Test data builder

examples.php

<?php

$defaultUser = (new  UserBuilder())->build();

$justRegisteredUser = UserBuilder::justRegistered()->withUsername('Anonymous')->build();

$complexUser = (new UserBuilder())
    ->withUsername('Test user')
    ->withEmail('test@example.com')
    ->build();
    
$user = (new UserBuilder())
    ->with(['username' => 'Test user'])
    ->build();

TestDataBuilder.php

<?php

namespace Acme\Builder;

class TestDataBuilder
{
    /**
     * @var array
     */
    protected $defauts = [];

    /**
     * @var array
     */
    protected $data = [];

    /**
     * @return object
     */
    public function build()
    {
        $data = array_merge($this->defaults, $this->data);

        $entity = $this->instantiate();

        foreach ($data as $field => $value) {
            $this->setObjectProperty($entity, $field, $value);
        }

        return $entity;
    }

    /**
     * @param string $name
     * @param array  $arguments
     *
     * @return $this
     *
     * @throws \BadMethodCallException in case method is not supported
     */
    public function __call($name, $arguments)
    {
        if (0 === strpos($name, 'with') && 1 === count($arguments)) {
            $name = lcfirst(str_replace('with', '', $name));
            
            return $this->withProperty($name, $arguments[0]);
        }

        throw new \BadMethodCallException(sprintf('Call to undefined method %s::%s', static::class, $name));
    }

    /**
     * @param array $data
     *
     * @return $this
     */
    public function with(array $data)
    {
        foreach ($data as $property => $value) {
            $this->data[$property] = $value;
        }

        return $this;
    }

    /**
     * @param string $name
     * @param mixed  $value
     *
     * @return $this
     */
    protected function withProperty($name, $value)
    {
        $this->data[$name] = $value;

        return $this;
    }

    /**
     * @param object $object
     * @param string $name
     * @param mixed  $value
     */
    protected function setObjectProperty($object, $name, $value)
    {
        $property = new \ReflectionProperty(static::DATA_CLASS, $name);
        $property->setAccessible(true);
        $property->setValue($object, $value);
    }

    /**
     * @return object
     *
     * @throws \RuntimeException in case the DATA_CLASS constant hasn't been set
     */
    protected function instantiate()
    {
        if (!defined('static::DATA_CLASS')) {
            throw new \RuntimeException(sprintf('Define DATA_CLASS constant for the %s', get_class($this)));
        }

        $class = static::DATA_CLASS;

        return new $class();
    }
}

UserBuilder.php

<?php

namespace Acme\Builder;

use Acme\User;

class UserBuilder extends TestDataBuilder
{
    const DATA_CLASS = User::class;

    protected $defaults = [
        'username' => 'Kuba',
        'email' => 'kuba@example.com',
        'registeredAt' => null,
        'active' => true
    ];
    
    public function __construct()
    {
        $this->defaults['registeredAt'] = new \DateTime('-1year');
    }
    
    static public function justRegistered()
    {
        return (new self())
            ->withRegisteredAt(new \DateTime('now'));
    }
    
    public function withRegisteredAt(\DateTime $registeredAt)
    {
        return $this->withProperty('registeredAt', $registeredAt);
    }
}

This is good stuff! Could you add a license to it? Otherwise it's difficult to use it in other projects. Thanks!