For file uploads in our application, we are utilizing ngFlow. With protractor being used for testing, we have several test case scenarios to validate such as unsupported file formats and maximum file size limitations. How can we effectively select files using protractor? While we can click the button to initiate the upload process, we encounter difficulty controlling the system file explorer. Although we can send keys to input type file, we are unsure how to trigger a submit action since there is no button within a form or a form being utilized.