What should be tested (TDD) in simple entities?

I am learning code testing (TDD) and wondering what should be tested for simple entities in Symfony?

From official documentation:

namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * Category
 *
 * @ORM\Table(name="category")
 * @ORM\Entity(repositoryClass="AppBundle\Repository\CategoryRepository")
 */
class Category
{
    /**
     * @ORM\Column(name="id", type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\Column(name="name", type="string", length=255)
     */
    private $name;

    /**
     * @ORM\OneToMany(targetEntity="Product", mappedBy="category")
     */
    private $products;
    /**
     * Constructor
     */
    public function __construct()
    {
        $this->products = new \Doctrine\Common\Collections\ArrayCollection();
    }

    /**
     * Get id
     *
     * @return integer
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set name
     *
     * @param string $name
     *
     * @return Category
     */
    public function setName($name)
    {
        $this->name = $name;

        return $this;
    }

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

    /**
     * Add product
     *
     * @param \AppBundle\Entity\Product $product
     *
     * @return Category
     */
    public function addProduct(\AppBundle\Entity\Product $product)
    {
        $this->products[] = $product;

        return $this;
    }

    /**
     * Remove product
     *
     * @param \AppBundle\Entity\Product $product
     */
    public function removeProduct(\AppBundle\Entity\Product $product)
    {
        $this->products->removeElement($product);
    }

    /**
     * Get products
     *
     * @return \Doctrine\Common\Collections\Collection
     */
    public function getProducts()
    {
        return $this->products;
    }
}

Second:

namespace AppBundle\Entity;

use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity
 * @ORM\Table(name="product")
 */
class Product
{
    /**
     * @ORM\Column(type="integer")
     * @ORM\Id
     * @ORM\GeneratedValue(strategy="AUTO")
     */
    private $id;

    /**
     * @ORM\Column(type="string", length=100)
     */
    private $name;

    /**
     * @ORM\Column(type="decimal", scale=2)
     */
    private $price;

    /**
     * @ORM\Column(type="text")
     */
    private $description;

    /**
     * @ORM\ManyToOne(targetEntity="Category", inversedBy="products")
     * @ORM\JoinColumn(name="category_id", referencedColumnName="id")
     */
    private $category;

    /**
     * Get id
     *
     * @return integer
     */
    public function getId()
    {
        return $this->id;
    }

    /**
     * Set name
     *
     * @param string $name
     *
     * @return Product
     */
    public function setName($name)
    {
        $this->name = $name;

        return $this;
    }

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

    /**
     * Set price
     *
     * @param string $price
     *
     * @return Product
     */
    public function setPrice($price)
    {
        $this->price = $price;

        return $this;
    }

    /**
     * Get price
     *
     * @return string
     */
    public function getPrice()
    {
        return $this->price;
    }

    /**
     * Set description
     *
     * @param string $description
     *
     * @return Product
     */
    public function setDescription($description)
    {
        $this->description = $description;

        return $this;
    }

    /**
     * Get description
     *
     * @return string
     */
    public function getDescription()
    {
        return $this->description;
    }

    /**
     * Set category
     *
     * @param \AppBundle\Entity\Category $category
     *
     * @return Product
     */
    public function setCategory(\AppBundle\Entity\Category $category = null)
    {
        $this->category = $category;

        return $this;
    }

    /**
     * Get category
     *
     * @return \AppBundle\Entity\Category
     */
    public function getCategory()
    {
        return $this->category;
    }
}

I thought I had to create an Entity folder and within CategoryTest file:

namespace Tests\AppBundle\Entity;

use AppBundle\Entity\Tag;
use AppBundle\Form\DataTransformer\TagArrayToStringTransformer;
use Doctrine\Common\Persistence\ObjectManager;
use Doctrine\ORM\EntityRepository;

class CategoryTest extends \PHPUnit\Framework\TestCase
{
    public function testGetName()
    {
        $category = new \AppBundle\Entity\Category();
        $category->setName('test');
        $this->assertSame('test', $category->getName());
    }
}

So... In TDD I should testing all fields? For Product entity I should testing name, price and description?

If yes, how to deal with refactoring? In these cases I must use in all methods "$product = new Product();";

For a name field I might need to do another test? What?

Should I also test relationships or do it in functional tests?