[8.x] Assert invalid

[taylorotwell]

Currently, there are two different ways to assert that a given response contains validation errors: assertSessionHasErrors and assertJsonValidationErrors.

You need to call the correct one depending on your response. In addition, they behave slightly differently - on JSON validation errors you may simply assert that the validation error contains a given string, while for session validation errors you must pass the entire validation error.

This PR introduces new assertValid and assertInvalid assertions to the TestResponse class that behaves similarly to the JSON validation error assertion in that you only need to provide a portion of the error message but it will work for both session validation errors and JSON response validation errors.

This allows you to always use assertValid / assertInvalid regardless of the type of response returned by your application.

$response->assertValid(['address']);

$response->assertInvalid(['name', 'email']);

$response->assertInvalid([
    'name' => 'required',
]);

[babacarcissedia]

Lovely API ❤️