Mock example in PHP

<?php

use PHPUnit\Framework\TestCase;

class UserRepository {
    private $db;

    public function __construct(Database $db) {
        $this->db = $db;
    }

    public function getUserById($id) {
        return $this->db->findUserById($id);
    }
}

class Database {
    public function findUserById($id) {
        return null;
    }
}

class UserRepositoryTest extends TestCase {

    public function testGetUserByIdCallsFindUserByIdOnce() {
        // Create a mock for the Database class
        $dbMock = $this->createMock(Database::class);

        // Set up the mock to expect findUserById to be called with 1 as parameter
        $dbMock->expects($this->once())
               ->method('findUserById')
               ->with($this->equalTo(1))
               ->willReturn(['id' => 1, 'name' => 'John Doe']);

        // Inject the mock into the UserRepository
        $userRepository = new UserRepository($dbMock);

        // Call the method
        $result = $userRepository->getUserById(1);

        // Assert the result
        $this->assertEquals(['id' => 1, 'name' => 'John Doe'], $result);
    }
}