example.php

<?php

class EloquentDogRepository implements DogRepository {
	public function findBy($config)
	{
		return Dog::where(function($query) use($config) {
			foreach($config as $key => $value) {
				$query->where($key, '=', $value);
			}
		})->get();
	}
}

I prefer to use the opposite direction. In my tests I'm using another fresh database. Yes, I spend time in clearing the database, but I'm as close as possible to the real situation. When the project/test is simple, it's nice to use mocks, but if you have some complex integration test, which perform dozen of things in the data is better to use a real database. If the database is completely new for the tests you still can run the tests independently/parallel and leave the original one.