function obtainClientGrant(APITester $I)
 {
     $client = factory(App\Models\OAuthClient::class, 1)->create();
     $grant = \App\Models\OAuthGrant::find('client_credentials');
     $client->oauth_grants()->attach($grant);
     $scope = \App\Models\OAuthScope::find('content');
     $client->oauth_scopes()->attach($scope);
     $I->wantTo('Send client credentials and receive an access token');
     $I->haveHttpHeader('Content-Type', 'application/x-www-form-urlencoded');
     $I->sendPOST('oauth/access_token', ['grant_type' => 'client_credentials', 'client_id' => $client->id, 'client_secret' => $client->secret, 'scope' => 'content']);
     $I->seeResponseCodeIs(200);
     $I->seeResponseIsJson();
     $I->seeResponseMatchesJsonType(['access_token' => 'string']);
 }