Unit (real unit test) of test laravel relationship

Question

Background

• Framework: laravel 9.x
• PHP 8.0
• Continuous integration (Travis CI etc)

I am working on a project that is legally very sensitive, so testing is vital.

Due to project requirements, the project requires 100% unit testing and code coverage. This is a project requirement, even if it is relatively pointless in a few % of the cases. Just to be clear: the relationships work as expected in the functional/feature testing, however... this is for Unit testing. Traditional, no dependencies (mocks etc) unit tests.

To be clear: this is an exercise in reaching 100% coverage NOT necessarily "good" testing. Adding a "testing ignore" line needs to be justified, so this "suboptimal test" is still the best option for the project.

Question

How is it possible to UNIT test the following function:

use Illuminate\Database\Eloquent\Model;

// declaration: normal laravel model 
class Product extends Model

    /**
     * @return BelongsTo
     */
    public function user(): BelongsTo
    {
        return $this->belongsTo(User::class);
    }

This needs to be a Unit test. This testing will be run without a database connection, preferably without any other classes (except for mocks).

Answer 1

You would unit test a relationship the same you would anything else. No mocks needed...

1. Setup your data;
2. Executing your function; and
3. Assert your results.

/** @test */
public function a_product_can_access_its_associated_user()
{
    //Setup
    $product = Product::factory()
                ->for(User::factory()->create())
                ->create();
    
    //Executing & Asserting
    $this->assertTrue($product->user()->exists());
}

For more information on creating models with relationships in Laravel, review their documentation here.