How to write a Test Class for the ConnectedAppPlugin Class?

@IsTest
public class ConnectedAppPluginExampleTest {
    @isTest
    public static void customAttributesTest(){
        Map<String,String> mapstr = new Map<String,String>();
        Test.startTest();
        ConnectedAppPluginExample  cap = new ConnectedAppPluginExample ();
        Map<String,String> respMapStr = cap.customAttributes(UserInfo.getUserId(),mapstr);
        Test.stopTest();
        Map<String,String> mapstrempty = new Map<String,String>();
        System.assertNotEquals(respMapStr,mapstrempty);
    }
}