Cache PDO in RefreshDatabase trait

[mzur]

This caches the PDO object in the RefreshDatabase trait for tests.

Originally, I implemented this for my own tests to fix the "too many connections" error which can occur if a database other than in-memory SQLite is used in the tests. But I noticed that this also substantially sped up my tests, too. I have 1152 feature tests and most of these use the database. With the default RefreshDatabase trait, these finish after an average 62 seconds. With the updated trait, the tests finish in an average 41 seconds, which is 65 % of the previous time!

This also may make the change from #22569 obsolete but I left the diconnect there because it had no noticable negative effect on the runtime.

[mzur]

Somebody please rerun the failed tests. The error is unrelated to my changes.

[taylorotwell]

This feels pretty risky to throw on a patch release. Feel free to add it to your own project if you find it helps.

[mzur]

Fair enough! If anyone is interested, this can be done directly in the TestCase class as well:

<?php

use App\Tests\CreatesApplication;
use Illuminate\Foundation\Testing\TestCase as BaseTestCase;
use Illuminate\Foundation\Testing\RefreshDatabase;

class TestCase extends BaseTestCase
{
    use CreatesApplication, RefreshDatabase;

    public static $cachedPdo;

    protected function beforeRefreshingDatabase()
    {
        if (static::$cachedPdo) {
            DB::setPdo(static::$cachedPdo);
        } else {
            static::$cachedPdo = DB::getPdo();
        }
    }
}