Testing (PHPUnit) databases in Laravel - completely confused about the setup - how to figure it out?

Question

PHPUnit

For some reason, the Laravel documentation https://laravel.com/docs/8.x/database-testing assumes that I've only been doing database testing for two years now. But it's not. The topic of testing is quite fresh for me. So I don't understand at all:

1. Why should I do "Resetting The Database After Each Test"?

2. Why do I need to specify 'sqlite' and ':memory:' in phpunit.xml settings?

Even in version 5.4 there is such a feature:

use Illuminate\Foundation\Testing\DatabaseMigrations;
use Illuminate\Foundation\Testing\DatabaseTransactions;

this also applies to paragraph 1.

Can someone simply and clearly explain in two sentences why all this is needed at all?

Answer 1

In general, it turns out that the guide writers are too clever again :)
It is quite enough to put the line in the class definition: Then the records in the database are simply rolled back - in the DatabaseTransactions trait this is implemented through a hook: you can do without other frills. In addition to this, you can use another copy of the main database purely for testing purposes.
use DatabaseTransactions;
beforeApplicationDestroyed()