How to Test Laravel Socialite

I have an application that makes use of socialite, I want to create test for Github authentication, So I used Socialite Facade to mock call to the Socialite driver method, but when I run my test it tells me that I am trying to get value on null type.

Below is the test I have written

public function testGithubLogin()
{
    Socialite::shouldReceive('driver')
        ->with('github')
        ->once();
    $this->call('GET', '/github/authorize')->isRedirection();
}

Below is the implementation of the test

public function authorizeProvider($provider)
{
    return Socialite::driver($provider)->redirect();
}

I understand why it might return such result because Sociallite::driver($provider) returns an instance of Laravel\Socialite\Two\GithubProvider, and considering that I am unable to instantiate this value it will be impossible to specify a return type. I need help to successfully test the controller. Thanks