PHPUnit Mock Function Call - php

Question

I have the following function within an object that I wish to test
public function getUser($credentials, UserProviderInterface $userProvider)
{
$resourceOwner = $this->getAuthClient()->fetchUserFromToken($credentials);
// ... Code to create user if non-existent, update values, etc.
// ... Basically the code I want to test is here
return $user;
}
The getAuthClient() call returns a Client object with the available function of fetchUserFromToken
How can I, in a PHPUnit test, mock the fetchUserFromToken to just return a ResourceOwner object? Because the actual function does a lot of authentication mechanisms and is out of the scope of this test case

Answer 1

I found a php library called Runkit, but that is not the approach I want to peruse. It feels hacky and overkill for the problem at hand.
The getAuthClient() function is defined as follows
private function getAuthClient() {
return $this->clients->getClient('auth');
}
With $this->clients being defined by the constructor
public function __construct(ClientRepo $clients) {
$this->clients = $clients;
}
So, I mocked the ClientRepo and exposed the getClient() method to return a Mock of the AuthClient (regardless of input) so that I can control the return of fetchUserFromToken() call.
public function testGetUser() {
$client = $this->createMock(WebdevClient::class);
$client->expects($this->any())
->method('fetchUserFromToken')
->will($this->returnCallback(function()
{
// TARGET CODE
}));
$clients = $this->createMock(ClientRegistry::class);
$clients->expects($this->any())
->method('getClient')
->will($this->returnCallback(function() use ($client)
{
return $client;
}));
$object = new TargetObject($clients);
$result = $object->getUser(...);
// ... Assertions to follow
}