Add assertUnprocessable to http tests (#7358)

* Add assertUnprocessable to http tests

* Update http-tests.md

Co-authored-by: Taylor Otwell <taylor@laravel.com>

http-tests.md

@@ -591,6 +591,7 @@ Laravel's `Illuminate\Testing\TestResponse` class provides a variety of custom a
 [assertStatus](#assert-status)
 [assertSuccessful](#assert-successful)
 [assertUnauthorized](#assert-unauthorized)
+[assertUnprocessable](#assert-unprocessable)
 [assertValid](#assert-valid)
 [assertInvalid](#assert-invalid)
 [assertViewHas](#assert-view-has)
@@ -999,6 +1000,13 @@ Assert that the response has an unauthorized (401) HTTP status code:
 
     $response->assertUnauthorized();
 
+<a name="assert-unprocessable"></a>
+#### assertUnprocessable
+
+Assert that the response has an unprocessable entity (422) HTTP status code:
+
+    $response->assertUnprocessable();
+
 <a name="assert-valid"></a>
 #### assertValid