You should do something like this:
$client_mock = \Mockery::mock('overload:App\Models\ModelName');
$client_mock->shouldReceive('create')->with($data)->andReturn($returnValue);
We use overload:it because you do not want to pass the layout to any class, but you want to use it in the case of hard coding in some classes.
In addition to your test class (before class) you should add:
, ( , , , ).
Mocking , .
UPDATE
, . ( orverload) :
App::instance('\App\Models\ModelName',$client_mock);