1 check if default window size is correct
2 check if child window size is correct
3 check if there is any field on page with default focus(in general, the focus should be set on first input field of the screen)
4 check if child windows are getting closed on closing parent/opener window
5 if child window is opened, user should not be able to use or update any field on background or parent window
6 check window minimize, maximize and close functionality
7 check if window is re-sizable
8 check scroll bar functionality for parent and child windows
9 check cancel button functionality for child window