Test User creation

TestUser.cls

	public static void generateTestUser(String randomUserName){
        System.runAs ( new User(Id = UserInfo.getUserId()) ) {
            Profile p = [SELECT Id FROM Profile WHERE Name='Standard User'];
            User auxTestUser = new User();
            auxTestUser.Alias = 'standt';
            auxTestUser.Email = 'testemail@org.com';
            auxTestUser.EmailEncodingKey = 'UTF-8';
            auxTestUser.LastName = 'Test';
            auxTestUser.LanguageLocaleKey = 'en_US';
            auxTestUser.LocaleSidKey = 'en_US';
            auxTestUser.ProfileId = p.Id;
            auxTestUser.TimeZoneSidKey = 'America/Los_Angeles';
            auxTestUser.Username = randomUserName;
            insert auxTestUser;
        }
    }

To be used like this:

String randomUserName = 'TestUser@' + String.valueOf(System.currentTimeMillis()) + '.com';
generateTestUser(randomUserName);
ID ownerUserID = [SELECT ID FROM User WHERE Username = :randomUserName LIMIT 1][0].ID;