Need Help in writting Test Class when Permission set is assigned via Role??

UserRole role = new UserRole(DeveloperName = 'Sales Manager', Name = 'Sales Manager');
insert role;

User u = new User(
     ProfileId = [SELECT Id FROM Profile WHERE Name = 'YOUR PROFILE'].Id,
     LastName = 'last',
     Email = 'testtt@tessst.com',
     Username = 'testtt@tessst.com' + System.currentTimeMillis(),
     CompanyName = 'TEST',
     Title = 'title',
     Alias = 'alias',
     TimeZoneSidKey = 'America/Los_Angeles',
     EmailEncodingKey = 'UTF-8',
     LanguageLocaleKey = 'en_US',
     LocaleSidKey = 'en_US',
     UserRoleId = role.Id
);
Insert u;

PermissionSet perSet = [SELECT Id FROM PermissionSet WHERE Name='PERMISSION SET NAME'];

PermissionSetAssignment permAssnment = [SELECT Id, AssigneeId FROM PermissionSetAssignment WHERE AssigneeId= :u.Id LIMIT 1];

System.assertEquals(perSet.Id,permAssnment.PermissionSetId);