If you want to mock AR that doesn't try to connect to database you can do it in the following way (if using PHPUnit):
$post = $this->getMockBuilder('\app\model\Post')
->setMethods(['save', 'attributes'])
->getMock();
$post->method('save')->willReturn(true);
$post->method('attributes')->willReturn([
'id',
'status',
'title',
'description',
'text'
]);
The catch is that we need to override attributes() method since ActiveRecord by default is getting attributes list from database schema which we're trying to avoid.