How to mock a Doctrine Repository in Zend Framework 3 using PHPUnit - doctrine-orm

Question

I am trying to test a ZF3 controller action which, in the process, selects a user from the database via a Doctrine ORM repository using a token given as a GET-Parameter. As I need to make sure that the User exists I need to create a mock of the repository returning the user object. How do I do this?
My setup is the following:
The class UserControllerFactory is instantiating a UserController class:
class UserControllerFactory implements FactoryInterface {
/**
* #param ContainerInterface $container Zend\ServiceManager\ServiceManager
* #param string $requestedName
* #param array|NULL $options
*
* #return UserController
*/
public function __invoke(ContainerInterface $container, $requestedName, Array $options = NULL) {
$entityManager = $container->get('doctrine.entitymanager.orm_default');
$userRepository = $entityManager->getRepository('User\Entity\User');
return new UserController($container, $entityManager, $userRepository);
}}
In the UserController the acton resetPassword is called. It gets the needed parameter from the route and selects a user from the database matching the token:
public function resetPasswordAction() {
$request = $this->getRequest();
$passwordResetToken = $this->params()->fromRoute('token');
if(strlen(trim($passwordResetToken))) {
$user = $this->userRepository->findOneBy(
[
'passwordResetToken' => $passwordResetToken
]
);
...
If no user is found. The action will redirect to user to a different action.
PHPUnit test case:
public function testResetPasswordActionCanBeAccessed() {
$passwordResetToken = 'testToken1234';
$this->dispatch("/user/resetPassword/$passwordResetToken", 'GET');
$this->assertNotRedirect();
}
As there is no user having the token is will be redirected.
To my knowledge I need to create a mock of the repository (userRepository), create a mock user and use the mock repository retrieve the mock user having the token.
I am not sure if this is the right approche as I tried a lot of tutorial and never got it to work. I don't know how to "replace" the, in the action called "userRepository" with the in the unit test created mock object.
I am happy to provide more details if needed.
EDIT
As suggested by #DonCallisto (thank you) I changed my test case code to:
...
$mockedEm = $this->createMock(EntityManager::class);
$mockedUserRepository = $this->createMock('Core\Repository\EntityRepository');
$mockedEm->method('getRepository')->willReturn($mockedUserRepository);
$mockedUserRepository->method('findOneBy')->willReturn($mockedUser);
$this->dispatch("/$this->_lang/user/resetPassword/$passwordResetToken", 'GET');
...
but after calling the "dispatch" in the test case my controller call
$user = $this->userRepository->findOneBy(...)
will still return NULL instead of the mocked user object given in the test. If I debug the $mockedUserRepository, my $mockedUser is assigned correctly.
I also tried the suggested:
$mockedUserRepository->findOneBy([arrayWithParams])->willReturn($mockedUser);
But this will through an error due to the fact that $mockedUserRepository->findOneBy() is returning NULL.