[Laravel8.x] Unitテスト基礎

単体テストがイマイチ腹に落ちない。
やりたいことは、controllerのメソッド単位でのテスト

$ php artisan make:test AdminTest
/tests/Feature/AdminTest.php

    public function testExample()
    {
        $response = $this->get('/');

        $response->assertStatus(200);
    }

$ vendor/bin/phpunit tests/Feature/AdminTest.php
PHPUnit 9.4.2 by Sebastian Bergmann and contributors.

. 1 / 1 (100%)

Time: 00:00.144, Memory: 26.00 MB

OK (1 test, 1 assertion)

route/web.php

Route::get('/admin/test/form', [App\Http\Controllers\AdminController::class, 'testForm']);

AdminController

    public function testForm(){
        return "hello";
        // return view('admin.test');
    }

    public function testExample()
    {
        $response =  $this->get('/admin/test/form');
        $response->assertSee("hello");
    }

$ vendor/bin/phpunit tests/Feature/AdminTest.php
PHPUnit 9.4.2 by Sebastian Bergmann and contributors.

. 1 / 1 (100%)

Time: 00:00.086, Memory: 26.00 MB

OK (1 test, 1 assertion)

なるほど、$response->assertSee(); で確認するのか。assertEqualsとかassertSameで確認してた。

$ vendor/bin/phpunit tests/Feature/AdminTest.php

use App\Models\User;
public function testExample()
    {
        // $response = $this->get('/');
        $response =  User::all(); 
        dd($response);
        
    }

$ vendor/bin/phpunit tests/Feature/AdminTest.php
PHPUnit 9.4.2 by Sebastian Bergmann and contributors.

Illuminate\Database\Eloquent\Collection^ {#1678
#items: []
}
なんでnullになるのか理解できん。
データベースのテストの方法が違うっぽいな。