Mechanism for unit testing without database?

Question

Yii

Yii2 uses ActiveRecord to work with the database, which is not testable. Therefore, we use a wrapper class that already uses ActiveRecord, and which can be capitulated.
Now the question arises, how to make the mock object work like an ActiveRecord, that is, have CRUD functions without using a database?
The simplest and fastest solution seems to be a mechanism using arrays.
For example, a request

$exists = User::find()->where(['username' => $username])->exists()

would be replaced by a function
(trivial example)

function exists($name, $value)
{
    $user = null;
    foreach($dbUsers as $dbUser) {
        if ($dbUser[$name] == $value) {
            return true;
        }
    }
    return false;
}

Are there such tools in php? And is the idea viable in principle?

Answer 1

Why don't you like the partial mock option? After all, you do not need to test CRUD as such, but the correct reaction of the surrounding code to how the ActiveRecord model behaves. Mock CRUD methods, let the rest work as is.

Answer 2

Pattern repository
in the working version
during testing

$PostRepository = new PostRepository($MemoryStorage);