Have I discovered something?!
Ok so I am 7dpo and couldn't resist testing. Because i am obsessed. Did a first response and it was negative. Line eyes kicked in. Turned the torch light on my phone and shone it behind the window and I could see a definite faint line of "darkness". Thought it may just be the test design so I opened he other unused one from the pack to shine the light behind that and the "second line of darkness" wasn't there. Any thoughts?! It's not an Evap because it's an actual line of darkness with lightness both sides.