Laravel Passport API Problem

APITest.php

<?php

namespace Tests\Feature\Feature;

use App\User;
use Illuminate\Support\Facades\DB;
use Tests\TestCase;
use Illuminate\Foundation\Testing\WithFaker;
use Illuminate\Foundation\Testing\RefreshDatabase;

class APITest extends TestCase
{
    protected $access_tokens;
    /**
     * A basic test example.
     *
     * @return void
     */
    public function testAPI()
    {
        $this->artisan('migrate:fresh');
        $this->artisan('passport:install');

        factory(User::class, 5)->create([
            'password' => bcrypt('test12345')
        ]);

        $secret = DB::table('oauth_clients')->where('id', 2)->value('secret');

        $u1 = User::find(1);
        $u2 = User::find(2);

        $this->access_tokens['u1'] = $this->getTokenForUser($u1, $secret);
        $this->access_tokens['u2'] = $this->getTokenForUser($u2, $secret);

        dump($this->access_tokens);

        $u1_response = $this->withHeaders($this->headersWithToken($this->access_tokens['u1']))
            ->json('GET','api/user')
            ->assertStatus(200)
            ->decodeResponseJson();

        dump($u1_response);

        $u2_response = $this->withHeaders($this->headersWithToken($this->access_tokens['u2']))
            ->json('GET','api/user')
            ->assertStatus(200)
            ->decodeResponseJson();

        dump($u2_response);

        $fail_response = $this->withHeaders($this->headersWithToken('this_is_not_a_real_token'))
            ->json('GET','api/user')
            ->assertStatus(200)
            ->decodeResponseJson();

        dump($fail_response);

    }


    private function headersWithToken($token)
    {
        $headers = [
            "Accept" => 'application/json',
            "Authorization" => "Bearer " . $token,
            'X-Spa-Host' => "test_domain.com"
        ];
        return $headers;
    }

    private function getTokenForUser(User $user, $secret) {

        $postData = [
            "grant_type" => "password",
            "client_id" => 2,
            "client_secret" => $secret,
            "username" => $user->email,
            "password" => 'test12345',
            "scope" => ""
        ];

        $response = $this->json('POST', '/oauth/token', $postData)
            ->decodeResponseJson();

        $access_token = $response['access_token'];

        return $access_token;
    }

}