Using laravel's HTTP tests, test the CustomerController's store method, make sure to mock the mailable "WelcomeNewCustomer" using mail-fake.

CustomerStoreTest.php

<?php

namespace Tests\Unit;

use PHPUnit\Framework\TestCase;
use Illuminate\Support\Facades\Mail;

class CustomerStoreTest extends TestCase
{
    public function test_customer_can_be_stored()
    {
        Mail::fake();

        $customerData = [
            'name' => 'Mark Berlon A. Pating',
            'email' => 'mbpating@gmail.com'
        ];

        $this->json('POST','/customer',$customerData,['Accept' => 'application/json'])
            ->assertStatus(201)
            ->assertJsonStructure([
                'saved' => true
            ]);
    }
}