ... perform the test (not shown here)
}
private function createCat(): Cat
{
$cat = new Cat();
$cat->setName($this->name);
$this->em->persist($cat);
$this->em->flush();
return $cat;
}
My question is, why does $cat->getUsers() return 0 in my test? At runtime it doesn't, it returns the correct value. It's only in the test that it returns 0.
Here are the relevant excerpts from my entities, auto-generated by Symfony:
/**
* #ORM\Entity(repositoryClass=UserRepository::class)
*/
class User implements UserInterface
{
/**
* #ORM\ManyToMany(targetEntity=Cat::class, inversedBy="users")
*/
private $cats;
/**
* #return Collection|Cat[]
*/
public function getCats(): Collection
{
return $this->cats;
}
public function addCat(Cat $cat): self
{
if (!$this->cats->contains($cat)) {
$this->cats[] = $cat;
}
return $this;
}
public function removeCat(Cat $cat): self
{
$this->cats->removeElement($cat);
return $this;
}
}
/**
* #ORM\Entity(repositoryClass=CatRepository::class)
*/
class Cat
{
/**
* #ORM\ManyToMany(targetEntity=User::class, mappedBy="cats")
*/
private $users;
/**
* #return Collection|User[]
*/
public function getUsers(): Collection
{
return $this->users;
}
}

Answer 1

The reason is, that collections are not synchronized with the database and synchronization between owning and inverse side is not automatically done either.
The category entries of your user entity probably will be persisted to the database (although I'm missing some cascade statements, but what do I know). When the category is created, it's collection of users is empty (obviously), then users add the category to the many-to-many relation in database.
BUT, the collection is a plain collection. If you loaded the category from the database, it would be a lazy-loaded PersistentCollection (or something alike), which would - only at the moment of access - fetch the items from the database (definition of lazy loading). Your test code has the plain collection (since you created the object yourself).
Not quite sure, if it'll work, but you could try refreshing the cat ($em->refresh($cat);) I'm not quite certain though, if that will replace the collection. Alternatively, you could make your User::addCat that it also calls $cat->addUser($this) (which you might have to add, beware the infinite recursion, which already should be prevented by the "contains" checks.).