Write tests in phpunit for Laravel json API

I have trouble in create tests for my API in laravel. Here how look my routes.php:

Route::group(['middleware' =>'api', 'prefix' => '/api/v1', 'namespace' => 'Api\V1'], function () {


    Route::post('/login', 'Auth\AuthController@postLogin');

    Route::group(['middleware' =>'jwt.auth'], function () {
        Route::post('/projects', 'ProjectsController@postProjects');
        ...
    });

});

My ProjectsController@postProjects looks like this (I test it by POSTman and it works fine):

public function postProjects() {
    $project = new Project;
    $project->fill(request()->all());
    $project->user_id = Auth::user()->id;
    $project->save();
    return ['project_id' => $project->id];
}

I write my own middelware for authentication using JWT cookie which is described in details here. But in my test, I try to turn off middelware (use WithoutMiddleware)and act as logged user (actingAs($user) - I have user (id=1) in my DB). My test looks like that (I wrote it using this documentation):

<?php

use Illuminate\Foundation\Testing\WithoutMiddleware;
use Illuminate\Foundation\Testing\DatabaseMigrations;
use Illuminate\Foundation\Testing\DatabaseTransactions;
use App\Models\User;

class ProjectsTest extends TestCase
{
    use WithoutMiddleware;

    /**
     * A basic functional test example.
     *
     * @return void
     */
    public function testBasicExample()
    {

        $user = User::find(1);

        $this->actingAs($user)
                ->json('POST', '/projects', ['name' => 'Project_test_name' ])
                ->seeJson([
                 'project_id' => 1,
             ]); // THIS IS LINE 26
    }
}

But I get the following error during execution of vendor/bin/phpunit:

Time: 182 ms, Memory: 13.75MB

There was 1 error:

1) ProjectsTest::testBasicExample ErrorException: Invalid argument supplied for foreach()

/Users/Kamil/Desktop/Code/kumarajiva.com/vendor/laravel/framework/src/Illuminate/Support/Arr.php:494 /Users/Kamil/Desktop/Code/kumarajiva.com/vendor/laravel/framework/src/Illuminate/Foundation/Testing/Concerns/MakesHttpRequests.php:232 /Users/Kamil/Desktop/Code/kumarajiva.com/vendor/laravel/framework/src/Illuminate/Foundation/Testing/Concerns/MakesHttpRequests.php:257 /Users/Kamil/Desktop/Code/kumarajiva.com/tests/ProjectsTest.php:26

FAILURES! Tests: 2, Assertions: 2, Errors: 1.

Any ideas what to do with this error?