Тест для entity Tags (он без relation) писал так:
<?php
use App\Ext\Shop\Entity\Tags;
use Codeception\Test\Unit;
class TagsTest extends Unit
{
public function testBuildResponse()
{
$params = [
'id' => 1,
'code' => 'TestCode',
];
$entity = new Tags();
$this->setPrivateProperty($entity, 'id', $params['id']);
$entity->setCode($params['code']);
$this->assertEquals($params['code'], $entity->getCode());
$this->assertEquals($params['id'], $entity->getId());
}
private function setPrivateProperty($entity, $property, $value)
{
$rp = new ReflectionProperty($entity, $property);
$rp->setAccessible(true);
$rp->setValue($entity, $value);
}
}