Suggestion for status assertions

[tarreislam]

Hi

For assertStatus it would be more clean if the consts of Illuminate\Http\Response were used instead of integers.

Example

$response->assertStatus(200); -> $response->assertStatus(Response::HTTP_OK);
$response->assertStatus(400); -> $response->assertStatus(Response::HTTP_NOT_FOUND);
$response->assertStatus(422); -> $response->assertStatus(Response::HTTP_UNPROCESSABLE_ENTITY);