Employee.php

<?php
/**
 * Created by PhpStorm.
 * User: ravibastola
 * Date: 9/16/18
 * Time: 11:09 PM.
 */

namespace App;

class Employee
{
    /**
     * @var string
     */
    protected $name;

    /**
     * Employee constructor.
     *
     * @param $address
     */
    public function __construct($name)
    {
        $this->name = $name;
    }

    /**
     * @return string
     */
    public function getName()
    {
        return $this->name;
    }
}

EmployeeRepository.php

<?php
/**
 * Created by PhpStorm.
 * User: ravibastola
 * Date: 9/16/18
 * Time: 11:09 PM.
 */

namespace App;

class EmployeeRepository
{
    private $dbConnection;

    public function __construct($dbConnection)
    {
        $this->dbConnection = new \mysqli('localhost', 'root', '', 'office');
    }

    /**
     * @param $address
     * @return array
     * @throws \Exception
     */
    public function findByAddress($address)
    {
        $sql = 'SELECT * FROM employees WHERE address = ?';
        $stmt = $this->dbConnection->prepare($sql);

        if (!$stmt) {
            throw new \Exception($this->dbConnection->getError());
        }

        $stmt->bind_param('s', $address);

        if (!$stmt->execute()) {
            return [];
        }

        $result = $stmt->get_result();
        $employeeName = [];
        while ($data = $result->fetch_assoc()) {
            $employeeName[] = new Employee($data['name']);
        }
        $result->free();

        return $employeeName;
    }
}

EmployeeRepositoryTest.php

<?php

use App\EmployeeRepository;
use PHPUnit\Framework\TestCase;

/**
 * Created by PhpStorm.
 * User: ravibastola
 * Date: 9/16/18
 * Time: 11:05 PM.
 */
class EmployeeRepositoryTest extends TestCase
{
    private $employeeRepository;
    private $databaseMock;

    public function setUp()
    {
        parent::setUp();
        $this->databaseMock = Mockery::mock(mysqli::class);
        $this->employeeRepository = new EmployeeRepository($this->databaseMock);
    }

    /**
     * @test
     */
    public function it_finds_the_employees_by_given_address()
    {
        $result = Mockery::spy('mysqli_result_mock')->shouldIgnoreMissing();

        $result->shouldReceive('fetch_assoc')
            ->andReturn(['name' => 'John Doe'], null);

        $statement = Mockery::spy('mysqli_stmt_mock');

        $statement->shouldReceive('bind_param')
            ->with('s', 'Kathmandu');

        $statement->shouldReceive('execute')
            ->andReturn(true);

        $statement->shouldReceive('get_result')
            ->andReturn($result);

        $this->databaseMock->shouldReceive('prepare')
            ->with('SELECT * FROM employees WHERE address = ?')
            ->andReturn($statement);

        $employeeName = $this->employeeRepository->findByAddress('Kathmandu');

        $this->assertInstanceOf(\App\Employee::class, $employeeName[0]);
        $this->assertSame('John Doe', $employeeName[0]->getName());
    }
}