phpUnitでLaravelの初期認証ログインのテストができない

前提・実現したいこと

Laravel内のphpunitを利用して単体テストを実装中。
認証処理についてはLaravelの初期にあるものをいじっていない状態です。

投稿主の認識ですとemailとpasswordがあれば通る認識ですが通らず。
Laravel初学者であるため、こちらの原因についてご指摘いただけると幸いです。

発生している問題・エラーメッセージ

Illuminate\Validation\ValidationException: The given data was invalid.

該当のソースコード

<?php

namespace App\Http\Controllers\Auth;

use App\Http\Controllers\Controller;
use App\Providers\RouteServiceProvider;
use Illuminate\Foundation\Auth\AuthenticatesUsers;

use Illuminate\Http\Request;

class LoginController extends Controller
{
    /*
    |--------------------------------------------------------------------------
    | Login Controller
    |--------------------------------------------------------------------------
    |
    | This controller handles authenticating users for the application and
    | redirecting them to your home screen. The controller uses a trait
    | to conveniently provide its functionality to your applications.
    |
    */

    use AuthenticatesUsers;

    /**
     * Where to redirect users after login.
     *
     * @var string
     */
    protected $redirectTo = RouteServiceProvider::HOME;

    /**
     * Create a new controller instance.
     *
     * @return void
     */
    public function __construct()
    {
        $this->middleware('guest')->except('logout');
    }

    /**
     * The user has been authenticated.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  mixed  $user
     * @return mixed
     */
    protected function authenticated(Request $request, $user)
    {
        return $user;
    }
}

//AuthTest.php
<?php

namespace Tests\Feature;

use App\User;
use Illuminate\Foundation\Testing\RefreshDatabase;
use Illuminate\Foundation\Testing\WithFaker;
use Tests\TestCase;
use Illuminate\Foundation\Testing\DatabaseTransactions;
use Illuminate\Foundation\Testing\WithoutMiddleware;


class AuthTest extends TestCase
{
    /**
     * A basic feature test example.
     *
     * @return void
     */

    use DatabaseTransactions;
    use WithoutMiddleware;

    public function testLogin()
    {
        $this->withoutExceptionHandling();

        $user = factory(User::class)->create([
                "email" =>"test@gmail.com",
                "password" => "p@ssw0rd0"
        ]);

        $response = $this->post('/api/login',["email" =>"test@gmail.com","password" => "p@ssw0rd0"]);

        $response->assertStatus(200);
    }

    // public function testLogout()
    // {
    //     $response = $this->get('/');
    //     $response->assertStatus(200);
    // }
}

<?php

/** @var \Illuminate\Database\Eloquent\Factory $factory */

use App\User;
use Faker\Generator as Faker;
use Illuminate\Support\Str;

/*
|--------------------------------------------------------------------------
| Model Factories
|--------------------------------------------------------------------------
|
| This directory should contain each of the model factory definitions for
| your application. Factories provide a convenient way to generate new
| model instances for testing / seeding your application's database.
|
*/

$factory->define(User::class, function (Faker $faker) {
    return [
        'name' => $faker->name,
        'email' => $faker->unique()->safeEmail,
        'email_verified_at' => now(),
        'password' => 'p@ssw0rd', // password
        'remember_token' => Str::random(10),
    ];
});