Sometimes, when we are testing, it would be very nice to just easily swap out the various Storage:disk() calls with a virtual files system like mikey179/vfsStream.

composer require stechstudio/laravel-vfs-adapter

Then register the provider in your App\Providers\AppServiceProvider like so:

public function register()
{
    if ($this->app->environment() === 'testing') {
        if (class_exists(VfsFilesystemServiceProvider::class)) {
            $this->app->register(VfsFilesystemServiceProvider::class);
        }
    }
}

This assumes you stick with the default APP_ENV=testing settings that Laravel comes with out of the box. Of course, you may also register the provider in the more traditional manner if you want the virtual file system adapter available in other environments, of it you just don't like the way we do it.

All configuration can be done in a combination of your .env, phpunit.xml, and config/filesystems.php.

Suppose you had a config/filesystems.php that looked something like this:

return [
    ....

    'disks' => [
        'data' => [
            'driver' => 'local',
            'root'   => env('STORAGE_DATA_DIR'),
        ],

        'archive' => [
            'driver'   => 's3'
            'key'      => env('S3_KEY'),
            'secret'   => env('S3_SECRET'),
            'region'   => env('S3_REGION'),
            'bucket'   => env('S3_DEVELOP_BUCKET')
        ]
    ],
];

Simply make a few modifications:

return [
    ....

    'disks' => [

        'data' => [
            'driver' => env('STORAGE_DATA_DRIVER', 'local'),
            'root'   => env('STORAGE_DATA_DIR'),
            'dir_name' => 'data'
        ],

        'archive' => [
            'driver'   => env('S3_ARCHIVE_DRIVER', 's3')
            'key'      => env('S3_KEY'),
            'secret'   => env('S3_SECRET'),
            'region'   => env('S3_REGION'),
            'bucket'   => env('S3_DEVELOP_BUCKET'),
            'dir_name' => 'archive'
        ]
    ],
];

The dir_name determines the root directory of the vfsStream for that particular Storage::disk(), I like to name it something relative to the actual disk name. Setting up the driver with env() allows us to default to our standard drivers or allow us to override that in phpunit.xml to switch over to the virtual filesystem driver.

Now, in your phpunit.xml add:

<env name="STORAGE_DATA_DRIVER" value="vfs"/>
<env name="S3_ARCHIVE_DRIVER" value="vfs"/>

That is all there is to it, those drives will now use the virtual filesystem adapter.