Laravel 8 Tests: PHPUnit error: Unknown formatter "unique" - laravel

Question

I have written a test that involves a factory. When I execute the test, I get this error:
The data provider specified for Tests\Unit\ExampleTest::testTakePlace is invalid. InvalidArgumentException: Unknown formatter "unique" /var/www/html/api/vendor/fakerphp/faker/src/Faker/Generator.php:249
Expected result
This error should not be shown, I should be able to use $this->faker->unique().
How I tried to fix this problem
By reading the doc again and again (no difference was found) and by reading questions&answers on the Internet (only one question & only one answer were found: to extend Laravel's TestCase but the official documentation, as I mentionned it, says the contrary). (Laravel's TestCase is provided by use Illuminate\Foundation\Testing\TestCase;)
Question
Why doesn't it work and how to fix this bug?
Sources
Test sources
It extends PHPUnit\Framework\TestCase (not Laravel's TestCase) because the documentation says to extend it. Indeed: https://laravel.com/docs/8.x/testing#creating-and-running-tests . This is not the only part of the doc mentionning to extend it.
<?php
namespace Tests\Unit;
use PHPUnit\Framework\TestCase;
use App\Models\Project;
class ExampleTest extends TestCase
{
/**
* #dataProvider provideTakePlaceData
*/
public function testTakePlace($project)
{
$response = $this->json('GET', '/controllerUserProject_takePlace', [
'project_id' => $project->id
]);
}
public function provideTakePlaceData() {
return [
Project::factory()->make()
];
}
}
Controller
<?php
namespace App\Http\Controllers;
use App\Http\Controllers\Controller;
use Illuminate\Http\Request;
class ControllerUserProject extends Controller
{
public function takePlace(Request $request, $project_id)
{
return;
}
}
The most important: the factory
<?php
namespace Database\Factories;
use App\Models\Project;
use Illuminate\Database\Eloquent\Factories\Factory;
use Illuminate\Support\Str;
class ProjectFactory extends Factory
{
/**
* The name of the factory's corresponding model.
*
* #var string
*/
protected $model = Project::class;
/**
* Define the model's default state.
*
* #return array
*/
public function definition()
{
return [
'id' => $this->faker->unique()->numberBetween(1, 9000),
];
}
}

Answer 1

Change:
use PHPUnit\Framework\TestCase;
to:
use Tests\TestCase;
Why?
When your ExampleTest extends PHPUnit\Framework\TestCase Laravel app is never initialized in tests, and so you don't have access to Laravel features like factories.
The documentation tells you to extend PHPUnit\Framework\TestCase;, but it refers to Unit tests. Feature tests should extend Tests\TestCase. This is something pretty new. Until Laravel 5.8 both unit and feature tests were extending Tests\TestCase by default. I personally just define all tests as feature tests to avoid such issues.

Answer 2

The problem was due to the use of a dataProvider with the use of the factories. More precisely: PHPUnit data providers should not be used when Laravel factories are.

Answer 3

If you are using faker in Factories please make sure these are working correctly regardless (as per example try running Project::factory()->make(); within Laravel Tinker and see the results)
Second common issue (as mentioned above) is the class that you extend your Test with - see above
Third and frequently omitted one that's causing this error, is a missing parent constructor call in the setUp() - (if you use it)
<?php
namespace Tests\Unit;
use Tests\TestCase;
use App\Models\Project;
class ExampleTest extends TestCase
{
protected Project $project;
public function setUp(): void
{
parent::setUp();
$this->project = Project::factory()->make();
}

Answer 4

I think you need to use the WithFaker trait to use faker :
<?php
namespace Tests\Unit;
use PHPUnit\Framework\TestCase;
use App\Models\Project;
use Illuminate\Foundation\Testing\WithFaker;
class ExampleTest extends TestCase
{
use WithFaker;
// ...
}