SalesForce Book Mark

How to refer PageReference method from test class

https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages/pages_controller_error_handling.htm

https://developer.salesforce.com/docs/atlas.en-us.pages.meta/pages/pages_controller_error_handling.htm

Test Class 
https://developer.salesforce.com/page/An_Introduction_to_Apex_Code_Test_Methods


For OAUTH2
https://developer.salesforce.com/docs/atlas.en-us.api_rest.meta/api_rest/intro_understanding_username_password_oauth_flow.htm?search_text=grant_type